Add setting to require hardware breakpoints.

When debugging read-only memory we cannot use software breakpoint. We
already have support for hardware breakpoints and users can specify them
with `-H`. However, there's no option to force LLDB to use hardware
breakpoints internally, for example while stepping.

This patch adds a setting target.require-hardware-breakpoint that forces
LLDB to always use hardware breakpoints. Because hardware breakpoints
are a limited resource and can fail to resolve, this patch also extends
error handling in thread plans, where breakpoints are used for stepping.

Differential revision: https://reviews.llvm.org/D54221

1 files changed, 4 insertions, 2 deletions

diff --git a/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleThreadPlanStepThroughObjCTrampoline.cpp b/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleThreadPlanStepThroughObjCTrampoline.cpp
index d19ab445d4f..19d9676e8b0 100644
--- a/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleThreadPlanStepThroughObjCTrampoline.cpp
+++ b/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleThreadPlanStepThroughObjCTrampoline.cpp
@@ -157,13 +157,15 @@ bool AppleThreadPlanStepThroughObjCTrampoline::ShouldStop(Event *event_ptr) {
 
       SymbolContext sc = m_thread.GetStackFrameAtIndex(0)->GetSymbolContext(
           eSymbolContextEverything);
+      Status status;
       const bool abort_other_plans = false;
       const bool first_insn = true;
       const uint32_t frame_idx = 0;
       m_run_to_sp = m_thread.QueueThreadPlanForStepOutNoShouldStop(
           abort_other_plans, &sc, first_insn, m_stop_others, eVoteNoOpinion,
-          eVoteNoOpinion, frame_idx);
-      m_run_to_sp->SetPrivate(true);
+          eVoteNoOpinion, frame_idx, status);
+      if (m_run_to_sp && status.Success())
+        m_run_to_sp->SetPrivate(true);
       return false;
     }