Add a DiagnosticManager replace error streams in the expression parser.

We want to do a better job presenting errors that occur when evaluating
expressions. Key to this effort is getting away from a model where all
errors are spat out onto a stream where the client has to take or leave
all of them.

To this end, this patch adds a new class, DiagnosticManager, which
contains errors produced by the compiler or by LLDB as an expression
is created. The DiagnosticManager can dump itself to a log as well as
to a string. Clients will (in the future) be able to filter out the
errors they're interested in by ID or present subsets of these errors
to the user.

This patch is not intended to change the *users* of errors - only to
thread DiagnosticManagers to all the places where streams are used. I
also attempt to standardize our use of errors a bit, removing trailing
newlines and making clients omit 'error:', 'warning:' etc. and instead
pass the Severity flag.

The patch is testsuite-neutral, with modifications to one part of the
MI tests because it relied on "error: error:" being erroneously
printed. This patch fixes the MI variable handling and the testcase.

<rdar://problem/22864976>

32 files changed, 783 insertions, 607 deletions

diff --git a/lldb/source/Breakpoint/BreakpointLocation.cpp b/lldb/source/Breakpoint/BreakpointLocation.cpp
index 5ff91102aad..1d66d9dc6a4 100644
--- a/lldb/source/Breakpoint/BreakpointLocation.cpp
+++ b/lldb/source/Breakpoint/BreakpointLocation.cpp
@@ -19,6 +19,7 @@
 #include "lldb/Core/Module.h"
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/ValueObject.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/ExpressionVariable.h"
 #include "lldb/Expression/UserExpression.h"
 #include "lldb/Symbol/CompileUnit.h"
@@ -277,10 +278,10 @@ BreakpointLocation::ConditionSaysStop (ExecutionContext &exe_ctx, Error &error)
         m_user_expression_sp.reset();
         return false;
     }
-    
-    if (condition_hash != m_condition_hash ||
-        !m_user_expression_sp ||
-        !m_user_expression_sp->MatchesContext(exe_ctx))
+
+    DiagnosticManager diagnostics;
+
+    if (condition_hash != m_condition_hash || !m_user_expression_sp || !m_user_expression_sp->MatchesContext(exe_ctx))
     {
         LanguageType language = eLanguageTypeUnknown;
         // See if we can figure out the language from the frame, otherwise use the default language:
@@ -303,20 +304,14 @@ BreakpointLocation::ConditionSaysStop (ExecutionContext &exe_ctx, Error &error)
             return true;
         }
 
-        StreamString errors;
-        
-        if (!m_user_expression_sp->Parse(errors,
-                                         exe_ctx,
-                                         eExecutionPolicyOnlyWhenNeeded,
-                                         true,
-                                         false))
+        if (!m_user_expression_sp->Parse(diagnostics, exe_ctx, eExecutionPolicyOnlyWhenNeeded, true, false))
         {
             error.SetErrorStringWithFormat("Couldn't parse conditional expression:\n%s",
-                                           errors.GetData());
+                                           diagnostics.GetString().c_str());
             m_user_expression_sp.reset();
             return false;
         }
-        
+
         m_condition_hash = condition_hash;
     }
 
@@ -329,20 +324,16 @@ BreakpointLocation::ConditionSaysStop (ExecutionContext &exe_ctx, Error &error)
     options.SetUnwindOnError(true);
     options.SetIgnoreBreakpoints(true);
     options.SetTryAllThreads(true);
-    
+
     Error expr_error;
-    
-    StreamString execution_errors;
-    
+
+    diagnostics.Clear();
+
     ExpressionVariableSP result_variable_sp;
-    
+
     ExpressionResults result_code =
-    m_user_expression_sp->Execute(execution_errors,
-                                  exe_ctx,
-                                  options,
-                                  m_user_expression_sp,
-                                  result_variable_sp);
-    
+        m_user_expression_sp->Execute(diagnostics, exe_ctx, options, m_user_expression_sp, result_variable_sp);
+
     bool ret;
     
     if (result_code == eExpressionCompleted)
@@ -382,9 +373,9 @@ BreakpointLocation::ConditionSaysStop (ExecutionContext &exe_ctx, Error &error)
     else
     {
         ret = false;
-        error.SetErrorStringWithFormat("Couldn't execute expression:\n%s", execution_errors.GetData());
+        error.SetErrorStringWithFormat("Couldn't execute expression:\n%s", diagnostics.GetString().c_str());
     }
-    
+
     return ret;
 }
 
diff --git a/lldb/source/Expression/CMakeLists.txt b/lldb/source/Expression/CMakeLists.txt
index 52392f13319..48e67888e43 100644
--- a/lldb/source/Expression/CMakeLists.txt
+++ b/lldb/source/Expression/CMakeLists.txt
@@ -1,4 +1,5 @@
 add_lldb_library(lldbExpression
+  DiagnosticManager.cpp
   DWARFExpression.cpp
   Expression.cpp
   ExpressionSourceCode.cpp
diff --git a/lldb/source/Expression/DiagnosticManager.cpp b/lldb/source/Expression/DiagnosticManager.cpp
new file mode 100644
index 00000000000..8b788680936
--- /dev/null
+++ b/lldb/source/Expression/DiagnosticManager.cpp
@@ -0,0 +1,87 @@
+//===-- DiagnosticManager.cpp -----------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "lldb/Expression/DiagnosticManager.h"
+#include "lldb/Core/Log.h"
+#include "lldb/Core/StreamString.h"
+
+using namespace lldb_private;
+
+void
+DiagnosticManager::Dump(Log *log)
+{
+    if (!log)
+        return;
+
+    std::string str = GetString();
+
+    // GetString() puts a separator after each diagnostic.
+    // We want to remove the last '\n' because log->PutCString will add one for us.
+
+    if (str.size() && str.back() == '\n')
+    {
+        str.pop_back();
+    }
+
+    log->PutCString(str.c_str());
+}
+
+static const char *
+StringForSeverity(DiagnosticSeverity severity)
+{
+    switch (severity)
+    {
+        // this should be exhaustive
+        case lldb_private::eDiagnosticSeverityError:
+            return "error: ";
+        case lldb_private::eDiagnosticSeverityWarning:
+            return "warning: ";
+        case lldb_private::eDiagnosticSeverityRemark:
+            return "";
+    }
+}
+
+std::string
+DiagnosticManager::GetString(char separator)
+{
+    std::string ret;
+
+    for (const Diagnostic &diagnostic : Diagnostics())
+    {
+        ret.append(StringForSeverity(diagnostic.severity));
+        ret.append(diagnostic.message);
+        ret.push_back(separator);
+    }
+
+    return ret;
+}
+
+size_t
+DiagnosticManager::Printf(DiagnosticSeverity severity, const char *format, ...)
+{
+    StreamString ss;
+
+    va_list args;
+    va_start(args, format);
+    size_t result = ss.PrintfVarArg(format, args);
+    va_end(args);
+
+    AddDiagnostic(ss.GetData(), severity, eDiagnosticOriginLLDB);
+
+    return result;
+}
+
+size_t
+DiagnosticManager::PutCString(DiagnosticSeverity severity, const char *cstr)
+{
+    if (!cstr)
+        return 0;
+    AddDiagnostic(cstr, severity, eDiagnosticOriginLLDB);
+    return strlen(cstr);
+}
diff --git a/lldb/source/Expression/FunctionCaller.cpp b/lldb/source/Expression/FunctionCaller.cpp
index ddc378dcb41..0590c3b0d95 100644
--- a/lldb/source/Expression/FunctionCaller.cpp
+++ b/lldb/source/Expression/FunctionCaller.cpp
@@ -13,13 +13,14 @@
 // Other libraries and framework includes
 
 // Project includes
+#include "lldb/Expression/FunctionCaller.h"
 #include "lldb/Core/DataExtractor.h"
 #include "lldb/Core/Log.h"
 #include "lldb/Core/Module.h"
 #include "lldb/Core/State.h"
 #include "lldb/Core/ValueObject.h"
 #include "lldb/Core/ValueObjectList.h"
-#include "lldb/Expression/FunctionCaller.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/IRExecutionUnit.h"
 #include "lldb/Interpreter/CommandReturnObject.h"
 #include "lldb/Symbol/Function.h"
@@ -76,11 +77,11 @@ FunctionCaller::~FunctionCaller()
         lldb::ModuleSP jit_module_sp (m_jit_module_wp.lock());
         if (jit_module_sp)
             process_sp->GetTarget().GetImages().Remove(jit_module_sp);
-    }    
+    }
 }
 
 bool
-FunctionCaller::WriteFunctionWrapper (ExecutionContext &exe_ctx, Stream &errors)
+FunctionCaller::WriteFunctionWrapper(ExecutionContext &exe_ctx, DiagnosticManager &diagnostic_manager)
 {
     Process *process = exe_ctx.GetProcessPtr();
 
@@ -133,27 +134,28 @@ FunctionCaller::WriteFunctionWrapper (ExecutionContext &exe_ctx, Stream &errors)
 }
 
 bool
-FunctionCaller::WriteFunctionArguments (ExecutionContext &exe_ctx, lldb::addr_t &args_addr_ref, Stream &errors)
+FunctionCaller::WriteFunctionArguments(ExecutionContext &exe_ctx, lldb::addr_t &args_addr_ref,
+                                       DiagnosticManager &diagnostic_manager)
 {
-    return WriteFunctionArguments(exe_ctx, args_addr_ref, m_arg_values, errors);
+    return WriteFunctionArguments(exe_ctx, args_addr_ref, m_arg_values, diagnostic_manager);
 }
 
 // FIXME: Assure that the ValueList we were passed in is consistent with the one that defined this function.
 
 bool
-FunctionCaller::WriteFunctionArguments (ExecutionContext &exe_ctx, 
-                                       lldb::addr_t &args_addr_ref, 
-                                       ValueList &arg_values,
-                                       Stream &errors)
+FunctionCaller::WriteFunctionArguments(ExecutionContext &exe_ctx, lldb::addr_t &args_addr_ref, ValueList &arg_values,
+                                       DiagnosticManager &diagnostic_manager)
 {
     // All the information to reconstruct the struct is provided by the
     // StructExtractor.
     if (!m_struct_valid)
     {
-        errors.Printf("Argument information was not correctly parsed, so the function cannot be called.");
+        diagnostic_manager.PutCString(
+            eDiagnosticSeverityError,
+            "Argument information was not correctly parsed, so the function cannot be called.");
         return false;
     }
-        
+
     Error error;
     lldb::ExpressionResults return_value = lldb::eExpressionSetupError;
 
@@ -191,14 +193,16 @@ FunctionCaller::WriteFunctionArguments (ExecutionContext &exe_ctx,
     // FIXME: We will need to extend this for Variadic functions.
 
     Error value_error;
-    
+
     size_t num_args = arg_values.GetSize();
     if (num_args != m_arg_values.GetSize())
     {
-        errors.Printf ("Wrong number of arguments - was: %" PRIu64 " should be: %" PRIu64 "", (uint64_t)num_args, (uint64_t)m_arg_values.GetSize());
+        diagnostic_manager.Printf(eDiagnosticSeverityError,
+                                  "Wrong number of arguments - was: %" PRIu64 " should be: %" PRIu64 "",
+                                  (uint64_t)num_args, (uint64_t)m_arg_values.GetSize());
         return false;
     }
-    
+
     for (size_t i = 0; i < num_args; i++)
     {
         // FIXME: We should sanity check sizes.
@@ -225,16 +229,17 @@ FunctionCaller::WriteFunctionArguments (ExecutionContext &exe_ctx,
 }
 
 bool
-FunctionCaller::InsertFunction (ExecutionContext &exe_ctx, lldb::addr_t &args_addr_ref, Stream &errors)
+FunctionCaller::InsertFunction(ExecutionContext &exe_ctx, lldb::addr_t &args_addr_ref,
+                               DiagnosticManager &diagnostic_manager)
 {
-    if (CompileFunction(errors) != 0)
+    if (CompileFunction(diagnostic_manager) != 0)
         return false;
-    if (!WriteFunctionWrapper(exe_ctx, errors))
+    if (!WriteFunctionWrapper(exe_ctx, diagnostic_manager))
         return false;
-    if (!WriteFunctionArguments(exe_ctx, args_addr_ref, errors))
+    if (!WriteFunctionArguments(exe_ctx, args_addr_ref, diagnostic_manager))
         return false;
 
-    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_STEP));
+    Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
     if (log)
         log->Printf ("Call Address: 0x%" PRIx64 " Struct Address: 0x%" PRIx64 ".\n", m_jit_start_addr, args_addr_ref);
         
@@ -242,13 +247,12 @@ FunctionCaller::InsertFunction (ExecutionContext &exe_ctx, lldb::addr_t &args_ad
 }
 
 lldb::ThreadPlanSP
-FunctionCaller::GetThreadPlanToCallFunction (ExecutionContext &exe_ctx, 
-                                            lldb::addr_t args_addr,
+FunctionCaller::GetThreadPlanToCallFunction(ExecutionContext &exe_ctx, lldb::addr_t args_addr,
                                             const EvaluateExpressionOptions &options,
-                                            Stream &errors)
+                                            DiagnosticManager &diagnostic_manager)
 {
-    Log *log(lldb_private::GetLogIfAnyCategoriesSet (LIBLLDB_LOG_EXPRESSIONS | LIBLLDB_LOG_STEP));
-    
+    Log *log(lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_EXPRESSIONS | LIBLLDB_LOG_STEP));
+
     if (log)
         log->Printf("-- [FunctionCaller::GetThreadPlanToCallFunction] Creating thread plan to call function \"%s\" --", m_name.c_str());
     
@@ -256,7 +260,7 @@ FunctionCaller::GetThreadPlanToCallFunction (ExecutionContext &exe_ctx,
     Thread *thread = exe_ctx.GetThreadPtr();
     if (thread == NULL)
     {
-        errors.Printf("Can't call a function without a valid thread.");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "Can't call a function without a valid thread.");
         return NULL;
     }
 
@@ -322,15 +326,12 @@ FunctionCaller::DeallocateFunctionResults (ExecutionContext &exe_ctx, lldb::addr
 }
 
 lldb::ExpressionResults
-FunctionCaller::ExecuteFunction(
-        ExecutionContext &exe_ctx, 
-        lldb::addr_t *args_addr_ptr,
-        const EvaluateExpressionOptions &options,
-        Stream &errors, 
-        Value &results)
+FunctionCaller::ExecuteFunction(ExecutionContext &exe_ctx, lldb::addr_t *args_addr_ptr,
+                                const EvaluateExpressionOptions &options, DiagnosticManager &diagnostic_manager,
+                                Value &results)
 {
     lldb::ExpressionResults return_value = lldb::eExpressionSetupError;
-    
+
     // FunctionCaller::ExecuteFunction execution is always just to get the result.  Do make sure we ignore
     // breakpoints, unwind on error, and don't try to debug it.
     EvaluateExpressionOptions real_options = options;
@@ -344,13 +345,13 @@ FunctionCaller::ExecuteFunction(
         args_addr = *args_addr_ptr;
     else
         args_addr = LLDB_INVALID_ADDRESS;
-        
-    if (CompileFunction(errors) != 0)
+
+    if (CompileFunction(diagnostic_manager) != 0)
         return lldb::eExpressionSetupError;
-    
+
     if (args_addr == LLDB_INVALID_ADDRESS)
     {
-        if (!InsertFunction(exe_ctx, args_addr, errors))
+        if (!InsertFunction(exe_ctx, args_addr, diagnostic_manager))
             return lldb::eExpressionSetupError;
     }
 
