[clang-tidy] new check 'readability-redundant-preprocessor'

Finds potentially redundant preprocessor directives.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D54349

llvm-svn: 350922

10 files changed, 340 insertions, 0 deletions

diff --git a/clang-tools-extra/clang-tidy/readability/CMakeLists.txt b/clang-tools-extra/clang-tidy/readability/CMakeLists.txt
index c429b8126ce8..b48e307e6153 100644
--- a/clang-tools-extra/clang-tidy/readability/CMakeLists.txt
+++ b/clang-tools-extra/clang-tidy/readability/CMakeLists.txt
@@ -24,6 +24,7 @@ add_clang_library(clangTidyReadabilityModule
   RedundantDeclarationCheck.cpp
   RedundantFunctionPtrDereferenceCheck.cpp
   RedundantMemberInitCheck.cpp
+  RedundantPreprocessorCheck.cpp
   RedundantSmartptrGetCheck.cpp
   RedundantStringCStrCheck.cpp
   RedundantStringInitCheck.cpp
diff --git a/clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp b/clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp
index 8dab29688d21..e032d1f6887c 100644
--- a/clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp
@@ -31,6 +31,7 @@
 #include "RedundantDeclarationCheck.h"
 #include "RedundantFunctionPtrDereferenceCheck.h"
 #include "RedundantMemberInitCheck.h"
+#include "RedundantPreprocessorCheck.h"
 #include "RedundantSmartptrGetCheck.h"
 #include "RedundantStringCStrCheck.h"
 #include "RedundantStringInitCheck.h"
@@ -83,6 +84,8 @@ public:
         "readability-redundant-function-ptr-dereference");
     CheckFactories.registerCheck<RedundantMemberInitCheck>(
         "readability-redundant-member-init");
+    CheckFactories.registerCheck<RedundantPreprocessorCheck>(
+        "readability-redundant-preprocessor");
     CheckFactories.registerCheck<SimplifySubscriptExprCheck>(
         "readability-simplify-subscript-expr");
     CheckFactories.registerCheck<StaticAccessedThroughInstanceCheck>(
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantPreprocessorCheck.cpp b/clang-tools-extra/clang-tidy/readability/RedundantPreprocessorCheck.cpp
new file mode 100644
index 000000000000..352e234644d9
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/readability/RedundantPreprocessorCheck.cpp
@@ -0,0 +1,109 @@
+//===--- RedundantPreprocessorCheck.cpp - clang-tidy ----------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "RedundantPreprocessorCheck.h"
+#include "clang/Frontend/CompilerInstance.h"
+
+namespace clang {
+namespace tidy {
+namespace readability {
+
+namespace {
+/// Information about an opening preprocessor directive.
+struct PreprocessorEntry {
+  SourceLocation Loc;
+  /// Condition used after the preprocessor directive.
+  std::string Condition;
+};
+
+class RedundantPreprocessorCallbacks : public PPCallbacks {
+  enum DirectiveKind { DK_If = 0, DK_Ifdef = 1, DK_Ifndef = 2 };
+
+public:
+  explicit RedundantPreprocessorCallbacks(ClangTidyCheck &Check,
+                                          Preprocessor &PP)
+      : Check(Check), PP(PP),
+        WarningDescription("nested redundant %select{#if|#ifdef|#ifndef}0; "
+                           "consider removing it"),
+        NoteDescription("previous %select{#if|#ifdef|#ifndef}0 was here") {}
+
+  void If(SourceLocation Loc, SourceRange ConditionRange,
+          ConditionValueKind ConditionValue) override {
+    StringRef Condition =
+        Lexer::getSourceText(CharSourceRange::getTokenRange(ConditionRange),
+                             PP.getSourceManager(), PP.getLangOpts());
+    CheckMacroRedundancy(Loc, Condition, IfStack, DK_If, DK_If, true);
+  }
+
+  void Ifdef(SourceLocation Loc, const Token &MacroNameTok,
+             const MacroDefinition &MacroDefinition) override {
+    std::string MacroName = PP.getSpelling(MacroNameTok);