@@ -358,24 +359,18 @@ FunctionCaller::ExecuteFunction(
 
     if (log)
         log->Printf("== [FunctionCaller::ExecuteFunction] Executing function \"%s\" ==", m_name.c_str());
-    
-    lldb::ThreadPlanSP call_plan_sp = GetThreadPlanToCallFunction (exe_ctx,
-                                                                   args_addr,
-                                                                   real_options,
-                                                                   errors);
+
+    lldb::ThreadPlanSP call_plan_sp = GetThreadPlanToCallFunction(exe_ctx, args_addr, real_options, diagnostic_manager);
     if (!call_plan_sp)
         return lldb::eExpressionSetupError;
-        
+
     // We need to make sure we record the fact that we are running an expression here
     // otherwise this fact will fail to be recorded when fetching an Objective-C object description
     if (exe_ctx.GetProcessPtr())
         exe_ctx.GetProcessPtr()->SetRunningUserExpression(true);
-    
-    return_value = exe_ctx.GetProcessRef().RunThreadPlan (exe_ctx,
-                                                          call_plan_sp,
-                                                          real_options,
-                                                          errors);
-    
+
+    return_value = exe_ctx.GetProcessRef().RunThreadPlan(exe_ctx, call_plan_sp, real_options, diagnostic_manager);
+
     if (log)
     {
         if (return_value != lldb::eExpressionCompleted)
diff --git a/lldb/source/Expression/IRDynamicChecks.cpp b/lldb/source/Expression/IRDynamicChecks.cpp
index c2195de4d44..62bcfe0d14b 100644
--- a/lldb/source/Expression/IRDynamicChecks.cpp
+++ b/lldb/source/Expression/IRDynamicChecks.cpp
@@ -50,8 +50,7 @@ DynamicCheckerFunctions::DynamicCheckerFunctions() = default;
 DynamicCheckerFunctions::~DynamicCheckerFunctions() = default;
 
 bool
-DynamicCheckerFunctions::Install(Stream &error_stream,
-                                 ExecutionContext &exe_ctx)
+DynamicCheckerFunctions::Install(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx)
 {
     Error error;
     m_valid_pointer_check.reset(exe_ctx.GetTargetRef().GetUtilityFunctionForLanguage(g_valid_pointer_check_text,
@@ -60,8 +59,8 @@ DynamicCheckerFunctions::Install(Stream &error_stream,
                                                                                      error));
     if (error.Fail())
         return false;
-        
-    if (!m_valid_pointer_check->Install(error_stream, exe_ctx))
+
+    if (!m_valid_pointer_check->Install(diagnostic_manager, exe_ctx))
         return false;
 
     Process *process = exe_ctx.GetProcessPtr();
@@ -74,7 +73,7 @@ DynamicCheckerFunctions::Install(Stream &error_stream,
         {
             m_objc_object_check.reset(objc_language_runtime->CreateObjectChecker(VALID_OBJC_OBJECT_CHECK_NAME));
 
-            if (!m_objc_object_check->Install(error_stream, exe_ctx))
+            if (!m_objc_object_check->Install(diagnostic_manager, exe_ctx))
                 return false;
         }
     }
diff --git a/lldb/source/Expression/IRInterpreter.cpp b/lldb/source/Expression/IRInterpreter.cpp
index fef6c57ba23..a0d7a163a92 100644
--- a/lldb/source/Expression/IRInterpreter.cpp
+++ b/lldb/source/Expression/IRInterpreter.cpp
@@ -7,18 +7,19 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "lldb/Expression/IRInterpreter.h"
 #include "lldb/Core/ConstString.h"
 #include "lldb/Core/DataExtractor.h"
 #include "lldb/Core/Error.h"
 #include "lldb/Core/Log.h"
-#include "lldb/Core/ModuleSpec.h"
 #include "lldb/Core/Module.h"
+#include "lldb/Core/ModuleSpec.h"
 #include "lldb/Core/Scalar.h"
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/ValueObject.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/IRExecutionUnit.h"
 #include "lldb/Expression/IRMemoryMap.h"
-#include "lldb/Expression/IRInterpreter.h"
 #include "lldb/Host/Endian.h"
 
 #include "lldb/Target/ABI.h"
@@ -1596,7 +1597,7 @@ IRInterpreter::Interpret (llvm::Module &module,
                 }
                 lldb_private::Address funcAddr(I.ULongLong(LLDB_INVALID_ADDRESS));
 
-                lldb_private::StreamString error_stream;
+                lldb_private::DiagnosticManager diagnostics;
                 lldb_private::EvaluateExpressionOptions options;
 
                 // We generally receive a function pointer which we must dereference
@@ -1701,31 +1702,24 @@ IRInterpreter::Interpret (llvm::Module &module,
                 llvm::ArrayRef<lldb_private::ABI::CallArgument> args(rawArgs, numArgs);
 
                 // Setup a thread plan to call the target function
-                lldb::ThreadPlanSP call_plan_sp
-                (
-                    new lldb_private::ThreadPlanCallFunctionUsingABI
-                    (
-                        exe_ctx.GetThreadRef(),
-                        funcAddr,
-                        *prototype,
-                        *returnType,
-                        args,
-                        options
-                    )
-                );
+                lldb::ThreadPlanSP call_plan_sp(new lldb_private::ThreadPlanCallFunctionUsingABI(
+                    exe_ctx.GetThreadRef(), funcAddr, *prototype, *returnType, args, options));
 
                 // Check if the plan is valid
-                if (!call_plan_sp || !call_plan_sp->ValidatePlan(&error_stream))
+                lldb_private::StreamString ss;
+                if (!call_plan_sp || !call_plan_sp->ValidatePlan(&ss))
                 {
                     error.SetErrorToGenericError();
-                    error.SetErrorStringWithFormat("unable to make ThreadPlanCallFunctionUsingABI for 0x%llx", I.ULongLong());
+                    error.SetErrorStringWithFormat("unable to make ThreadPlanCallFunctionUsingABI for 0x%llx",
+                                                   I.ULongLong());
                     return false;
                 }
 
                 exe_ctx.GetProcessPtr()->SetRunningUserExpression(true);
 
                 // Execute the actual function call thread plan
-                lldb::ExpressionResults res = exe_ctx.GetProcessRef().RunThreadPlan(exe_ctx, call_plan_sp, options, error_stream);
+                lldb::ExpressionResults res =
+                    exe_ctx.GetProcessRef().RunThreadPlan(exe_ctx, call_plan_sp, options, diagnostics);
 
                 // Check that the thread plan completed successfully
                 if (res != lldb::ExpressionResults::eExpressionCompleted)
diff --git a/lldb/source/Expression/LLVMUserExpression.cpp b/lldb/source/Expression/LLVMUserExpression.cpp
index bdb50408518..3c42a540535 100644
--- a/lldb/source/Expression/LLVMUserExpression.cpp
+++ b/lldb/source/Expression/LLVMUserExpression.cpp
@@ -18,6 +18,7 @@
 #include "lldb/Core/StreamFile.h"
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/ValueObjectConstResult.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/ExpressionSourceCode.h"
 #include "lldb/Expression/IRExecutionUnit.h"
 #include "lldb/Expression/IRInterpreter.h"
@@ -25,11 +26,11 @@
 #include "lldb/Host/HostInfo.h"
 #include "lldb/Symbol/Block.h"
 #include "lldb/Symbol/ClangASTContext.h"
+#include "lldb/Symbol/ClangExternalASTSourceCommon.h"
 #include "lldb/Symbol/Function.h"
 #include "lldb/Symbol/ObjectFile.h"
 #include "lldb/Symbol/SymbolVendor.h"
 #include "lldb/Symbol/Type.h"
-#include "lldb/Symbol/ClangExternalASTSourceCommon.h"
 #include "lldb/Symbol/VariableList.h"
 #include "lldb/Target/ExecutionContext.h"
 #include "lldb/Target/Process.h"
@@ -76,8 +77,9 @@ LLVMUserExpression::~LLVMUserExpression()
 }
 
 lldb::ExpressionResults
-LLVMUserExpression::Execute(Stream &error_stream, ExecutionContext &exe_ctx, const EvaluateExpressionOptions &options,
-                            lldb::UserExpressionSP &shared_ptr_to_me, lldb::ExpressionVariableSP &result)
+LLVMUserExpression::Execute(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+                            const EvaluateExpressionOptions &options, lldb::UserExpressionSP &shared_ptr_to_me,
+                            lldb::ExpressionVariableSP &result)
 {
     // The expression log is quite verbose, and if you're just tracking the execution of the
     // expression, it's quite convenient to have these logs come out with the STEP log as well.
@@ -87,9 +89,10 @@ LLVMUserExpression::Execute(Stream &error_stream, ExecutionContext &exe_ctx, con
     {
         lldb::addr_t struct_address = LLDB_INVALID_ADDRESS;
 
-        if (!PrepareToExecuteJITExpression(error_stream, exe_ctx, struct_address))
+        if (!PrepareToExecuteJITExpression(diagnostic_manager, exe_ctx, struct_address))
         {
-            error_stream.Printf("Errored out in %s, couldn't PrepareToExecuteJITExpression", __FUNCTION__);
+            diagnostic_manager.Printf(eDiagnosticSeverityError,
+                                      "errored out in %s, couldn't PrepareToExecuteJITExpression", __FUNCTION__);
             return lldb::eExpressionSetupError;
         }
 
@@ -103,7 +106,7 @@ LLVMUserExpression::Execute(Stream &error_stream, ExecutionContext &exe_ctx, con
 
             if (!module || !function)
             {
-                error_stream.Printf("Supposed to interpret, but nothing is there");
+                diagnostic_manager.PutCString(eDiagnosticSeverityError, "supposed to interpret, but nothing is there");
                 return lldb::eExpressionSetupError;
             }
 
@@ -111,9 +114,10 @@ LLVMUserExpression::Execute(Stream &error_stream, ExecutionContext &exe_ctx, con
 
             std::vector<lldb::addr_t> args;
 
-            if (!AddArguments(exe_ctx, args, struct_address, error_stream))
+            if (!AddArguments(exe_ctx, args, struct_address, diagnostic_manager))
             {
-                error_stream.Printf("Errored out in %s, couldn't AddArguments", __FUNCTION__);
+                diagnostic_manager.Printf(eDiagnosticSeverityError, "errored out in %s, couldn't AddArguments",
+                                          __FUNCTION__);
                 return lldb::eExpressionSetupError;
             }
 
@@ -125,7 +129,8 @@ LLVMUserExpression::Execute(Stream &error_stream, ExecutionContext &exe_ctx, con
 
             if (!interpreter_error.Success())
             {
-                error_stream.Printf("Supposed to interpret, but failed: %s", interpreter_error.AsCString());
+                diagnostic_manager.Printf(eDiagnosticSeverityError, "supposed to interpret, but failed: %s",
+                                          interpreter_error.AsCString());
                 return lldb::eExpressionDiscarded;
             }
         }
@@ -133,7 +138,7 @@ LLVMUserExpression::Execute(Stream &error_stream, ExecutionContext &exe_ctx, con
         {
             if (!exe_ctx.HasThreadScope())
             {
-                error_stream.Printf("UserExpression::Execute called with no thread selected.");
+                diagnostic_manager.Printf(eDiagnosticSeverityError, "%s called with no thread selected", __FUNCTION__);
                 return lldb::eExpressionSetupError;
             }
 
@@ -141,17 +146,22 @@ LLVMUserExpression::Execute(Stream &error_stream, ExecutionContext &exe_ctx, con
 
             std::vector<lldb::addr_t> args;
 
-            if (!AddArguments(exe_ctx, args, struct_address, error_stream))
+            if (!AddArguments(exe_ctx, args, struct_address, diagnostic_manager))
             {
-                error_stream.Printf("Errored out in %s, couldn't AddArguments", __FUNCTION__);
+                diagnostic_manager.Printf(eDiagnosticSeverityError, "errored out in %s, couldn't AddArguments",
+                                          __FUNCTION__);
                 return lldb::eExpressionSetupError;
             }
 
             lldb::ThreadPlanSP call_plan_sp(new ThreadPlanCallUserExpression(exe_ctx.GetThreadRef(), wrapper_address,
                                                                              args, options, shared_ptr_to_me));
 
-            if (!call_plan_sp || !call_plan_sp->ValidatePlan(&error_stream))
+            StreamString ss;
+            if (!call_plan_sp || !call_plan_sp->ValidatePlan(&ss))
+            {
+                diagnostic_manager.PutCString(eDiagnosticSeverityError, ss.GetData());
                 return lldb::eExpressionSetupError;
+            }
 
             ThreadPlanCallUserExpression *user_expression_plan =
                 static_cast<ThreadPlanCallUserExpression *>(call_plan_sp.get());
@@ -168,7 +178,7 @@ LLVMUserExpression::Execute(Stream &error_stream, ExecutionContext &exe_ctx, con
                 exe_ctx.GetProcessPtr()->SetRunningUserExpression(true);
 
             lldb::ExpressionResults execution_result =
-                exe_ctx.GetProcessRef().RunThreadPlan(exe_ctx, call_plan_sp, options, error_stream);
+                exe_ctx.GetProcessRef().RunThreadPlan(exe_ctx, call_plan_sp, options, diagnostic_manager);
 
             if (exe_ctx.GetProcessPtr())
                 exe_ctx.GetProcessPtr()->SetRunningUserExpression(false);
@@ -187,20 +197,21 @@ LLVMUserExpression::Execute(Stream &error_stream, ExecutionContext &exe_ctx, con
                         error_desc = real_stop_info_sp->GetDescription();
                 }
                 if (error_desc)
-                    error_stream.Printf("Execution was interrupted, reason: %s.", error_desc);
+                    diagnostic_manager.Printf(eDiagnosticSeverityError, "Execution was interrupted, reason: %s.",
+                                              error_desc);
                 else
-                    error_stream.PutCString("Execution was interrupted.");
+                    diagnostic_manager.PutCString(eDiagnosticSeverityError, "Execution was interrupted.");
 
                 if ((execution_result == lldb::eExpressionInterrupted && options.DoesUnwindOnError()) ||
                     (execution_result == lldb::eExpressionHitBreakpoint && options.DoesIgnoreBreakpoints()))
-                    error_stream.PutCString(
-                        "\nThe process has been returned to the state before expression evaluation.");
+                    diagnostic_manager.AppendMessageToDiagnostic(
+                        "The process has been returned to the state before expression evaluation.");
                 else
                 {
                     if (execution_result == lldb::eExpressionHitBreakpoint)
                         user_expression_plan->TransferExpressionOwnership();
-                    error_stream.PutCString(
-                        "\nThe process has been left at the point where it was interrupted, "
+                    diagnostic_manager.AppendMessageToDiagnostic(
+                        "The process has been left at the point where it was interrupted, "
                         "use \"thread return -x\" to return to the state before expression evaluation.");
                 }
 
@@ -208,7 +219,8 @@ LLVMUserExpression::Execute(Stream &error_stream, ExecutionContext &exe_ctx, con
             }
             else if (execution_result == lldb::eExpressionStoppedForDebug)
             {
-                error_stream.PutCString(
+                diagnostic_manager.PutCString(
+                    eDiagnosticSeverityRemark,
                     "Execution was halted at the first instruction of the expression "
                     "function because \"debug\" was requested.\n"
                     "Use \"thread return -x\" to return to the state before expression evaluation.");
@@ -216,13 +228,13 @@ LLVMUserExpression::Execute(Stream &error_stream, ExecutionContext &exe_ctx, con
             }
             else if (execution_result != lldb::eExpressionCompleted)
             {
-                error_stream.Printf("Couldn't execute function; result was %s\n",
-                                    Process::ExecutionResultAsCString(execution_result));
+                diagnostic_manager.Printf(eDiagnosticSeverityError, "Couldn't execute function; result was %s",
+                                          Process::ExecutionResultAsCString(execution_result));
                 return execution_result;
             }
         }
 
-        if (FinalizeJITExecution(error_stream, exe_ctx, result, function_stack_bottom, function_stack_top))
+        if (FinalizeJITExecution(diagnostic_manager, exe_ctx, result, function_stack_bottom, function_stack_top))
         {
             return lldb::eExpressionCompleted;
         }
@@ -233,13 +245,14 @@ LLVMUserExpression::Execute(Stream &error_stream, ExecutionContext &exe_ctx, con
     }
     else
     {
-        error_stream.Printf("Expression can't be run, because there is no JIT compiled function");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError,
+                                      "Expression can't be run, because there is no JIT compiled function");
         return lldb::eExpressionSetupError;
     }
 }
 
 bool
-LLVMUserExpression::FinalizeJITExecution(Stream &error_stream, ExecutionContext &exe_ctx,
+LLVMUserExpression::FinalizeJITExecution(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
                                          lldb::ExpressionVariableSP &result, lldb::addr_t function_stack_bottom,
                                          lldb::addr_t function_stack_top)
 {
@@ -250,7 +263,8 @@ LLVMUserExpression::FinalizeJITExecution(Stream &error_stream, ExecutionContext
 
     if (!m_dematerializer_sp)
     {
-        error_stream.Printf("Couldn't apply expression side effects : no dematerializer is present");
+        diagnostic_manager.Printf(eDiagnosticSeverityError,
+                                  "Couldn't apply expression side effects : no dematerializer is present");
         return false;
     }
 
@@ -260,8 +274,8 @@ LLVMUserExpression::FinalizeJITExecution(Stream &error_stream, ExecutionContext
 
     if (!dematerialize_error.Success())
     {
-        error_stream.Printf("Couldn't apply expression side effects : %s\n",
-                            dematerialize_error.AsCString("unknown error"));
+        diagnostic_manager.Printf(eDiagnosticSeverityError, "Couldn't apply expression side effects : %s",
+                                  dematerialize_error.AsCString("unknown error"));
         return false;
     }
 
@@ -276,7 +290,7 @@ LLVMUserExpression::FinalizeJITExecution(Stream &error_stream, ExecutionContext
 }
 
 bool
-LLVMUserExpression::PrepareToExecuteJITExpression(Stream &error_stream, ExecutionContext &exe_ctx,
+LLVMUserExpression::PrepareToExecuteJITExpression(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
                                                   lldb::addr_t &struct_address)
 {
     lldb::TargetSP target;
@@ -285,7 +299,8 @@ LLVMUserExpression::PrepareToExecuteJITExpression(Stream &error_stream, Executio
 
     if (!LockAndCheckContext(exe_ctx, target, process, frame))
     {
-        error_stream.Printf("The context has changed before we could JIT the expression!\n");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError,
+                                      "The context has changed before we could JIT the expression!");
         return false;
     }
 
@@ -309,7 +324,9 @@ LLVMUserExpression::PrepareToExecuteJITExpression(Stream &error_stream, Executio
 
             if (!alloc_error.Success())
             {
-                error_stream.Printf("Couldn't allocate space for materialized struct: %s\n", alloc_error.AsCString());
+                diagnostic_manager.Printf(eDiagnosticSeverityError,
+                                          "Couldn't allocate space for materialized struct: %s",
+                                          alloc_error.AsCString());
                 return false;
             }
         }
@@ -335,7 +352,8 @@ LLVMUserExpression::PrepareToExecuteJITExpression(Stream &error_stream, Executio
 
             if (!alloc_error.Success())
             {
-                error_stream.Printf("Couldn't allocate space for the stack frame: %s\n", alloc_error.AsCString());
+                diagnostic_manager.Printf(eDiagnosticSeverityError, "Couldn't allocate space for the stack frame: %s",
+                                          alloc_error.AsCString());
                 return false;
             }
         }
@@ -347,7 +365,8 @@ LLVMUserExpression::PrepareToExecuteJITExpression(Stream &error_stream, Executio
 
         if (!materialize_error.Success())
         {
-            error_stream.Printf("Couldn't materialize: %s\n", materialize_error.AsCString());
+            diagnostic_manager.Printf(eDiagnosticSeverityError, "Couldn't materialize: %s",
+                                      materialize_error.AsCString());
             return false;
         }
     }
diff --git a/lldb/source/Expression/UserExpression.cpp b/lldb/source/Expression/UserExpression.cpp
index 70f004ba25c..6b97eb68b11 100644
--- a/lldb/source/Expression/UserExpression.cpp
+++ b/lldb/source/Expression/UserExpression.cpp
@@ -16,18 +16,19 @@
 #include <string>
 #include <map>
 
+#include "Plugins/ExpressionParser/Clang/ClangPersistentVariables.h"
 #include "lldb/Core/ConstString.h"
 #include "lldb/Core/Log.h"
 #include "lldb/Core/Module.h"
 #include "lldb/Core/StreamFile.h"
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/ValueObjectConstResult.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/ExpressionSourceCode.h"
 #include "lldb/Expression/IRExecutionUnit.h"
 #include "lldb/Expression/IRInterpreter.h"
 #include "lldb/Expression/Materializer.h"
 #include "lldb/Expression/UserExpression.h"
-#include "Plugins/ExpressionParser/Clang/ClangPersistentVariables.h"
 #include "lldb/Host/HostInfo.h"
 #include "lldb/Symbol/Block.h"
 #include "lldb/Symbol/Function.h"
@@ -232,8 +233,6 @@ UserExpression::Evaluate (ExecutionContext &exe_ctx,
             log->Printf ("== [UserExpression::Evaluate] Getting expression: %s ==", error.AsCString());
         return lldb::eExpressionSetupError;
     }
- 
-    StreamString error_stream;
 
     if (log)
         log->Printf("== [UserExpression::Evaluate] Parsing expression %s ==", expr_cstr);
@@ -244,21 +243,20 @@ UserExpression::Evaluate (ExecutionContext &exe_ctx,
     if (options.InvokeCancelCallback (lldb::eExpressionEvaluationParse))
     {
         error.SetErrorString ("expression interrupted by callback before parse");
-        result_valobj_sp = ValueObjectConstResult::Create (exe_ctx.GetBestExecutionContextScope(), error);
+        result_valobj_sp = ValueObjectConstResult::Create(exe_ctx.GetBestExecutionContextScope(), error);
         return lldb::eExpressionInterrupted;
     }
 
-    if (!user_expression_sp->Parse (error_stream,
-                                    exe_ctx,
-                                    execution_policy,
-                                    keep_expression_in_memory,
-                                    generate_debug_info))
+    DiagnosticManager diagnostic_manager;
+
+    if (!user_expression_sp->Parse(diagnostic_manager, exe_ctx, execution_policy, keep_expression_in_memory,
+                                   generate_debug_info))
     {
         execution_results = lldb::eExpressionParseError;
-        if (error_stream.GetString().empty())
-            error.SetExpressionError (execution_results, "expression failed to parse, unknown error");
+        if (!diagnostic_manager.Diagnostics().size())
+            error.SetExpressionError(execution_results, "expression failed to parse, unknown error");
         else
-            error.SetExpressionError (execution_results, error_stream.GetString().c_str());
+            error.SetExpressionError(execution_results, diagnostic_manager.GetString().c_str());
     }
     else
     {
@@ -274,8 +272,8 @@ UserExpression::Evaluate (ExecutionContext &exe_ctx,
             if (log)
                 log->Printf("== [UserExpression::Evaluate] Expression may not run, but is not constant ==");
 
-            if (error_stream.GetString().empty())
-                error.SetExpressionError (lldb::eExpressionSetupError, "expression needed to run but couldn't");
+            if (!diagnostic_manager.Diagnostics().size())
+                error.SetExpressionError(lldb::eExpressionSetupError, "expression needed to run but couldn't");
         }
         else
         {
@@ -286,16 +284,13 @@ UserExpression::Evaluate (ExecutionContext &exe_ctx,
                 return lldb::eExpressionInterrupted;
             }
 
-            error_stream.GetString().clear();
+            diagnostic_manager.Clear();
 
             if (log)
                 log->Printf("== [UserExpression::Evaluate] Executing expression ==");
 
-            execution_results = user_expression_sp->Execute (error_stream,
-                                                             exe_ctx,
-                                                             options,
-                                                             user_expression_sp,
-                                                             expr_result);
+            execution_results =
+                user_expression_sp->Execute(diagnostic_manager, exe_ctx, options, user_expression_sp, expr_result);
 
             if (options.GetResultIsInternal() && expr_result && process)
             {
@@ -307,10 +302,10 @@ UserExpression::Evaluate (ExecutionContext &exe_ctx,
                 if (log)
                     log->Printf("== [UserExpression::Evaluate] Execution completed abnormally ==");
 
-                if (error_stream.GetString().empty())
-                    error.SetExpressionError (execution_results, "expression failed to execute, unknown error");
+                if (!diagnostic_manager.Diagnostics().size())
+                    error.SetExpressionError(execution_results, "expression failed to execute, unknown error");
                 else
-                    error.SetExpressionError (execution_results, error_stream.GetString().c_str());
+                    error.SetExpressionError(execution_results, diagnostic_manager.GetString().c_str());
             }
             else
             {
diff --git a/lldb/source/Expression/UtilityFunction.cpp b/lldb/source/Expression/UtilityFunction.cpp
index f93e358d35d..78059615578 100644
--- a/lldb/source/Expression/UtilityFunction.cpp
+++ b/lldb/source/Expression/UtilityFunction.cpp
@@ -20,10 +20,11 @@
 #include "lldb/Core/Module.h"
 #include "lldb/Core/Stream.h"
 #include "lldb/Core/StreamFile.h"
-#include "lldb/Expression/FunctionCaller.h"
-#include "lldb/Expression/UtilityFunction.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/ExpressionSourceCode.h"
+#include "lldb/Expression/FunctionCaller.h"
 #include "lldb/Expression/IRExecutionUnit.h"
+#include "lldb/Expression/UtilityFunction.h"
 #include "lldb/Host/Host.h"
 #include "lldb/Target/ExecutionContext.h"
 #include "lldb/Target/Process.h"
@@ -96,26 +97,24 @@ UtilityFunction::MakeFunctionCaller (const CompilerType &return_type, const Valu
     }
     if (m_caller_up)
     {
-        StreamString errors;
-        errors.Clear();
-        unsigned num_errors = m_caller_up->CompileFunction(errors);
+        DiagnosticManager diagnostics;
+
+        unsigned num_errors = m_caller_up->CompileFunction(diagnostics);
         if (num_errors)
         {
-            error.SetErrorStringWithFormat ("Error compiling %s caller function: \"%s\".",
-                                                m_function_name.c_str(),
-                                                errors.GetData());
+            error.SetErrorStringWithFormat("Error compiling %s caller function: \"%s\".", m_function_name.c_str(),
+                                           diagnostics.GetString().c_str());
             m_caller_up.reset();
             return nullptr;
         }
-        
-        errors.Clear();
+
+        diagnostics.Clear();
         ExecutionContext exe_ctx(process_sp);
-        
-        if (!m_caller_up->WriteFunctionWrapper(exe_ctx, errors))
+
+        if (!m_caller_up->WriteFunctionWrapper(exe_ctx, diagnostics))
         {
-            error.SetErrorStringWithFormat ("Error inserting caller function for %s: \"%s\".",
-                                                m_function_name.c_str(),
-                                                errors.GetData());
+            error.SetErrorStringWithFormat("Error inserting caller function for %s: \"%s\".", m_function_name.c_str(),
+                                           diagnostics.GetString().c_str());
             m_caller_up.reset();
             return nullptr;
         }
diff --git a/lldb/source/Host/macosx/Host.mm b/lldb/source/Host/macosx/Host.mm
index 2db27a276e4..7f559fd79b8 100644
--- a/lldb/source/Host/macosx/Host.mm
+++ b/lldb/source/Host/macosx/Host.mm
@@ -1448,6 +1448,8 @@ Host::ShellExpandArguments (ProcessLaunchInfo &launch_info)
     return error;
 }
 
+#include <thread>
+
 HostThread
 Host::StartMonitoringChildProcess(Host::MonitorChildProcessCallback callback, void *callback_baton, lldb::pid_t pid, bool monitor_signals)
 {
@@ -1458,30 +1460,20 @@ Host::StartMonitoringChildProcess(Host::MonitorChildProcessCallback callback, vo
     Log *log(lldb_private::GetLogIfAnyCategoriesSet (LIBLLDB_LOG_HOST | LIBLLDB_LOG_PROCESS));
 
 
-    dispatch_source_t source = ::dispatch_source_create (DISPATCH_SOURCE_TYPE_PROC, 
-                                                         pid, 
-                                                         mask, 
-                                                         ::dispatch_get_global_queue (DISPATCH_QUEUE_PRIORITY_DEFAULT,0));
-
     if (log)
-        log->Printf ("Host::StartMonitoringChildProcess (callback=%p, baton=%p, pid=%i, monitor_signals=%i) source = %p\n", 
+        log->Printf ("Host::StartMonitoringChildProcess (callback=%p, baton=%p, pid=%i, monitor_signals=%i)\n",
                      callback, 
                      callback_baton, 
                      (int)pid, 
-                     monitor_signals, 
-                     source);
-
-    if (source)
-    {
-        ::dispatch_source_set_cancel_handler (source, ^{
-            ::dispatch_release (source);
-        });
-        ::dispatch_source_set_event_handler (source, ^{
-            
-            int status= 0;
-            int wait_pid = 0;
-            bool cancel = false;
-            bool exited = false;
+                     monitor_signals);
+    
+    std::thread GrimReaper([callback, pid, log, callback_baton]() {
+        int status= 0;
+        int wait_pid = 0;
+        bool cancel = false;
+        bool exited = false;
+        while(!exited)
+        {
             do
             {
                 wait_pid = ::waitpid (pid, &status, 0);
@@ -1526,16 +1518,12 @@ Host::StartMonitoringChildProcess(Host::MonitorChildProcessCallback callback, vo
                 
                 if (callback)
                     cancel = callback (callback_baton, pid, exited, signal, exit_status);
-                
-                if (exited || cancel)
-                {
-                    ::dispatch_source_cancel(source);
-                }
             }
-        });
-
-        ::dispatch_resume (source);
-    }
+        }
+    });
+    
+    GrimReaper.detach();
+    
     return HostThread();
 }
 
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp
index d91fb7a443b..0952fec80fa 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp
@@ -11,7 +11,9 @@
 // C++ Includes
 // Other libraries and framework includes
 #include "clang/AST/ASTContext.h"
+#include "clang/AST/ASTDiagnostic.h"
 #include "clang/AST/ExternalASTSource.h"
+#include "clang/Basic/DiagnosticIDs.h"
 #include "clang/Basic/FileManager.h"
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Basic/TargetInfo.h"
@@ -64,20 +66,21 @@
 #include "lldb/Core/Module.h"
 #include "lldb/Core/Stream.h"
 #include "lldb/Core/StreamFile.h"
-#include "lldb/Core/StringList.h"
 #include "lldb/Core/StreamString.h"
-#include "lldb/Expression/IRExecutionUnit.h"
+#include "lldb/Core/StringList.h"
 #include "lldb/Expression/IRDynamicChecks.h"
+#include "lldb/Expression/IRExecutionUnit.h"
 #include "lldb/Expression/IRInterpreter.h"
 #include "lldb/Host/File.h"
 #include "lldb/Host/HostInfo.h"
 #include "lldb/Symbol/ClangASTContext.h"
 #include "lldb/Symbol/SymbolVendor.h"
 #include "lldb/Target/ExecutionContext.h"
+#include "lldb/Target/Language.h"
 #include "lldb/Target/ObjCLanguageRuntime.h"
 #include "lldb/Target/Process.h"
 #include "lldb/Target/Target.h"
-#include "lldb/Target/Language.h"
+#include "lldb/Utility/LLDBAssert.h"
 
 using namespace clang;
 using namespace llvm;
@@ -141,6 +144,76 @@ public:
     }
 };
 
+class ClangDiagnosticManagerAdapter : public clang::DiagnosticConsumer
+{
+public:
+    ClangDiagnosticManagerAdapter() : m_passthrough(new clang::TextDiagnosticBuffer) {}
+
+    ClangDiagnosticManagerAdapter(const std::shared_ptr<clang::TextDiagnosticBuffer> &passthrough)
+        : m_passthrough(passthrough)
+    {
+    }
+
+    void
+    ResetManager(DiagnosticManager *manager = nullptr)
+    {
+        m_manager = manager;
+    }
+
+    void
+    HandleDiagnostic(DiagnosticsEngine::Level DiagLevel, const clang::Diagnostic &Info)
+    {
+        if (m_manager)
+        {
+            llvm::SmallVector<char, 32> diag_str;
+            Info.FormatDiagnostic(diag_str);
+            diag_str.push_back('\0');
+            const char *data = diag_str.data();
+
+            switch (DiagLevel)
+            {
+                case DiagnosticsEngine::Level::Fatal:
+                case DiagnosticsEngine::Level::Error:
+                    m_manager->AddDiagnostic(data, eDiagnosticSeverityError, eDiagnosticOriginClang, Info.getID());
+                    break;
+                case DiagnosticsEngine::Level::Warning:
+                    m_manager->AddDiagnostic(data, eDiagnosticSeverityWarning, eDiagnosticOriginClang, Info.getID());
+                    break;
+                case DiagnosticsEngine::Level::Remark:
+                case DiagnosticsEngine::Level::Ignored:
+                    m_manager->AddDiagnostic(data, eDiagnosticSeverityRemark, eDiagnosticOriginClang, Info.getID());
+                    break;
+                case DiagnosticsEngine::Level::Note:
+                    m_manager->AppendMessageToDiagnostic(data);
+            }
+        }
+
+        m_passthrough->HandleDiagnostic(DiagLevel, Info);
+    }
+
+    void
+    FlushDiagnostics(DiagnosticsEngine &Diags)
+    {
+        m_passthrough->FlushDiagnostics(Diags);
+    }
+
+    DiagnosticConsumer *
+    clone(DiagnosticsEngine &Diags) const
+    {
+        return new ClangDiagnosticManagerAdapter(m_passthrough);
+    }
+
+    clang::TextDiagnosticBuffer *
+    GetPassthrough()
+    {
+        return m_passthrough.get();
+    }
+
+private:
+    DiagnosticManager *m_manager = nullptr;
+    std::shared_ptr<clang::TextDiagnosticBuffer> m_passthrough;
+};
+
 //===----------------------------------------------------------------------===//
 // Implementation of ClangExpressionParser
 //===----------------------------------------------------------------------===//
@@ -371,7 +444,7 @@ ClangExpressionParser::ClangExpressionParser (ExecutionContextScope *exe_scope,
 
     // 6. Set up the diagnostic buffer for reporting errors
 
-    m_compiler->getDiagnostics().setClient(new clang::TextDiagnosticBuffer);
+    m_compiler->getDiagnostics().setClient(new ClangDiagnosticManagerAdapter);
 