+    CheckMacroRedundancy(Loc, MacroName, IfdefStack, DK_Ifdef, DK_Ifdef, true);
+    CheckMacroRedundancy(Loc, MacroName, IfndefStack, DK_Ifdef, DK_Ifndef,
+                         false);
+  }
+
+  void Ifndef(SourceLocation Loc, const Token &MacroNameTok,
+              const MacroDefinition &MacroDefinition) override {
+    std::string MacroName = PP.getSpelling(MacroNameTok);
+    CheckMacroRedundancy(Loc, MacroName, IfndefStack, DK_Ifndef, DK_Ifndef,
+                         true);
+    CheckMacroRedundancy(Loc, MacroName, IfdefStack, DK_Ifndef, DK_Ifdef,
+                         false);
+  }
+
+  void Endif(SourceLocation Loc, SourceLocation IfLoc) override {
+    if (!IfStack.empty() && IfLoc == IfStack.back().Loc)
+      IfStack.pop_back();
+    if (!IfdefStack.empty() && IfLoc == IfdefStack.back().Loc)
+      IfdefStack.pop_back();
+    if (!IfndefStack.empty() && IfLoc == IfndefStack.back().Loc)
+      IfndefStack.pop_back();
+  }
+
+private:
+  void CheckMacroRedundancy(SourceLocation Loc, StringRef MacroName,
+                            SmallVector<PreprocessorEntry, 4> &Stack,
+                            DirectiveKind WarningKind, DirectiveKind NoteKind,
+                            bool Store) {
+    if (PP.getSourceManager().isInMainFile(Loc)) {
+      for (const auto &Entry : Stack) {
+        if (Entry.Condition == MacroName) {
+          Check.diag(Loc, WarningDescription) << WarningKind;
+          Check.diag(Entry.Loc, NoteDescription, DiagnosticIDs::Note)
+              << NoteKind;
+        }
+      }
+    }
+
+    if (Store)
+      // This is an actual directive to be remembered.
+      Stack.push_back({Loc, MacroName});
+  }
+
+  ClangTidyCheck &Check;
+  Preprocessor &PP;
+  SmallVector<PreprocessorEntry, 4> IfStack;
+  SmallVector<PreprocessorEntry, 4> IfdefStack;
+  SmallVector<PreprocessorEntry, 4> IfndefStack;
+  const std::string WarningDescription;
+  const std::string NoteDescription;
+};
+} // namespace
+
+void RedundantPreprocessorCheck::registerPPCallbacks(
+    CompilerInstance &Compiler) {
+  Compiler.getPreprocessor().addPPCallbacks(
+      ::llvm::make_unique<RedundantPreprocessorCallbacks>(
+          *this, Compiler.getPreprocessor()));
+}
+
+} // namespace readability
+} // namespace tidy
+} // namespace clang
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantPreprocessorCheck.h b/clang-tools-extra/clang-tidy/readability/RedundantPreprocessorCheck.h
new file mode 100644
index 000000000000..d44076568a70
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/readability/RedundantPreprocessorCheck.h
@@ -0,0 +1,35 @@
+//===--- RedundantPreprocessorCheck.h - clang-tidy --------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_REDUNDANTPREPROCESSORCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_REDUNDANTPREPROCESSORCHECK_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace readability {
+
+/// This check flags redundant preprocessor directives: nested directives with
+/// the same condition.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/readability-redundant-preprocessor.html
+class RedundantPreprocessorCheck : public ClangTidyCheck {
+public:
+  RedundantPreprocessorCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  void registerPPCallbacks(CompilerInstance &Compiler) override;
+};
+
+} // namespace readability
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_REDUNDANTPREPROCESSORCHECK_H
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index f6cdc3efbdc0..8731dc73c648 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -244,6 +244,11 @@ Improvements to clang-tidy
   Detects usage of magic numbers, numbers that are used as literals instead of
   introduced via constants or symbols.
 