     // 7. Set up the source management objects inside the compiler
 
@@ -435,11 +508,15 @@ ClangExpressionParser::~ClangExpressionParser()
 }
 
 unsigned
-ClangExpressionParser::Parse(Stream &stream)
+ClangExpressionParser::Parse(DiagnosticManager &diagnostic_manager)
 {
-    TextDiagnosticBuffer *diag_buf = static_cast<TextDiagnosticBuffer *>(m_compiler->getDiagnostics().getClient());
+    ClangDiagnosticManagerAdapter *adapter =
+        static_cast<ClangDiagnosticManagerAdapter *>(m_compiler->getDiagnostics().getClient());
+    clang::TextDiagnosticBuffer *diag_buf = adapter->GetPassthrough();
     diag_buf->FlushDiagnostics(m_compiler->getDiagnostics());
 
+    adapter->ResetManager(&diagnostic_manager);
+
     const char *expr_text = m_expr.Text();
 
     clang::SourceManager &source_mgr = m_compiler->getSourceManager();
@@ -511,30 +588,21 @@ ClangExpressionParser::Parse(Stream &stream)
     if (m_pp_callbacks && m_pp_callbacks->hasErrors())
     {
         num_errors++;
-        stream.PutCString(m_pp_callbacks->getErrorString().c_str());
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "while importing modules:");
+        diagnostic_manager.AppendMessageToDiagnostic(m_pp_callbacks->getErrorString().c_str());
     }
 
-    for (TextDiagnosticBuffer::const_iterator warn = diag_buf->warn_begin(), warn_end = diag_buf->warn_end();
-         warn != warn_end; ++warn)
-        stream.Printf("warning: %s\n", warn->second.c_str());
-
-    for (TextDiagnosticBuffer::const_iterator err = diag_buf->err_begin(), err_end = diag_buf->err_end();
-         err != err_end; ++err)
-        stream.Printf("error: %s\n", err->second.c_str());
-
-    for (TextDiagnosticBuffer::const_iterator note = diag_buf->note_begin(), note_end = diag_buf->note_end();
-         note != note_end; ++note)
-        stream.Printf("note: %s\n", note->second.c_str());
-
     if (!num_errors)
     {
         if (type_system_helper->DeclMap() && !type_system_helper->DeclMap()->ResolveUnknownTypes())
         {
-            stream.Printf("error: Couldn't infer the type of a variable\n");
+            diagnostic_manager.Printf(eDiagnosticSeverityError, "Couldn't infer the type of a variable");
             num_errors++;
         }
     }
 
+    adapter->ResetManager();
+
     return num_errors;
 }
 
@@ -663,14 +731,14 @@ ClangExpressionParser::PrepareForExecution (lldb::addr_t &func_addr,
                 {
                     DynamicCheckerFunctions *dynamic_checkers = new DynamicCheckerFunctions();
 
-                    StreamString install_errors;
+                    DiagnosticManager install_diagnostics;
 
-                    if (!dynamic_checkers->Install(install_errors, exe_ctx))
+                    if (!dynamic_checkers->Install(install_diagnostics, exe_ctx))
                     {
-                        if (install_errors.GetString().empty())
-                            err.SetErrorString ("couldn't install checkers, unknown error");
+                        if (install_diagnostics.Diagnostics().size())
+                            err.SetErrorString("couldn't install checkers, unknown error");
                         else
-                            err.SetErrorString (install_errors.GetString().c_str());
+                            err.SetErrorString(install_diagnostics.GetString().c_str());
 
                         return err;
                     }
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.h b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.h
index 3c055380b83..832dce7ec57 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.h
@@ -10,11 +10,12 @@
 #ifndef liblldb_ClangExpressionParser_h_
 #define liblldb_ClangExpressionParser_h_
 
-#include "lldb/lldb-public.h"
 #include "lldb/Core/ArchSpec.h"
 #include "lldb/Core/ClangForward.h"
 #include "lldb/Core/Error.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/ExpressionParser.h"
+#include "lldb/lldb-public.h"
 
 #include <string>
 #include <vector>
@@ -63,16 +64,16 @@ public:
     /// Parse a single expression and convert it to IR using Clang.  Don't
     /// wrap the expression in anything at all.
     ///
-    /// @param[in] stream
-    ///     The stream to print errors to.
+    /// @param[in] diagnostic_manager
+    ///     The diagnostic manager to report errors to.
     ///
     /// @return
     ///     The number of errors encountered during parsing.  0 means
     ///     success.
     //------------------------------------------------------------------
     unsigned
-    Parse (Stream &stream) override;
-    
+    Parse(DiagnosticManager &diagnostic_manager) override;
+
     //------------------------------------------------------------------
     /// Ready an already-parsed expression for execution, possibly
     /// evaluating it statically.
@@ -98,7 +99,7 @@ public:
     ///
     /// @param[out] const_result
     ///     If the result of the expression is constant, and the
-    ///     expression has no side effects, this is set to the result of the 
+    ///     expression has no side effects, this is set to the result of the
     ///     expression.
     ///
     /// @param[in] execution_policy
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.cpp
index 0d0d7475a00..a82394592c4 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.cpp
@@ -74,11 +74,11 @@ ClangFunctionCaller::~ClangFunctionCaller()
 }
 
 unsigned
-ClangFunctionCaller::CompileFunction (Stream &errors)
+ClangFunctionCaller::CompileFunction(DiagnosticManager &diagnostic_manager)
 {
     if (m_compiled)
         return 0;
-    
+
     // FIXME: How does clang tell us there's no return value?  We need to handle that case.
     unsigned num_errors = 0;
     
@@ -143,8 +143,9 @@ ClangFunctionCaller::CompileFunction (Stream &errors)
                 type_name = clang_qual_type.GetTypeName().AsCString("");
             }
             else
-            {   
-                errors.Printf("Could not determine type of input value %" PRIu64 ".", (uint64_t)i);
+            {
+                diagnostic_manager.Printf(eDiagnosticSeverityError,
+                                          "Could not determine type of input value %" PRIu64 ".", (uint64_t)i);
                 return 1;
             }
         }
@@ -195,15 +196,15 @@ ClangFunctionCaller::CompileFunction (Stream &errors)
     {
         const bool generate_debug_info = true;
         m_parser.reset(new ClangExpressionParser(jit_process_sp.get(), *this, generate_debug_info));
-        
-        num_errors = m_parser->Parse (errors);
+
+        num_errors = m_parser->Parse(diagnostic_manager);
     }
     else
     {
-        errors.Printf("no process - unable to inject function");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "no process - unable to inject function");
         num_errors = 1;
     }
-    
+
     m_compiled = (num_errors == 0);
     
     if (!m_compiled)
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.h b/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.h
index 3e30f818a93..f37c3b30472 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.h
@@ -137,17 +137,17 @@ public:
     //------------------------------------------------------------------
     /// Compile the wrapper function
     ///
-    /// @param[in] errors
-    ///     The stream to print parser errors to.
+    /// @param[in] diagnostic_manager
+    ///     The diagnostic manager to report parser errors to.
     ///
     /// @return
     ///     The number of errors.
     //------------------------------------------------------------------
     unsigned
-    CompileFunction (Stream &errors) override;
-    
+    CompileFunction(DiagnosticManager &diagnostic_manager) override;
+
     ExpressionTypeSystemHelper *
-    GetTypeSystemHelper () override
+    GetTypeSystemHelper() override
     {
         return &m_type_system_helper;
     }
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp
index 11f7f84ff5f..25ac0e21711 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp
@@ -326,11 +326,9 @@ ApplyObjcCastHack(std::string &expr)
 }
 
 bool
-ClangUserExpression::Parse (Stream &error_stream,
-                            ExecutionContext &exe_ctx,
-                            lldb_private::ExecutionPolicy execution_policy,
-                            bool keep_result_in_memory,
-                            bool generate_debug_info)
+ClangUserExpression::Parse(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+                           lldb_private::ExecutionPolicy execution_policy, bool keep_result_in_memory,
+                           bool generate_debug_info)
 {
     Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS));
 
@@ -346,13 +344,13 @@ ClangUserExpression::Parse (Stream &error_stream,
         }
         else
         {
-            error_stream.PutCString ("error: couldn't start parsing (no persistent data)");
+            diagnostic_manager.PutCString(eDiagnosticSeverityError, "couldn't start parsing (no persistent data)");
             return false;
         }
     }
     else
     {
-        error_stream.PutCString ("error: couldn't start parsing (no target)");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "error: couldn't start parsing (no target)");
         return false;
     }
 
@@ -360,7 +358,7 @@ ClangUserExpression::Parse (Stream &error_stream,
 
     if (!err.Success())
     {
-        error_stream.Printf("warning: %s\n", err.AsCString());
+        diagnostic_manager.PutCString(eDiagnosticSeverityWarning, err.AsCString());
     }
 
     StreamString m_transformed_stream;
@@ -418,7 +416,7 @@ ClangUserExpression::Parse (Stream &error_stream,
 
     if (!source_code->GetText(m_transformed_text, lang_type, m_const_object, m_in_static_method, exe_ctx))
     {
-        error_stream.PutCString ("error: couldn't construct expression body");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "couldn't construct expression body");
         return false;
     }
 
@@ -433,7 +431,7 @@ ClangUserExpression::Parse (Stream &error_stream,
 
     if (!target)
     {
-        error_stream.PutCString ("error: invalid target\n");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "invalid target");
         return false;
     }
 
@@ -467,7 +465,8 @@ ClangUserExpression::Parse (Stream &error_stream,
 
     if (!DeclMap()->WillParse(exe_ctx, m_materializer_ap.get()))
     {
-        error_stream.PutCString ("error: current process state is unsuitable for expression parsing\n");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError,
+                                      "current process state is unsuitable for expression parsing");
 
         ResetDeclMap(); // We are being careful here in the case of breakpoint conditions.
 
@@ -482,11 +481,12 @@ ClangUserExpression::Parse (Stream &error_stream,
 
     ClangExpressionParser parser(exe_scope, *this, generate_debug_info);
 
-    unsigned num_errors = parser.Parse (error_stream);
+    unsigned num_errors = parser.Parse(diagnostic_manager);
 
     if (num_errors)
     {
-        error_stream.Printf ("error: %d errors parsing expression\n", num_errors);
+        diagnostic_manager.Printf(eDiagnosticSeverityError, "%u error%s parsing expression", num_errors,
+                                  num_errors == 1 ? "" : "s");
 
         ResetDeclMap(); // We are being careful here in the case of breakpoint conditions.
 
@@ -547,22 +547,20 @@ ClangUserExpression::Parse (Stream &error_stream,
     {
         const char *error_cstr = jit_error.AsCString();
         if (error_cstr && error_cstr[0])
-            error_stream.Printf ("error: %s\n", error_cstr);
+            diagnostic_manager.PutCString(eDiagnosticSeverityError, error_cstr);
         else
-            error_stream.Printf ("error: expression can't be interpreted or run\n");
+            diagnostic_manager.Printf(eDiagnosticSeverityError, "expression can't be interpreted or run");
         return false;
     }
 }
 
 bool
-ClangUserExpression::AddArguments (ExecutionContext &exe_ctx,
-                                   std::vector<lldb::addr_t> &args,
-                                   lldb::addr_t struct_address,
-                                   Stream &error_stream)
+ClangUserExpression::AddArguments(ExecutionContext &exe_ctx, std::vector<lldb::addr_t> &args,
+                                  lldb::addr_t struct_address, DiagnosticManager &diagnostic_manager)
 {
     lldb::addr_t object_ptr = LLDB_INVALID_ADDRESS;
-    lldb::addr_t cmd_ptr    = LLDB_INVALID_ADDRESS;
-    
+    lldb::addr_t cmd_ptr = LLDB_INVALID_ADDRESS;
+
     if (m_needs_object_ptr)
     {
         lldb::StackFrameSP frame_sp = exe_ctx.GetFrameSP();
@@ -581,7 +579,7 @@ ClangUserExpression::AddArguments (ExecutionContext &exe_ctx,
         }
         else
         {
-            error_stream.Printf("Need object pointer but don't know the language\n");
+            diagnostic_manager.PutCString(eDiagnosticSeverityError, "need object pointer but don't know the language");
             return false;
         }
 
@@ -591,7 +589,9 @@ ClangUserExpression::AddArguments (ExecutionContext &exe_ctx,
 
         if (!object_ptr_error.Success())
         {
-            error_stream.Printf("warning: couldn't get required object pointer (substituting NULL): %s\n", object_ptr_error.AsCString());
+            diagnostic_manager.Printf(eDiagnosticSeverityWarning,
+                                      "couldn't get required object pointer (substituting NULL): %s",
+                                      object_ptr_error.AsCString());
             object_ptr = 0;
         }
 
@@ -603,7 +603,9 @@ ClangUserExpression::AddArguments (ExecutionContext &exe_ctx,
 
             if (!object_ptr_error.Success())
             {
-                error_stream.Printf("warning: couldn't get cmd pointer (substituting NULL): %s\n", object_ptr_error.AsCString());
+                diagnostic_manager.Printf(eDiagnosticSeverityWarning,
+                                          "couldn't get cmd pointer (substituting NULL): %s",
+                                          object_ptr_error.AsCString());
                 cmd_ptr = 0;
             }
         }
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.h b/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.h
index f2bfe31dce0..3177da358af 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.h
@@ -126,8 +126,8 @@ public:
     //------------------------------------------------------------------
     /// Parse the expression
     ///
-    /// @param[in] error_stream
-    ///     A stream to print parse errors and warnings to.
+    /// @param[in] diagnostic_manager
+    ///     A diagnostic manager to report parse errors and warnings to.
     ///
     /// @param[in] exe_ctx
     ///     The execution context to use when looking up entities that
@@ -145,11 +145,9 @@ public:
     ///     True on success (no errors); false otherwise.
     //------------------------------------------------------------------
     bool
-    Parse (Stream &error_stream,
-           ExecutionContext &exe_ctx,
-           lldb_private::ExecutionPolicy execution_policy,
-           bool keep_result_in_memory,
-           bool generate_debug_info) override;
+    Parse(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+          lldb_private::ExecutionPolicy execution_policy, bool keep_result_in_memory,
+          bool generate_debug_info) override;
 
     ExpressionTypeSystemHelper *
     GetTypeSystemHelper () override
@@ -188,13 +186,11 @@ private:
                  lldb_private::Error &err) override;
 
     bool
-    AddArguments (ExecutionContext &exe_ctx,
-                  std::vector<lldb::addr_t> &args,
-                  lldb::addr_t struct_address,
-                  Stream &error_stream) override;
-    
-    ClangUserExpressionHelper   m_type_system_helper;
-    
+    AddArguments(ExecutionContext &exe_ctx, std::vector<lldb::addr_t> &args, lldb::addr_t struct_address,
+                 DiagnosticManager &diagnostic_manager) override;
+
+    ClangUserExpressionHelper m_type_system_helper;
+
     class ResultDelegate : public Materializer::PersistentVariableDelegate
     {
     public:
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.cpp
index fe044c17ac7..2a11be679fd 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.cpp
@@ -55,8 +55,8 @@ ClangUtilityFunction::~ClangUtilityFunction ()
 //------------------------------------------------------------------
 /// Install the utility function into a process
 ///
-/// @param[in] error_stream
-///     A stream to print parse errors and warnings to.
+/// @param[in] diagnostic_manager
+///     A diagnostic manager to report errors and warnings to.
 ///
 /// @param[in] exe_ctx
 ///     The execution context to install the utility function to.
@@ -65,35 +65,34 @@ ClangUtilityFunction::~ClangUtilityFunction ()
 ///     True on success (no errors); false otherwise.
 //------------------------------------------------------------------
 bool
-ClangUtilityFunction::Install (Stream &error_stream,
-                               ExecutionContext &exe_ctx)
+ClangUtilityFunction::Install(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx)
 {
     if (m_jit_start_addr != LLDB_INVALID_ADDRESS)
     {
-        error_stream.PutCString("error: already installed\n");
+        diagnostic_manager.PutCString(eDiagnosticSeverityWarning, "already installed");
         return false;
     }
-    
+
     ////////////////////////////////////
     // Set up the target and compiler
     //
     
     Target *target = exe_ctx.GetTargetPtr();
-    
+
     if (!target)
     {
-        error_stream.PutCString ("error: invalid target\n");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "invalid target");
         return false;
     }
-    
+
     Process *process = exe_ctx.GetProcessPtr();
-    
+
     if (!process)
     {
-        error_stream.PutCString ("error: invalid process\n");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "invalid process");
         return false;
     }
-        
+
     //////////////////////////
     // Parse the expression
     //
@@ -101,24 +100,26 @@ ClangUtilityFunction::Install (Stream &error_stream,
     bool keep_result_in_memory = false;
     
     ResetDeclMap(exe_ctx, keep_result_in_memory);
-    
+
     if (!DeclMap()->WillParse(exe_ctx, NULL))
     {
-        error_stream.PutCString ("error: current process state is unsuitable for expression parsing\n");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError,
+                                      "current process state is unsuitable for expression parsing");
         return false;
     }
-    
+
     const bool generate_debug_info = true;
     ClangExpressionParser parser(exe_ctx.GetBestExecutionContextScope(), *this, generate_debug_info);
-    
-    unsigned num_errors = parser.Parse (error_stream);
-    
+
+    unsigned num_errors = parser.Parse(diagnostic_manager);
+
     if (num_errors)
     {
-        error_stream.Printf ("error: %d errors parsing expression\n", num_errors);
-        
+        diagnostic_manager.Printf(eDiagnosticSeverityError, "%d error%s parsing expression", num_errors,
+                                  num_errors == 1 ? "" : "s");
+
         ResetDeclMap();
-        
+
         return false;
     }
     
@@ -175,9 +176,13 @@ ClangUtilityFunction::Install (Stream &error_stream,
     {
         const char *error_cstr = jit_error.AsCString();
         if (error_cstr && error_cstr[0])
-            error_stream.Printf ("error: %s\n", error_cstr);
+        {
+            diagnostic_manager.Printf(eDiagnosticSeverityError, "%s", error_cstr);
+        }
         else
-            error_stream.Printf ("error: expression can't be interpreted or run\n");
+        {
+            diagnostic_manager.PutCString(eDiagnosticSeverityError, "expression can't be interpreted or run");
+        }
         return false;
     }
 }
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.h b/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.h
index 74839717946..d4ed37eee04 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.h
@@ -124,12 +124,12 @@ public:
     {
         m_type_system_helper.ResetDeclMap(exe_ctx, keep_result_in_memory);
     }
-    
+
     bool
-    Install (Stream &error_stream, ExecutionContext &exe_ctx) override;
-    
+    Install(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx) override;
+
 private:
-    ClangUtilityFunctionHelper  m_type_system_helper;    ///< The map to use when parsing and materializing the expression.
+    ClangUtilityFunctionHelper m_type_system_helper; ///< The map to use when parsing and materializing the expression.
 };
 
 } // namespace lldb_private
diff --git a/lldb/source/Plugins/ExpressionParser/Go/GoUserExpression.cpp b/lldb/source/Plugins/ExpressionParser/Go/GoUserExpression.cpp
index 0b074f87c16..0457bfe0f32 100644
--- a/lldb/source/Plugins/ExpressionParser/Go/GoUserExpression.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Go/GoUserExpression.cpp
@@ -26,7 +26,6 @@
 // Project includes
 #include "GoUserExpression.h"
 
-#include "lldb/lldb-private.h"
 #include "lldb/Core/ConstString.h"
 #include "lldb/Core/DataBufferHeap.h"
 #include "lldb/Core/DataEncoder.h"
@@ -37,10 +36,11 @@
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/ValueObjectConstResult.h"
 #include "lldb/Core/ValueObjectRegister.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/ExpressionVariable.h"
-#include "lldb/Symbol/TypeList.h"
 #include "lldb/Symbol/GoASTContext.h"
 #include "lldb/Symbol/SymbolFile.h"
+#include "lldb/Symbol/TypeList.h"
 #include "lldb/Symbol/VariableList.h"
 #include "lldb/Target/ExecutionContext.h"
 #include "lldb/Target/Process.h"
@@ -49,6 +49,7 @@
 #include "lldb/Target/Target.h"
 #include "lldb/Target/ThreadPlan.h"
 #include "lldb/Target/ThreadPlanCallUserExpression.h"
+#include "lldb/lldb-private.h"
 
 #include "Plugins/ExpressionParser/Go/GoAST.h"
 #include "Plugins/ExpressionParser/Go/GoParser.h"
@@ -247,8 +248,9 @@ GoUserExpression::GoUserExpression(ExecutionContextScope &exe_scope, const char
 }
 
 bool
-GoUserExpression::Parse(Stream &error_stream, ExecutionContext &exe_ctx, lldb_private::ExecutionPolicy execution_policy,
-                        bool keep_result_in_memory, bool generate_debug_info)
+GoUserExpression::Parse(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+                        lldb_private::ExecutionPolicy execution_policy, bool keep_result_in_memory,
+                        bool generate_debug_info)
 {
     InstallContext(exe_ctx);
     m_interpreter.reset(new GoInterpreter(exe_ctx, GetUserText()));
@@ -256,15 +258,16 @@ GoUserExpression::Parse(Stream &error_stream, ExecutionContext &exe_ctx, lldb_pr
         return true;
     const char *error_cstr = m_interpreter->error().AsCString();
     if (error_cstr && error_cstr[0])
-        error_stream.Printf("error: %s\n", error_cstr);
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, error_cstr);
     else
-        error_stream.Printf("error: expression can't be interpreted or run\n");
+        diagnostic_manager.Printf(eDiagnosticSeverityError, "expression can't be interpreted or run");
     return false;
 }
 
 lldb::ExpressionResults
-GoUserExpression::Execute(Stream &error_stream, ExecutionContext &exe_ctx, const EvaluateExpressionOptions &options,
-                          lldb::UserExpressionSP &shared_ptr_to_me, lldb::ExpressionVariableSP &result)
+GoUserExpression::Execute(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+                          const EvaluateExpressionOptions &options, lldb::UserExpressionSP &shared_ptr_to_me,
+                          lldb::ExpressionVariableSP &result)
 {
     Log *log(lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_EXPRESSIONS | LIBLLDB_LOG_STEP));
 
@@ -281,7 +284,7 @@ GoUserExpression::Execute(Stream &error_stream, ExecutionContext &exe_ctx, const
             if (log)
                 log->Printf("== [GoUserExpression::Evaluate] Expression may not run, but is not constant ==");
 
-            error_stream.Printf("expression needed to run but couldn't");
+            diagnostic_manager.PutCString(eDiagnosticSeverityError, "expression needed to run but couldn't");
 
             return execution_results;
         }
@@ -296,9 +299,9 @@ GoUserExpression::Execute(Stream &error_stream, ExecutionContext &exe_ctx, const
     {
         const char *error_cstr = err.AsCString();
         if (error_cstr && error_cstr[0])
-            error_stream.Printf("error: %s\n", error_cstr);
+            diagnostic_manager.PutCString(eDiagnosticSeverityError, error_cstr);
         else
-            error_stream.Printf("error: expression can't be interpreted or run\n");
+            diagnostic_manager.PutCString(eDiagnosticSeverityError, "expression can't be interpreted or run");
         return lldb::eExpressionDiscarded;
     }
     result.reset(new ExpressionVariable(ExpressionVariable::eKindGo));
diff --git a/lldb/source/Plugins/ExpressionParser/Go/GoUserExpression.h b/lldb/source/Plugins/ExpressionParser/Go/GoUserExpression.h
index b429c68f023..4d6cdd2fcd1 100644
--- a/lldb/source/Plugins/ExpressionParser/Go/GoUserExpression.h
+++ b/lldb/source/Plugins/ExpressionParser/Go/GoUserExpression.h
@@ -62,30 +62,31 @@ class GoPersistentExpressionState : public PersistentExpressionState
 class GoUserExpression : public UserExpression
 {
   public:
-    GoUserExpression(ExecutionContextScope &exe_scope, const char *expr, const char *expr_prefix,
-                     lldb::LanguageType language, ResultType desired_type, const EvaluateExpressionOptions &options);
-
-    bool
-    Parse(Stream &error_stream, ExecutionContext &exe_ctx, lldb_private::ExecutionPolicy execution_policy,
-          bool keep_result_in_memory, bool generate_debug_info) override;
-
-    lldb::ExpressionResults
-    Execute(Stream &error_stream, ExecutionContext &exe_ctx,
-            const EvaluateExpressionOptions &options,
-            lldb::UserExpressionSP &shared_ptr_to_me,
-            lldb::ExpressionVariableSP &result) override;
-
-    bool
-    CanInterpret() override
-    {
-        return true;
-    }
-    bool
-    FinalizeJITExecution(Stream &error_stream, ExecutionContext &exe_ctx, lldb::ExpressionVariableSP &result,
-                         lldb::addr_t function_stack_bottom = LLDB_INVALID_ADDRESS,
-                         lldb::addr_t function_stack_top = LLDB_INVALID_ADDRESS) override
-    {
-        return true;
+      GoUserExpression(ExecutionContextScope &exe_scope, const char *expr, const char *expr_prefix,
+                       lldb::LanguageType language, ResultType desired_type, const EvaluateExpressionOptions &options);
+
+      bool
+      Parse(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+            lldb_private::ExecutionPolicy execution_policy, bool keep_result_in_memory,
+            bool generate_debug_info) override;
+
+      lldb::ExpressionResults
+      Execute(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+              const EvaluateExpressionOptions &options, lldb::UserExpressionSP &shared_ptr_to_me,
+              lldb::ExpressionVariableSP &result) override;
+
+      bool
+      CanInterpret() override
+      {
+          return true;
+      }
+      bool
+      FinalizeJITExecution(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+                           lldb::ExpressionVariableSP &result,
+                           lldb::addr_t function_stack_bottom = LLDB_INVALID_ADDRESS,
+                           lldb::addr_t function_stack_top = LLDB_INVALID_ADDRESS) override
+      {
+          return true;
     }
 
   private:
diff --git a/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntime.cpp b/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntime.cpp
index 2810b24cb7a..9430e38f694 100644
--- a/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntime.cpp
+++ b/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntime.cpp
@@ -23,6 +23,7 @@
 #include "lldb/Core/Section.h"
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/ValueObject.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/FunctionCaller.h"
 #include "lldb/Symbol/ClangASTContext.h"
 #include "lldb/Symbol/ObjectFile.h"
@@ -151,10 +152,10 @@ AppleObjCRuntime::GetObjectDescription (Stream &strm, Value &value, ExecutionCon
             exe_ctx.SetFrameSP(thread->GetSelectedFrame());
         }
     }
-    
+
     // Now we're ready to call the function:
-    
-    StreamString error_stream;
+
+    DiagnosticManager diagnostics;
     lldb::addr_t wrapper_struct_addr = LLDB_INVALID_ADDRESS;
 
     if (!m_print_object_caller_up)
@@ -172,30 +173,22 @@ AppleObjCRuntime::GetObjectDescription (Stream &strm, Value &value, ExecutionCon
             strm.Printf("Could not get function runner to call print for debugger function: %s.", error.AsCString());
             return false;
         }
-        m_print_object_caller_up->InsertFunction(exe_ctx, wrapper_struct_addr, error_stream);
+        m_print_object_caller_up->InsertFunction(exe_ctx, wrapper_struct_addr, diagnostics);
     }
     else
     {
-        m_print_object_caller_up->WriteFunctionArguments(exe_ctx,
-                                                         wrapper_struct_addr,
-                                                         arg_value_list,
-                                                         error_stream);
+        m_print_object_caller_up->WriteFunctionArguments(exe_ctx, wrapper_struct_addr, arg_value_list, diagnostics);
     }
 
-    
-
     EvaluateExpressionOptions options;
     options.SetUnwindOnError(true);
     options.SetTryAllThreads(true);
     options.SetStopOthers(true);
     options.SetIgnoreBreakpoints(true);
     options.SetTimeoutUsec(PO_FUNCTION_TIMEOUT_USEC);
-    
-    ExpressionResults results = m_print_object_caller_up->ExecuteFunction (exe_ctx,
-                                                                           &wrapper_struct_addr,
-                                                                           options,
-                                                                           error_stream,
-                                                                           ret);
+
+    ExpressionResults results =
+        m_print_object_caller_up->ExecuteFunction(exe_ctx, &wrapper_struct_addr, options, diagnostics, ret);
     if (results != eExpressionCompleted)
     {
         strm.Printf("Error evaluating Print Object function: %d.\n", results);
diff --git a/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntimeV2.cpp b/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntimeV2.cpp
index 430fbaed54d..638b651d513 100644
--- a/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntimeV2.cpp
+++ b/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntimeV2.cpp
@@ -36,6 +36,7 @@
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/Timer.h"
 #include "lldb/Core/ValueObjectVariable.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/FunctionCaller.h"
 #include "lldb/Expression/UtilityFunction.h"
 #include "lldb/Host/StringConvert.h"
@@ -1239,13 +1240,13 @@ AppleObjCRuntimeV2::UpdateISAToDescriptorMapDynamic(RemoteNXMapTable &hash_table
     
     if (!ast)
         return false;
-    
+
     Address function_address;
-    
-    StreamString errors;
-    
+
+    DiagnosticManager diagnostics;
+
     const uint32_t addr_size = process->GetAddressByteSize();
-    
+
     Error err;
     
     // Read the total number of classes from the hash table
@@ -1279,12 +1280,15 @@ AppleObjCRuntimeV2::UpdateISAToDescriptorMapDynamic(RemoteNXMapTable &hash_table
         }
         else
         {
-            errors.Clear();
-            
-            if (!m_get_class_info_code->Install(errors, exe_ctx))
+            diagnostics.Clear();
+
+            if (!m_get_class_info_code->Install(diagnostics, exe_ctx))
             {
                 if (log)
-                    log->Printf ("Failed to install implementation lookup: %s.", errors.GetData());
+                {
+                    log->Printf("Failed to install implementation lookup");
+                    diagnostics.Dump(log);
+                }
                 m_get_class_info_code.reset();
             }
         }
@@ -1319,14 +1323,18 @@ AppleObjCRuntimeV2::UpdateISAToDescriptorMapDynamic(RemoteNXMapTable &hash_table
         if (!get_class_info_function)
         {
             if (log)
-                log->Printf ("Failed to get implementation lookup function caller: %s.", errors.GetData());
+            {
+                log->Printf("Failed to get implementation lookup function caller.");
+                diagnostics.Dump(log);
+            }
+
             return false;
         }
         arguments = get_class_info_function->GetArgumentValues();
     }
 
-    errors.Clear();
-    
+    diagnostics.Clear();
+
     const uint32_t class_info_byte_size = addr_size + 4;
     const uint32_t class_infos_byte_size = num_classes * class_info_byte_size;
     lldb::addr_t class_infos_addr = process->AllocateMemory(class_infos_byte_size,
@@ -1342,16 +1350,13 @@ AppleObjCRuntimeV2::UpdateISAToDescriptorMapDynamic(RemoteNXMapTable &hash_table
     arguments.GetValueAtIndex(0)->GetScalar() = hash_table.GetTableLoadAddress();
     arguments.GetValueAtIndex(1)->GetScalar() = class_infos_addr;
     arguments.GetValueAtIndex(2)->GetScalar() = class_infos_byte_size;
-    
+
     bool success = false;
-    
-    errors.Clear();
-    
+
+    diagnostics.Clear();
+
     // Write our function arguments into the process so we can run our function
-    if (get_class_info_function->WriteFunctionArguments (exe_ctx,
-                                                           m_get_class_info_args,
-                                                           arguments,
-                                                           errors))
+    if (get_class_info_function->WriteFunctionArguments(exe_ctx, m_get_class_info_args, arguments, diagnostics))
     {
         EvaluateExpressionOptions options;
         options.SetUnwindOnError(true);
@@ -1363,18 +1368,15 @@ AppleObjCRuntimeV2::UpdateISAToDescriptorMapDynamic(RemoteNXMapTable &hash_table
         Value return_value;
         return_value.SetValueType (Value::eValueTypeScalar);
         //return_value.SetContext (Value::eContextTypeClangType, clang_uint32_t_type);
-        return_value.SetCompilerType (clang_uint32_t_type);
+        return_value.SetCompilerType(clang_uint32_t_type);
         return_value.GetScalar() = 0;
-        
-        errors.Clear();
-        
+
+        diagnostics.Clear();
+
         // Run the function
-        ExpressionResults results = get_class_info_function->ExecuteFunction (exe_ctx,
-                                                                              &m_get_class_info_args,
-                                                                              options,
-                                                                              errors,
-                                                                              return_value);
-        
+        ExpressionResults results = get_class_info_function->ExecuteFunction(exe_ctx, &m_get_class_info_args, options,
+                                                                             diagnostics, return_value);
+
         if (results == eExpressionCompleted)
         {
             // The result is the number of ClassInfo structures that were filled in
@@ -1399,15 +1401,21 @@ AppleObjCRuntimeV2::UpdateISAToDescriptorMapDynamic(RemoteNXMapTable &hash_table
         else
         {
             if (log)
-                log->Printf("Error evaluating our find class name function: %s.\n", errors.GetData());
+            {
+                log->Printf("Error evaluating our find class name function.");
+                diagnostics.Dump(log);
+            }
         }
     }
     else
     {
         if (log)
-            log->Printf ("Error writing function arguments: \"%s\".", errors.GetData());
+        {
+            log->Printf("Error writing function arguments.");
+            diagnostics.Dump(log);
+        }
     }
-    
+
     // Deallocate the memory we allocated for the ClassInfo array
     process->DeallocateMemory(class_infos_addr);
     
@@ -1483,13 +1491,13 @@ AppleObjCRuntimeV2::UpdateISAToDescriptorMapSharedCache()
     
     if (!ast)
         return DescriptorMapUpdateResult::Fail();
-    
+
     Address function_address;
-    
-    StreamString errors;
-    
+
+    DiagnosticManager diagnostics;
+
     const uint32_t addr_size = process->GetAddressByteSize();
-    
+
     Error err;
     
     const lldb::addr_t objc_opt_ptr = GetSharedCacheReadOnlyAddress();
@@ -1528,16 +1536,19 @@ AppleObjCRuntimeV2::UpdateISAToDescriptorMapSharedCache()
         }
         else
         {
-            errors.Clear();
-            
-            if (!m_get_shared_cache_class_info_code->Install(errors, exe_ctx))
+            diagnostics.Clear();
+
+            if (!m_get_shared_cache_class_info_code->Install(diagnostics, exe_ctx))
             {
                 if (log)
-                    log->Printf ("Failed to install implementation lookup: %s.", errors.GetData());
+                {
+                    log->Printf("Failed to install implementation lookup.");
+                    diagnostics.Dump(log);
+                }
                 m_get_shared_cache_class_info_code.reset();
             }
         }
-        
+
         if (!m_get_shared_cache_class_info_code.get())
             return DescriptorMapUpdateResult::Fail();
     
@@ -1569,9 +1580,9 @@ AppleObjCRuntimeV2::UpdateISAToDescriptorMapSharedCache()
             return DescriptorMapUpdateResult::Fail();
         arguments = get_shared_cache_class_info_function->GetArgumentValues();
     }
-    
-    errors.Clear();
-    
+
+    diagnostics.Clear();
+
     const uint32_t class_info_byte_size = addr_size + 4;
     const uint32_t class_infos_byte_size = num_classes * class_info_byte_size;
     lldb::addr_t class_infos_addr = process->AllocateMemory (class_infos_byte_size,
@@ -1587,17 +1598,15 @@ AppleObjCRuntimeV2::UpdateISAToDescriptorMapSharedCache()
     arguments.GetValueAtIndex(0)->GetScalar() = objc_opt_ptr;
     arguments.GetValueAtIndex(1)->GetScalar() = class_infos_addr;
     arguments.GetValueAtIndex(2)->GetScalar() = class_infos_byte_size;
-    
+
     bool success = false;
     bool any_found = false;
-    
-    errors.Clear();
-    
+
+    diagnostics.Clear();
+
     // Write our function arguments into the process so we can run our function
-    if (get_shared_cache_class_info_function->WriteFunctionArguments (exe_ctx,
-                                                                      m_get_shared_cache_class_info_args,
-                                                                      arguments,
-                                                                      errors))
+    if (get_shared_cache_class_info_function->WriteFunctionArguments(exe_ctx, m_get_shared_cache_class_info_args,
+                                                                     arguments, diagnostics))
     {
         EvaluateExpressionOptions options;
         options.SetUnwindOnError(true);
@@ -1609,18 +1618,15 @@ AppleObjCRuntimeV2::UpdateISAToDescriptorMapSharedCache()
         Value return_value;
         return_value.SetValueType (Value::eValueTypeScalar);
         //return_value.SetContext (Value::eContextTypeClangType, clang_uint32_t_type);
-        return_value.SetCompilerType (clang_uint32_t_type);
+        return_value.SetCompilerType(clang_uint32_t_type);
         return_value.GetScalar() = 0;
-        
-        errors.Clear();
-        
+
+        diagnostics.Clear();
+
         // Run the function
-        ExpressionResults results = get_shared_cache_class_info_function->ExecuteFunction (exe_ctx,
-                                                                                           &m_get_shared_cache_class_info_args,
-                                                                                           options,
-                                                                                           errors,
-                                                                                           return_value);
-        
+        ExpressionResults results = get_shared_cache_class_info_function->ExecuteFunction(
+            exe_ctx, &m_get_shared_cache_class_info_args, options, diagnostics, return_value);
+
         if (results == eExpressionCompleted)
         {
             // The result is the number of ClassInfo structures that were filled in
@@ -1666,15 +1672,21 @@ AppleObjCRuntimeV2::UpdateISAToDescriptorMapSharedCache()
         else
         {
             if (log)
-                log->Printf("Error evaluating our find class name function: %s.\n", errors.GetData());
+            {
+                log->Printf("Error evaluating our find class name function.");
+                diagnostics.Dump(log);
+            }
         }
     }
     else
     {
         if (log)
-            log->Printf ("Error writing function arguments: \"%s\".", errors.GetData());
+        {
+            log->Printf("Error writing function arguments.");
+            diagnostics.Dump(log);
+        }
     }
-    
+
     // Deallocate the memory we allocated for the ClassInfo array
     process->DeallocateMemory(class_infos_addr);
     
diff --git a/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCTrampolineHandler.cpp b/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCTrampolineHandler.cpp
index d38a076ad5d..b9994d63952 100644
--- a/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCTrampolineHandler.cpp
+++ b/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCTrampolineHandler.cpp
@@ -22,19 +22,20 @@
 #include "lldb/Core/Module.h"
 #include "lldb/Core/StreamFile.h"
 #include "lldb/Core/Value.h"
-#include "lldb/Expression/UserExpression.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/FunctionCaller.h"
+#include "lldb/Expression/UserExpression.h"
 #include "lldb/Expression/UtilityFunction.h"
 #include "lldb/Host/FileSpec.h"
 #include "lldb/Symbol/ClangASTContext.h"
 #include "lldb/Symbol/Symbol.h"
 #include "lldb/Target/ABI.h"
+#include "lldb/Target/ExecutionContext.h"
 #include "lldb/Target/ObjCLanguageRuntime.h"
 #include "lldb/Target/Process.h"
 #include "lldb/Target/RegisterContext.h"
 #include "lldb/Target/Target.h"
 #include "lldb/Target/Thread.h"
-#include "lldb/Target/ExecutionContext.h"
 #include "lldb/Target/ThreadPlanRunToAddress.h"
 
 #include "llvm/ADT/STLExtras.h"
@@ -738,11 +739,11 @@ AppleObjCTrampolineHandler::AppleObjCTrampolineHandler (const ProcessSP &process
 }
 
 lldb::addr_t
-AppleObjCTrampolineHandler::SetupDispatchFunction (Thread &thread, ValueList &dispatch_values)
+AppleObjCTrampolineHandler::SetupDispatchFunction(Thread &thread, ValueList &dispatch_values)
 {
-    ExecutionContext exe_ctx (thread.shared_from_this());
-    StreamString errors;
-    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_STEP));
+    ExecutionContext exe_ctx(thread.shared_from_this());
+    DiagnosticManager diagnostics;
+    Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
     lldb::addr_t args_addr = LLDB_INVALID_ADDRESS;
     FunctionCaller *impl_function_caller = nullptr;
 
@@ -768,11 +769,14 @@ AppleObjCTrampolineHandler::SetupDispatchFunction (Thread &thread, ValueList &di
                     m_impl_code.reset();
                     return args_addr;
                 }
-                
-                if (!m_impl_code->Install(errors, exe_ctx))
+
+                if (!m_impl_code->Install(diagnostics, exe_ctx))
                 {
                     if (log)
-                        log->Printf ("Failed to install implementation lookup: %s.", errors.GetData());
+                    {
+                        log->Printf("Failed to install implementation lookup.");
+                        diagnostics.Dump(log);
+                    }
                     m_impl_code.reset();
                     return args_addr;
                 }
@@ -781,10 +785,8 @@ AppleObjCTrampolineHandler::SetupDispatchFunction (Thread &thread, ValueList &di
             {
                 if (log)
                     log->Printf("No method lookup implementation code.");
-                errors.Printf ("No method lookup implementation code found.");
                 return LLDB_INVALID_ADDRESS;
             }
-            
 
             // Next make the runner function for our implementation utility function.
             ClangASTContext *clang_ast_context = thread.GetProcess()->GetTarget().GetScratchClangASTContext();
@@ -806,20 +808,23 @@ AppleObjCTrampolineHandler::SetupDispatchFunction (Thread &thread, ValueList &di
             impl_function_caller = m_impl_code->GetFunctionCaller();
         }
     }
-    
-    errors.Clear();
-    
+
+    diagnostics.Clear();
+
     // Now write down the argument values for this particular call.  This looks like it might be a race condition
     // if other threads were calling into here, but actually it isn't because we allocate a new args structure for
     // this call by passing args_addr = LLDB_INVALID_ADDRESS...
 
-    if (impl_function_caller->WriteFunctionArguments (exe_ctx, args_addr, dispatch_values, errors))
+    if (impl_function_caller->WriteFunctionArguments(exe_ctx, args_addr, dispatch_values, diagnostics))
     {
         if (log)
-            log->Printf ("Error writing function arguments: \"%s\".", errors.GetData());
+        {
+            log->Printf("Error writing function arguments.");
+            diagnostics.Dump(log);
+        }
         return args_addr;
     }
-        
+
     return args_addr;
 }
 
diff --git a/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleThreadPlanStepThroughObjCTrampoline.cpp b/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleThreadPlanStepThroughObjCTrampoline.cpp
index 285786a09db..a2101c927b4 100644
--- a/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleThreadPlanStepThroughObjCTrampoline.cpp
+++ b/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleThreadPlanStepThroughObjCTrampoline.cpp
@@ -13,16 +13,16 @@
 // Project includes
 #include "AppleThreadPlanStepThroughObjCTrampoline.h"
 #include "AppleObjCTrampolineHandler.h"
-#include "lldb/Target/Process.h"
-#include "lldb/Target/Thread.h"
+#include "lldb/Core/Log.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/FunctionCaller.h"
 #include "lldb/Expression/UtilityFunction.h"
 #include "lldb/Target/ExecutionContext.h"
 #include "lldb/Target/ObjCLanguageRuntime.h"
+#include "lldb/Target/Process.h"
+#include "lldb/Target/Thread.h"
 #include "lldb/Target/ThreadPlanRunToAddress.h"
 #include "lldb/Target/ThreadPlanStepOut.h"
-#include "lldb/Core/Log.h"
-
 
 using namespace lldb;
 using namespace lldb_private;
@@ -75,9 +75,9 @@ AppleThreadPlanStepThroughObjCTrampoline::InitializeFunctionCaller ()
 {
     if (!m_func_sp)
     {
-        StreamString errors;
+        DiagnosticManager diagnostics;
         m_args_addr = m_trampoline_handler->SetupDispatchFunction(m_thread, m_input_values);
-        
+
         if (m_args_addr == LLDB_INVALID_ADDRESS)
         {
             return false;
@@ -89,12 +89,9 @@ AppleThreadPlanStepThroughObjCTrampoline::InitializeFunctionCaller ()
         options.SetIgnoreBreakpoints(true);
         options.SetStopOthers(m_stop_others);
         m_thread.CalculateExecutionContext(exc_ctx);
-        m_func_sp = m_impl_function->GetThreadPlanToCallFunction (exc_ctx,
-                                                                  m_args_addr,
-                                                                  options,
-                                                                  errors);
+        m_func_sp = m_impl_function->GetThreadPlanToCallFunction(exc_ctx, m_args_addr, options, diagnostics);
         m_func_sp->SetOkayToDiscard(true);
-        m_thread.QueueThreadPlan (m_func_sp, false);
+        m_thread.QueueThreadPlan(m_func_sp, false);
     }
     return true;
 }
diff --git a/lldb/source/Plugins/Process/Utility/InferiorCallPOSIX.cpp b/lldb/source/Plugins/Process/Utility/InferiorCallPOSIX.cpp
index 08a1ee74f2d..b694b833cb4 100644
--- a/lldb/source/Plugins/Process/Utility/InferiorCallPOSIX.cpp
+++ b/lldb/source/Plugins/Process/Utility/InferiorCallPOSIX.cpp
@@ -11,6 +11,8 @@
 #include "lldb/Core/Address.h"
 #include "lldb/Core/StreamFile.h"
 #include "lldb/Core/ValueObject.h"
+#include "lldb/Expression/DiagnosticManager.h"
+#include "lldb/Host/Config.h"
 #include "lldb/Symbol/ClangASTContext.h"
 #include "lldb/Symbol/SymbolContext.h"
 #include "lldb/Target/ExecutionContext.h"
@@ -18,7 +20,6 @@
 #include "lldb/Target/Process.h"
 #include "lldb/Target/Target.h"
 #include "lldb/Target/ThreadPlanCallFunction.h"
-#include "lldb/Host/Config.h"
 
 #ifndef LLDB_DISABLE_POSIX
 #include <sys/mman.h>
@@ -96,27 +97,21 @@ lldb_private::InferiorCallMmap (Process *process,
                 ClangASTContext *clang_ast_context = process->GetTarget().GetScratchClangASTContext();
                 CompilerType clang_void_ptr_type = clang_ast_context->GetBasicType(eBasicTypeVoid).GetPointerType();
                 lldb::addr_t args[] = { addr, length, prot_arg, flags_arg, fd, offset };
-                lldb::ThreadPlanSP call_plan_sp (new ThreadPlanCallFunction (*thread,
-                                                                             mmap_range.GetBaseAddress(),
-                                                                             clang_void_ptr_type,
-                                                                             args,
-                                                                             options));
+                lldb::ThreadPlanSP call_plan_sp(new ThreadPlanCallFunction(*thread, mmap_range.GetBaseAddress(),
+                                                                           clang_void_ptr_type, args, options));
                 if (call_plan_sp)
                 {
-                    StreamFile error_strm;
-                    
-                    StackFrame *frame = thread->GetStackFrameAtIndex (0).get();
+                    DiagnosticManager diagnostics;
+
+                    StackFrame *frame = thread->GetStackFrameAtIndex(0).get();
                     if (frame)
                     {
                         ExecutionContext exe_ctx;
                         frame->CalculateExecutionContext (exe_ctx);
-                        ExpressionResults result = process->RunThreadPlan (exe_ctx,
-                                                                          call_plan_sp,
-                                                                          options,
-                                                                          error_strm);
+                        ExpressionResults result = process->RunThreadPlan(exe_ctx, call_plan_sp, options, diagnostics);
                         if (result == eExpressionCompleted)
                         {
-                            
+
                             allocated_addr = call_plan_sp->GetReturnValueObject()->GetValueAsUnsigned(LLDB_INVALID_ADDRESS);
                             if (process->GetAddressByteSize() == 4)
                             {
@@ -179,24 +174,18 @@ lldb_private::InferiorCallMunmap (Process *process,
             if (sc.GetAddressRange(range_scope, 0, use_inline_block_range, munmap_range))
             {
                 lldb::addr_t args[] = { addr, length };
-                lldb::ThreadPlanSP call_plan_sp (new ThreadPlanCallFunction (*thread,
-                                                                            munmap_range.GetBaseAddress(),
-                                                                            CompilerType(),
-                                                                            args,
-                                                                            options));
+                lldb::ThreadPlanSP call_plan_sp(
+                    new ThreadPlanCallFunction(*thread, munmap_range.GetBaseAddress(), CompilerType(), args, options));
                 if (call_plan_sp)
                 {
-                    StreamFile error_strm;
-                   
-                    StackFrame *frame = thread->GetStackFrameAtIndex (0).get();
+                    DiagnosticManager diagnostics;
+
+                    StackFrame *frame = thread->GetStackFrameAtIndex(0).get();
                     if (frame)
                     {
                         ExecutionContext exe_ctx;
                         frame->CalculateExecutionContext (exe_ctx);
-                        ExpressionResults result = process->RunThreadPlan (exe_ctx,
-                                                                          call_plan_sp,
-                                                                          options,
-                                                                          error_strm);
+                        ExpressionResults result = process->RunThreadPlan(exe_ctx, call_plan_sp, options, diagnostics);
                         if (result == eExpressionCompleted)
                         {
                             return true;
@@ -234,24 +223,18 @@ lldb_private::InferiorCall (Process *process,
 
     ClangASTContext *clang_ast_context = process->GetTarget().GetScratchClangASTContext();
     CompilerType clang_void_ptr_type = clang_ast_context->GetBasicType(eBasicTypeVoid).GetPointerType();
-    lldb::ThreadPlanSP call_plan_sp (new ThreadPlanCallFunction (*thread,
-                                                                 *address,
-                                                                 clang_void_ptr_type,
-                                                                 llvm::ArrayRef<addr_t>(),
-                                                                 options));
+    lldb::ThreadPlanSP call_plan_sp(
+        new ThreadPlanCallFunction(*thread, *address, clang_void_ptr_type, llvm::ArrayRef<addr_t>(), options));
     if (call_plan_sp)
     {
-        StreamString error_strm;
+        DiagnosticManager diagnostics;
 
-        StackFrame *frame = thread->GetStackFrameAtIndex (0).get();
+        StackFrame *frame = thread->GetStackFrameAtIndex(0).get();
         if (frame)
         {
             ExecutionContext exe_ctx;
             frame->CalculateExecutionContext (exe_ctx);
-            ExpressionResults result = process->RunThreadPlan (exe_ctx,
-                                                              call_plan_sp,
-                                                              options,
-                                                              error_strm);
+            ExpressionResults result = process->RunThreadPlan(exe_ctx, call_plan_sp, options, diagnostics);
             if (result == eExpressionCompleted)
             {
                 returned_func = call_plan_sp->GetReturnValueObject()->GetValueAsUnsigned(LLDB_INVALID_ADDRESS);
diff --git a/lldb/source/Plugins/SystemRuntime/MacOSX/AppleGetItemInfoHandler.cpp b/lldb/source/Plugins/SystemRuntime/MacOSX/AppleGetItemInfoHandler.cpp
index 2ca367c0cce..19f89f077cd 100644
--- a/lldb/source/Plugins/SystemRuntime/MacOSX/AppleGetItemInfoHandler.cpp
+++ b/lldb/source/Plugins/SystemRuntime/MacOSX/AppleGetItemInfoHandler.cpp
@@ -19,6 +19,7 @@
 #include "lldb/Core/Module.h"
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/Value.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/FunctionCaller.h"
 #include "lldb/Expression/UtilityFunction.h"
 #include "lldb/Symbol/ClangASTContext.h"
@@ -132,11 +133,11 @@ AppleGetItemInfoHandler::Detach ()
 // make the function call.
 
 lldb::addr_t
-AppleGetItemInfoHandler::SetupGetItemInfoFunction (Thread &thread, ValueList &get_item_info_arglist)
+AppleGetItemInfoHandler::SetupGetItemInfoFunction(Thread &thread, ValueList &get_item_info_arglist)
 {
-    ExecutionContext exe_ctx (thread.shared_from_this());
-    StreamString errors;
-    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_SYSTEM_RUNTIME));
+    ExecutionContext exe_ctx(thread.shared_from_this());
+    DiagnosticManager diagnostics;
+    Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_SYSTEM_RUNTIME));
     lldb::addr_t args_addr = LLDB_INVALID_ADDRESS;
     FunctionCaller *get_item_info_caller = nullptr;
 
@@ -161,11 +162,14 @@ AppleGetItemInfoHandler::SetupGetItemInfoFunction (Thread &thread, ValueList &ge
                         log->Printf ("Failed to get utility function: %s.", error.AsCString());
                     return args_addr;
                 }
-                
-                if (!m_get_item_info_impl_code->Install(errors, exe_ctx))
+
+                if (!m_get_item_info_impl_code->Install(diagnostics, exe_ctx))
                 {
                     if (log)
-                        log->Printf ("Failed to install get-item-info introspection: %s.", errors.GetData());
+                    {
+                        log->Printf("Failed to install get-item-info introspection.");
+                        diagnostics.Dump(log);
+                    }
                     m_get_item_info_impl_code.reset();
                     return args_addr;
                 }
@@ -174,7 +178,6 @@ AppleGetItemInfoHandler::SetupGetItemInfoFunction (Thread &thread, ValueList &ge
             {
                 if (log)
                     log->Printf("No get-item-info introspection code found.");
-                errors.Printf ("No get-item-info introspection code found.");
                 return LLDB_INVALID_ADDRESS;
             }
 
@@ -207,20 +210,24 @@ AppleGetItemInfoHandler::SetupGetItemInfoFunction (Thread &thread, ValueList &ge
             }
         }
     }
-    
-    errors.Clear();
-    
+
+    diagnostics.Clear();
+
     // Now write down the argument values for this particular call.  This looks like it might be a race condition
     // if other threads were calling into here, but actually it isn't because we allocate a new args structure for
     // this call by passing args_addr = LLDB_INVALID_ADDRESS...
 
-    if (!get_item_info_caller->WriteFunctionArguments (exe_ctx, args_addr, get_item_info_arglist, errors))
+    if (!get_item_info_caller->WriteFunctionArguments(exe_ctx, args_addr, get_item_info_arglist, diagnostics))
     {
         if (log)
-            log->Printf ("Error writing get-item-info function arguments: \"%s\".", errors.GetData());
+        {
+            log->Printf("Error writing get-item-info function arguments.");
+            diagnostics.Dump(log);
+        }
+
         return args_addr;
     }
-        
+
     return args_addr;
 }
 
@@ -322,12 +329,12 @@ AppleGetItemInfoHandler::GetItemInfo (Thread &thread, uint64_t item, addr_t page
     page_to_free_size_value.GetScalar() = page_to_free_size;
     argument_values.PushValue (page_to_free_size_value);
 
-    addr_t args_addr = SetupGetItemInfoFunction (thread, argument_values);
+    addr_t args_addr = SetupGetItemInfoFunction(thread, argument_values);
 
-    StreamString errors;
+    DiagnosticManager diagnostics;
     ExecutionContext exe_ctx;
     EvaluateExpressionOptions options;
-    options.SetUnwindOnError (true);
+    options.SetUnwindOnError(true);
     options.SetIgnoreBreakpoints (true);
     options.SetStopOthers (true);
     options.SetTimeoutUsec(500000);
@@ -351,8 +358,8 @@ AppleGetItemInfoHandler::GetItemInfo (Thread &thread, uint64_t item, addr_t page
         error.SetErrorString("Could not retrieve function caller for __introspection_dispatch_queue_item_get_info.");
         return return_value;
     }
-    
-    func_call_ret =  func_caller->ExecuteFunction (exe_ctx, &args_addr, options, errors, results);
+
+    func_call_ret = func_caller->ExecuteFunction(exe_ctx, &args_addr, options, diagnostics, results);
     if (func_call_ret != eExpressionCompleted || !error.Success())
     {
         if (log)
diff --git a/lldb/source/Plugins/SystemRuntime/MacOSX/AppleGetPendingItemsHandler.cpp b/lldb/source/Plugins/SystemRuntime/MacOSX/AppleGetPendingItemsHandler.cpp
index 97699878f5e..cda7264d17b 100644
--- a/lldb/source/Plugins/SystemRuntime/MacOSX/AppleGetPendingItemsHandler.cpp
+++ b/lldb/source/Plugins/SystemRuntime/MacOSX/AppleGetPendingItemsHandler.cpp
@@ -19,6 +19,7 @@
 #include "lldb/Core/Module.h"
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/Value.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/FunctionCaller.h"
 #include "lldb/Expression/UtilityFunction.h"
 #include "lldb/Symbol/ClangASTContext.h"
@@ -136,14 +137,14 @@ AppleGetPendingItemsHandler::Detach ()
 // make the function call.
 
 lldb::addr_t
-AppleGetPendingItemsHandler::SetupGetPendingItemsFunction (Thread &thread, ValueList &get_pending_items_arglist)
+AppleGetPendingItemsHandler::SetupGetPendingItemsFunction(Thread &thread, ValueList &get_pending_items_arglist)
 {
-    ExecutionContext exe_ctx (thread.shared_from_this());
-    StreamString errors;
-    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_SYSTEM_RUNTIME));
+    ExecutionContext exe_ctx(thread.shared_from_this());
+    DiagnosticManager diagnostics;
+    Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_SYSTEM_RUNTIME));
     lldb::addr_t args_addr = LLDB_INVALID_ADDRESS;
     FunctionCaller *get_pending_items_caller = nullptr;
-    
+
     // Scope for mutex locker:
     {
         Mutex::Locker locker(m_get_pending_items_function_mutex);
@@ -165,11 +166,14 @@ AppleGetPendingItemsHandler::SetupGetPendingItemsFunction (Thread &thread, Value
                         log->Printf ("Failed to get UtilityFunction for pending-items introspection: %s.", error.AsCString());
                     return args_addr;
                 }
-                
-                if (!m_get_pending_items_impl_code->Install(errors, exe_ctx))
+
+                if (!m_get_pending_items_impl_code->Install(diagnostics, exe_ctx))
                 {
                     if (log)
-                        log->Printf ("Failed to install pending-items introspection: %s.", errors.GetData());
+                    {
+                        log->Printf("Failed to install pending-items introspection.");
+                        diagnostics.Dump(log);
+                    }
                     m_get_pending_items_impl_code.reset();
                     return args_addr;
                 }
@@ -196,11 +200,10 @@ AppleGetPendingItemsHandler::SetupGetPendingItemsFunction (Thread &thread, Value
                 return args_addr;
             }
         }
-
     }
-    
-    errors.Clear();
-    
+
+    diagnostics.Clear();
+
     if (get_pending_items_caller == nullptr)
     {
         if (log)
@@ -212,13 +215,17 @@ AppleGetPendingItemsHandler::SetupGetPendingItemsFunction (Thread &thread, Value
     // if other threads were calling into here, but actually it isn't because we allocate a new args structure for
     // this call by passing args_addr = LLDB_INVALID_ADDRESS...
 
-    if (!get_pending_items_caller->WriteFunctionArguments (exe_ctx, args_addr, get_pending_items_arglist, errors))
+    if (!get_pending_items_caller->WriteFunctionArguments(exe_ctx, args_addr, get_pending_items_arglist, diagnostics))
     {
         if (log)
-            log->Printf ("Error writing pending-items function arguments: \"%s\".", errors.GetData());
+        {
+            log->Printf("Error writing pending-items function arguments.");
+            diagnostics.Dump(log);
+        }
+
         return args_addr;
     }
-        
+
     return args_addr;
 }
 
@@ -322,12 +329,12 @@ AppleGetPendingItemsHandler::GetPendingItems (Thread &thread, addr_t queue, addr
     page_to_free_size_value.GetScalar() = page_to_free_size;
     argument_values.PushValue (page_to_free_size_value);
 
-    addr_t args_addr = SetupGetPendingItemsFunction (thread, argument_values);
+    addr_t args_addr = SetupGetPendingItemsFunction(thread, argument_values);
 
-    StreamString errors;
+    DiagnosticManager diagnostics;
     ExecutionContext exe_ctx;
     FunctionCaller *get_pending_items_caller = m_get_pending_items_impl_code->GetFunctionCaller();
-    
+
     EvaluateExpressionOptions options;
     options.SetUnwindOnError (true);
     options.SetIgnoreBreakpoints (true);
@@ -342,10 +349,9 @@ AppleGetPendingItemsHandler::GetPendingItems (Thread &thread, addr_t queue, addr
         return return_value;
     }
 
-
     ExpressionResults func_call_ret;
     Value results;
-    func_call_ret =  get_pending_items_caller->ExecuteFunction (exe_ctx, &args_addr, options, errors, results);
+    func_call_ret = get_pending_items_caller->ExecuteFunction(exe_ctx, &args_addr, options, diagnostics, results);
     if (func_call_ret != eExpressionCompleted || !error.Success())
     {
         if (log)
diff --git a/lldb/source/Plugins/SystemRuntime/MacOSX/AppleGetQueuesHandler.cpp b/lldb/source/Plugins/SystemRuntime/MacOSX/AppleGetQueuesHandler.cpp
index 3370b3257a2..e005d500e0c 100644
--- a/lldb/source/Plugins/SystemRuntime/MacOSX/AppleGetQueuesHandler.cpp
+++ b/lldb/source/Plugins/SystemRuntime/MacOSX/AppleGetQueuesHandler.cpp
@@ -18,6 +18,7 @@
 #include "lldb/Core/Module.h"
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/Value.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/FunctionCaller.h"
 #include "lldb/Expression/UtilityFunction.h"
 #include "lldb/Symbol/ClangASTContext.h"
@@ -146,12 +147,12 @@ AppleGetQueuesHandler::Detach ()
 lldb::addr_t
 AppleGetQueuesHandler::SetupGetQueuesFunction (Thread &thread, ValueList &get_queues_arglist)
 {
-    ExecutionContext exe_ctx (thread.shared_from_this());
+    ExecutionContext exe_ctx(thread.shared_from_this());
     Address impl_code_address;
-    StreamString errors;
-    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_SYSTEM_RUNTIME));
+    DiagnosticManager diagnostics;
+    Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_SYSTEM_RUNTIME));
     lldb::addr_t args_addr = LLDB_INVALID_ADDRESS;
-    
+
     FunctionCaller *get_queues_caller = nullptr;
 
     // Scope for mutex locker:
@@ -175,11 +176,14 @@ AppleGetQueuesHandler::SetupGetQueuesFunction (Thread &thread, ValueList &get_qu
                         log->Printf ("Failed to get UtilityFunction for queues introspection: %s.", error.AsCString());
                     return args_addr;
                 }
-                
-                if (!m_get_queues_impl_code_up->Install(errors, exe_ctx))
+
+                if (!m_get_queues_impl_code_up->Install(diagnostics, exe_ctx))
                 {
                     if (log)
-                        log->Printf ("Failed to install queues introspection: %s.", errors.GetData());
+                    {
+                        log->Printf("Failed to install queues introspection");
+                        diagnostics.Dump(log);
+                    }
                     m_get_queues_impl_code_up.reset();
                     return args_addr;
                 }
@@ -187,12 +191,14 @@ AppleGetQueuesHandler::SetupGetQueuesFunction (Thread &thread, ValueList &get_qu
             else
             {
                 if (log)
+                {
                     log->Printf("No queues introspection code found.");
-                errors.Printf ("No queues introspection code found.");
+                    diagnostics.Dump(log);
+                }
                 return LLDB_INVALID_ADDRESS;
             }
         }
-        
+
         // Next make the runner function for our implementation utility function.
         ClangASTContext *clang_ast_context = thread.GetProcess()->GetTarget().GetScratchClangASTContext();
         CompilerType get_queues_return_type = clang_ast_context->GetBasicType(eBasicTypeVoid).GetPointerType();
@@ -207,20 +213,23 @@ AppleGetQueuesHandler::SetupGetQueuesFunction (Thread &thread, ValueList &get_qu
             return args_addr;
         }
     }
-    
-    errors.Clear();
-    
+
+    diagnostics.Clear();
+
     // Now write down the argument values for this particular call.  This looks like it might be a race condition
     // if other threads were calling into here, but actually it isn't because we allocate a new args structure for
     // this call by passing args_addr = LLDB_INVALID_ADDRESS...
 
-    if (!get_queues_caller->WriteFunctionArguments (exe_ctx, args_addr, get_queues_arglist, errors))
+    if (!get_queues_caller->WriteFunctionArguments(exe_ctx, args_addr, get_queues_arglist, diagnostics))
     {
         if (log)
-            log->Printf ("Error writing get-queues function arguments: \"%s\".", errors.GetData());
+        {
+            log->Printf("Error writing get-queues function arguments.");
+            diagnostics.Dump(log);
+        }
         return args_addr;
     }
-        
+
     return args_addr;
 }
 
@@ -332,10 +341,10 @@ AppleGetQueuesHandler::GetCurrentQueues (Thread &thread, addr_t page_to_free, ui
         return return_value;
     }
 
-    StreamString errors;
+    DiagnosticManager diagnostics;
     ExecutionContext exe_ctx;
     EvaluateExpressionOptions options;
-    options.SetUnwindOnError (true);
+    options.SetUnwindOnError(true);
     options.SetIgnoreBreakpoints (true);
     options.SetStopOthers (true);
     options.SetTimeoutUsec(500000);
@@ -344,7 +353,7 @@ AppleGetQueuesHandler::GetCurrentQueues (Thread &thread, addr_t page_to_free, ui
 
     ExpressionResults func_call_ret;
     Value results;
-    func_call_ret =  get_queues_caller->ExecuteFunction (exe_ctx, &args_addr, options, errors, results);
+    func_call_ret = get_queues_caller->ExecuteFunction(exe_ctx, &args_addr, options, diagnostics, results);
     if (func_call_ret != eExpressionCompleted || !error.Success())
     {
         if (log)
diff --git a/lldb/source/Plugins/SystemRuntime/MacOSX/AppleGetThreadItemInfoHandler.cpp b/lldb/source/Plugins/SystemRuntime/MacOSX/AppleGetThreadItemInfoHandler.cpp
index ba03f51152c..a528dafb97a 100644
--- a/lldb/source/Plugins/SystemRuntime/MacOSX/AppleGetThreadItemInfoHandler.cpp
+++ b/lldb/source/Plugins/SystemRuntime/MacOSX/AppleGetThreadItemInfoHandler.cpp
@@ -14,12 +14,12 @@
 // Other libraries and framework includes
 // Project includes
 
-#include "lldb/lldb-private.h"
 #include "lldb/Core/ConstString.h"
 #include "lldb/Core/Log.h"
 #include "lldb/Core/Module.h"
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/Value.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/Expression.h"
 #include "lldb/Expression/FunctionCaller.h"
 #include "lldb/Expression/UtilityFunction.h"
@@ -30,6 +30,7 @@
 #include "lldb/Target/StackFrame.h"
 #include "lldb/Target/Target.h"
 #include "lldb/Target/Thread.h"
+#include "lldb/lldb-private.h"
 
 using namespace lldb;
 using namespace lldb_private;
@@ -141,10 +142,10 @@ AppleGetThreadItemInfoHandler::Detach ()
 lldb::addr_t
 AppleGetThreadItemInfoHandler::SetupGetThreadItemInfoFunction (Thread &thread, ValueList &get_thread_item_info_arglist)
 {
-    ExecutionContext exe_ctx (thread.shared_from_this());
+    ExecutionContext exe_ctx(thread.shared_from_this());
     Address impl_code_address;
-    StreamString errors;
-    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_SYSTEM_RUNTIME));
+    DiagnosticManager diagnostics;
+    Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_SYSTEM_RUNTIME));
     lldb::addr_t args_addr = LLDB_INVALID_ADDRESS;
     FunctionCaller *get_thread_item_info_caller = nullptr;
 
@@ -171,11 +172,15 @@ AppleGetThreadItemInfoHandler::SetupGetThreadItemInfoFunction (Thread &thread, V
                     m_get_thread_item_info_impl_code.reset();
                     return args_addr;
                 }
-                
-                if (!m_get_thread_item_info_impl_code->Install(errors, exe_ctx))
+
+                if (!m_get_thread_item_info_impl_code->Install(diagnostics, exe_ctx))
                 {
                     if (log)
-                        log->Printf ("Failed to install get-thread-item-info introspection: %s.", errors.GetData());
+                    {
+                        log->Printf("Failed to install get-thread-item-info introspection.");
+                        diagnostics.Dump(log);
+                    }
+
                     m_get_thread_item_info_impl_code.reset();
                     return args_addr;
                 }
@@ -184,10 +189,9 @@ AppleGetThreadItemInfoHandler::SetupGetThreadItemInfoFunction (Thread &thread, V
             {
                 if (log)
                     log->Printf("No get-thread-item-info introspection code found.");
-                errors.Printf ("No get-thread-item-info introspection code found.");
                 return LLDB_INVALID_ADDRESS;
             }
-            
+
             // Also make the FunctionCaller for this UtilityFunction:
             
             ClangASTContext *clang_ast_context = thread.GetProcess()->GetTarget().GetScratchClangASTContext();
@@ -210,20 +214,24 @@ AppleGetThreadItemInfoHandler::SetupGetThreadItemInfoFunction (Thread &thread, V
             get_thread_item_info_caller = m_get_thread_item_info_impl_code->GetFunctionCaller();
         }
     }
-    
-    errors.Clear();
-    
+
+    diagnostics.Clear();
+
     // Now write down the argument values for this particular call.  This looks like it might be a race condition
     // if other threads were calling into here, but actually it isn't because we allocate a new args structure for
     // this call by passing args_addr = LLDB_INVALID_ADDRESS...
 
-    if (!get_thread_item_info_caller->WriteFunctionArguments (exe_ctx, args_addr, get_thread_item_info_arglist, errors))
+    if (!get_thread_item_info_caller->WriteFunctionArguments(exe_ctx, args_addr, get_thread_item_info_arglist,
+                                                             diagnostics))
     {
         if (log)
-            log->Printf ("Error writing get-thread-item-info function arguments: \"%s\".", errors.GetData());
+        {
+            log->Printf("Error writing get-thread-item-info function arguments");
+            diagnostics.Dump(log);
+        }
         return args_addr;
     }
-        
+
     return args_addr;
 }
 
@@ -324,13 +332,13 @@ AppleGetThreadItemInfoHandler::GetThreadItemInfo (Thread &thread, tid_t thread_i
     page_to_free_size_value.GetScalar() = page_to_free_size;
     argument_values.PushValue (page_to_free_size_value);
 
-    addr_t args_addr = SetupGetThreadItemInfoFunction (thread, argument_values);
+    addr_t args_addr = SetupGetThreadItemInfoFunction(thread, argument_values);
 
-    StreamString errors;
+    DiagnosticManager diagnostics;
     ExecutionContext exe_ctx;
     EvaluateExpressionOptions options;
     FunctionCaller *get_thread_item_info_caller = nullptr;
-    
+
     options.SetUnwindOnError (true);
     options.SetIgnoreBreakpoints (true);
     options.SetStopOthers (true);
@@ -354,7 +362,7 @@ AppleGetThreadItemInfoHandler::GetThreadItemInfo (Thread &thread, tid_t thread_i
 
     ExpressionResults func_call_ret;
     Value results;
-    func_call_ret =  get_thread_item_info_caller->ExecuteFunction (exe_ctx, &args_addr, options, errors, results);
+    func_call_ret = get_thread_item_info_caller->ExecuteFunction(exe_ctx, &args_addr, options, diagnostics, results);
     if (func_call_ret != eExpressionCompleted || !error.Success())
     {
         if (log)
diff --git a/lldb/source/Symbol/ClangASTContext.cpp b/lldb/source/Symbol/ClangASTContext.cpp
index a5c119b8398..1b7e6b153ba 100644
--- a/lldb/source/Symbol/ClangASTContext.cpp
+++ b/lldb/source/Symbol/ClangASTContext.cpp
@@ -685,8 +685,9 @@ public:
     {
         m_log = lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS);
     }
-    
-    void HandleDiagnostic (DiagnosticsEngine::Level DiagLevel, const Diagnostic &info)
+
+    void
+    HandleDiagnostic(DiagnosticsEngine::Level DiagLevel, const clang::Diagnostic &info)
     {
         if (m_log)
         {
diff --git a/lldb/source/Target/Process.cpp b/lldb/source/Target/Process.cpp
index 4b03176bdc9..4f15d5880a6 100644
--- a/lldb/source/Target/Process.cpp
+++ b/lldb/source/Target/Process.cpp
@@ -14,19 +14,20 @@
 
 // Other libraries and framework includes
 // Project includes
-#include "lldb/Target/Process.h"
-#include "lldb/Breakpoint/StoppointCallbackContext.h"
+#include "Plugins/Process/Utility/InferiorCallPOSIX.h"
 #include "lldb/Breakpoint/BreakpointLocation.h"
-#include "lldb/Core/Event.h"
+#include "lldb/Breakpoint/StoppointCallbackContext.h"
 #include "lldb/Core/Debugger.h"
+#include "lldb/Core/Event.h"
 #include "lldb/Core/Log.h"
 #include "lldb/Core/Module.h"
 #include "lldb/Core/ModuleSpec.h"
 #include "lldb/Core/PluginManager.h"
 #include "lldb/Core/State.h"
 #include "lldb/Core/StreamFile.h"
-#include "lldb/Expression/UserExpression.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/IRDynamicChecks.h"
+#include "lldb/Expression/UserExpression.h"
 #include "lldb/Host/ConnectionFileDescriptor.h"
 #include "lldb/Host/FileSystem.h"
 #include "lldb/Host/Host.h"
@@ -39,17 +40,18 @@
 #include "lldb/Symbol/Function.h"
 #include "lldb/Symbol/Symbol.h"
 #include "lldb/Target/ABI.h"
+#include "lldb/Target/CPPLanguageRuntime.h"
 #include "lldb/Target/DynamicLoader.h"
 #include "lldb/Target/InstrumentationRuntime.h"
 #include "lldb/Target/JITLoader.h"
 #include "lldb/Target/JITLoaderList.h"
+#include "lldb/Target/LanguageRuntime.h"
 #include "lldb/Target/MemoryHistory.h"
 #include "lldb/Target/MemoryRegionInfo.h"
-#include "lldb/Target/OperatingSystem.h"
-#include "lldb/Target/LanguageRuntime.h"
-#include "lldb/Target/CPPLanguageRuntime.h"
 #include "lldb/Target/ObjCLanguageRuntime.h"
+#include "lldb/Target/OperatingSystem.h"
 #include "lldb/Target/Platform.h"
+#include "lldb/Target/Process.h"
 #include "lldb/Target/RegisterContext.h"
 #include "lldb/Target/StopInfo.h"
 #include "lldb/Target/SystemRuntime.h"
@@ -60,7 +62,6 @@
 #include "lldb/Target/ThreadPlanBase.h"
 #include "lldb/Target/UnixSignals.h"
 #include "lldb/Utility/NameMatches.h"
-#include "Plugins/Process/Utility/InferiorCallPOSIX.h"
 
 using namespace lldb;
 using namespace lldb_private;
@@ -5194,35 +5195,33 @@ namespace
 } // anonymous namespace
 
 ExpressionResults
-Process::RunThreadPlan (ExecutionContext &exe_ctx,
-                        lldb::ThreadPlanSP &thread_plan_sp,
-                        const EvaluateExpressionOptions &options,
-                        Stream &errors)
+Process::RunThreadPlan(ExecutionContext &exe_ctx, lldb::ThreadPlanSP &thread_plan_sp,
+                       const EvaluateExpressionOptions &options, DiagnosticManager &diagnostic_manager)
 {
     ExpressionResults return_value = eExpressionSetupError;
 
     if (!thread_plan_sp)
     {
-        errors.Printf("RunThreadPlan called with empty thread plan.");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "RunThreadPlan called with empty thread plan.");
         return eExpressionSetupError;
     }
 
     if (!thread_plan_sp->ValidatePlan(nullptr))
     {
-        errors.Printf ("RunThreadPlan called with an invalid thread plan.");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "RunThreadPlan called with an invalid thread plan.");
         return eExpressionSetupError;
     }
 
     if (exe_ctx.GetProcessPtr() != this)
     {
-        errors.Printf("RunThreadPlan called on wrong process.");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "RunThreadPlan called on wrong process.");
         return eExpressionSetupError;
     }
 
     Thread *thread = exe_ctx.GetThreadPtr();
     if (thread == nullptr)
     {
-        errors.Printf("RunThreadPlan called with invalid thread.");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "RunThreadPlan called with invalid thread.");
         return eExpressionSetupError;
     }
 
@@ -5245,7 +5244,8 @@ Process::RunThreadPlan (ExecutionContext &exe_ctx,
 
     if (m_private_state.GetValue() != eStateStopped)
     {
-        errors.Printf ("RunThreadPlan called while the private state was not stopped.");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError,
+                                      "RunThreadPlan called while the private state was not stopped.");
         return eExpressionSetupError;
     }
 
@@ -5258,7 +5258,8 @@ Process::RunThreadPlan (ExecutionContext &exe_ctx,
         selected_frame_sp = thread->GetSelectedFrame();
         if (!selected_frame_sp)
         {
-            errors.Printf("RunThreadPlan called without a selected frame on thread %d", thread_idx_id);
+            diagnostic_manager.Printf(eDiagnosticSeverityError,
+                                      "RunThreadPlan called without a selected frame on thread %d", thread_idx_id);
             return eExpressionSetupError;
         }
     }
@@ -5400,7 +5401,9 @@ Process::RunThreadPlan (ExecutionContext &exe_ctx,
                 {
                     if (timeout_usec < option_one_thread_timeout)
                     {
-                        errors.Printf("RunThreadPlan called without one thread timeout greater than total timeout");
+                        diagnostic_manager.PutCString(
+                            eDiagnosticSeverityError,
+                            "RunThreadPlan called without one thread timeout greater than total timeout");
                         return eExpressionSetupError;
                     }
                     computed_one_thread_timeout = option_one_thread_timeout;
@@ -5431,7 +5434,8 @@ Process::RunThreadPlan (ExecutionContext &exe_ctx,
         Event *other_events = listener_sp->PeekAtNextEvent();
         if (other_events != nullptr)
         {
-            errors.Printf("Calling RunThreadPlan with pending events on the queue.");
+            diagnostic_manager.PutCString(eDiagnosticSeverityError,
+                                          "RunThreadPlan called with pending events on the queue.");
             return eExpressionSetupError;
         }
 
@@ -5473,12 +5477,12 @@ Process::RunThreadPlan (ExecutionContext &exe_ctx,
                 if (do_resume)
                 {
                     num_resumes++;
-                    Error resume_error = PrivateResume ();
+                    Error resume_error = PrivateResume();
                     if (!resume_error.Success())
                     {
-                        errors.Printf("Error resuming inferior the %d time: \"%s\".\n",
-                                      num_resumes,
-                                      resume_error.AsCString());
+                        diagnostic_manager.Printf(eDiagnosticSeverityError,
+                                                  "couldn't resume inferior the %d time: \"%s\".", num_resumes,
+                                                  resume_error.AsCString());
                         return_value = eExpressionSetupError;
                         break;
                     }
@@ -5491,10 +5495,11 @@ Process::RunThreadPlan (ExecutionContext &exe_ctx,
                 if (!got_event)
                 {
                     if (log)
-                        log->Printf ("Process::RunThreadPlan(): didn't get any event after resume %d, exiting.",
-                                        num_resumes);
+                        log->Printf("Process::RunThreadPlan(): didn't get any event after resume %" PRIu32 ", exiting.",
+                                    num_resumes);
 
-                    errors.Printf("Didn't get any event after resume %d, exiting.", num_resumes);
+                    diagnostic_manager.Printf(eDiagnosticSeverityError,
+                                              "didn't get any event after resume %" PRIu32 ", exiting.", num_resumes);
                     return_value = eExpressionSetupError;
                     break;
                 }
@@ -5527,8 +5532,9 @@ Process::RunThreadPlan (ExecutionContext &exe_ctx,
                         Halt(clear_thread_plans, use_run_lock);
                     }
 
-                    errors.Printf("Didn't get running event after initial resume, got %s instead.",
-                                  StateAsCString(stop_state));
+                    diagnostic_manager.Printf(eDiagnosticSeverityError,
+                                              "didn't get running event after initial resume, got %s instead.",
+                                              StateAsCString(stop_state));
                     return_value = eExpressionSetupError;
                     break;
                 }
@@ -5622,9 +5628,10 @@ Process::RunThreadPlan (ExecutionContext &exe_ctx,
                         const bool use_run_lock = false;
                         Halt(clear_thread_plans, use_run_lock);
                         return_value = eExpressionInterrupted;
-                        errors.Printf ("Execution halted by user interrupt.");
+                        diagnostic_manager.PutCString(eDiagnosticSeverityRemark, "execution halted by user interrupt.");
                         if (log)
-                            log->Printf ("Process::RunThreadPlan(): Got  interrupted by eBroadcastBitInterrupted, exiting.");
+                            log->Printf(
+                                "Process::RunThreadPlan(): Got  interrupted by eBroadcastBitInterrupted, exiting.");
                         break;
                     }
                     else
@@ -5727,7 +5734,8 @@ Process::RunThreadPlan (ExecutionContext &exe_ctx,
                             if (stop_state == eStateExited)
                                 event_to_broadcast_sp = event_sp;
 
-                            errors.Printf ("Execution stopped with unexpected state.\n");
+                            diagnostic_manager.PutCString(eDiagnosticSeverityError,
+                                                          "execution stopped with unexpected state.");
                             return_value = eExpressionInterrupted;
                             break;
                         }
diff --git a/lldb/source/Target/ThreadPlanCallUserExpression.cpp b/lldb/source/Target/ThreadPlanCallUserExpression.cpp
index b24f74b10df..d4259ed18d3 100644
--- a/lldb/source/Target/ThreadPlanCallUserExpression.cpp
+++ b/lldb/source/Target/ThreadPlanCallUserExpression.cpp
@@ -19,8 +19,9 @@
 #include "lldb/Core/Address.h"
 #include "lldb/Core/Log.h"
 #include "lldb/Core/Stream.h"
-#include "lldb/Expression/UserExpression.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/IRDynamicChecks.h"
+#include "lldb/Expression/UserExpression.h"
 #include "lldb/Host/HostInfo.h"
 #include "lldb/Target/LanguageRuntime.h"
 #include "lldb/Target/Process.h"
@@ -90,15 +91,16 @@ ThreadPlanCallUserExpression::MischiefManaged ()
 
             function_stack_bottom = function_stack_pointer - HostInfo::GetPageSize();
             function_stack_top = function_stack_pointer;
-            
-            StreamString  error_stream;
-            
+
+            DiagnosticManager diagnostics;
+
             ExecutionContext exe_ctx(GetThread());
 
-            m_user_expression_sp->FinalizeJITExecution(error_stream, exe_ctx, m_result_var_sp, function_stack_bottom, function_stack_top);
+            m_user_expression_sp->FinalizeJITExecution(diagnostics, exe_ctx, m_result_var_sp, function_stack_bottom,
+                                                       function_stack_top);
         }
-        
-        ThreadPlan::MischiefManaged ();
+
+        ThreadPlan::MischiefManaged();
         return true;
     }
     else