+- New :doc:`readability-redundant-preprocessor
+  <clang-tidy/checks/readability-redundant-preprocessor>` check.
+
+  Finds potentially redundant preprocessor directives.
+
 - New :doc:`readability-uppercase-literal-suffix
   <clang-tidy/checks/readability-uppercase-literal-suffix>` check.
 
diff --git a/clang-tools-extra/docs/clang-tidy/checks/list.rst b/clang-tools-extra/docs/clang-tidy/checks/list.rst
index b4a60e76c8ef..080e747bdfad 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/list.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/list.rst
@@ -254,6 +254,7 @@ Clang-Tidy Checks
    readability-redundant-declaration
    readability-redundant-function-ptr-dereference
    readability-redundant-member-init
+   readability-redundant-preprocessor
    readability-redundant-smartptr-get
    readability-redundant-string-cstr
    readability-redundant-string-init
diff --git a/clang-tools-extra/docs/clang-tidy/checks/readability-redundant-preprocessor.rst b/clang-tools-extra/docs/clang-tidy/checks/readability-redundant-preprocessor.rst
new file mode 100644
index 000000000000..f013a3417d3b
--- /dev/null
+++ b/clang-tools-extra/docs/clang-tidy/checks/readability-redundant-preprocessor.rst
@@ -0,0 +1,61 @@
+.. title:: clang-tidy - readability-redundant-preprocessor
+
+readability-redundant-preprocessor
+==================================
+
+Finds potentially redundant preprocessor directives. At the moment the
+following cases are detected:
+
+* `#ifdef` .. `#endif` pairs which are nested inside an outer pair with the
+  same condition. For example:
+
+.. code-block:: c++
+
+  #ifdef FOO
+  #ifdef FOO // inner ifdef is considered redundant
+  void f();
+  #endif
+  #endif
+
+* Same for `#ifndef` .. `#endif` pairs. For example:
+
+.. code-block:: c++
+
+  #ifndef FOO
+  #ifndef FOO // inner ifndef is considered redundant
+  void f();
+  #endif
+  #endif
+
+* `#ifndef` inside an `#ifdef` with the same condition:
+
+.. code-block:: c++
+
+  #ifdef FOO
+  #ifndef FOO // inner ifndef is considered redundant
+  void f();
+  #endif
+  #endif
+
+* `#ifdef` inside an `#ifndef` with the same condition:
+
+.. code-block:: c++
+
+  #ifndef FOO
+  #ifdef FOO // inner ifdef is considered redundant
+  void f();
+  #endif
+  #endif
+
+* `#if` .. `#endif` pairs which are nested inside an outer pair with the same
+  condition. For example:
+
+.. code-block:: c++
+
+  #define FOO 4
+  #if FOO == 4
+  #if FOO == 4 // inner if is considered redundant
+  void f();
+  #endif
+  #endif
+
diff --git a/clang-tools-extra/test/clang-tidy/readability-redundant-preprocessor-ifdef.cpp b/clang-tools-extra/test/clang-tidy/readability-redundant-preprocessor-ifdef.cpp
new file mode 100644
index 000000000000..72b608b1c2c0
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/readability-redundant-preprocessor-ifdef.cpp
@@ -0,0 +1,36 @@
+// RUN: %check_clang_tidy %s readability-redundant-preprocessor %t -- -- -DFOO
+
+// Positive testing.
+#ifdef FOO
+// CHECK-NOTES: [[@LINE+1]]:2: warning: nested redundant #ifdef; consider removing it [readability-redundant-preprocessor]
+#ifdef FOO
+// CHECK-NOTES: [[@LINE-3]]:2: note: previous #ifdef was here
+void f();
+#endif
+#endif
+
+// Positive testing of inverted condition.
+#ifdef FOO
+// CHECK-NOTES: [[@LINE+1]]:2: warning: nested redundant #ifndef; consider removing it [readability-redundant-preprocessor]
+#ifndef FOO
+// CHECK-NOTES: [[@LINE-3]]:2: note: previous #ifdef was here
+void f2();
+#endif
+#endif
+
+// Negative testing.
+#ifdef BAR
+void g();
+#endif
+
+#ifdef FOO
+#ifdef BAR
+void h();
+#endif
+#endif
+
+#ifdef FOO
+#ifndef BAR
+void i();
+#endif
+#endif
diff --git a/clang-tools-extra/test/clang-tidy/readability-redundant-preprocessor.cpp b/clang-tools-extra/test/clang-tidy/readability-redundant-preprocessor.cpp
new file mode 100644
index 000000000000..6cffd8f43899
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/readability-redundant-preprocessor.cpp
@@ -0,0 +1,84 @@
+// RUN: %check_clang_tidy %s readability-redundant-preprocessor %t -- -- -I %S
+
+// Positive testing.
+#ifndef FOO
+// CHECK-NOTES: [[@LINE+1]]:2: warning: nested redundant #ifndef; consider removing it [readability-redundant-preprocessor]
+#ifndef FOO
+// CHECK-NOTES: [[@LINE-3]]:2: note: previous #ifndef was here
+void f();
+#endif
+#endif
+
+// Positive testing of inverted condition.
+#ifndef FOO
+// CHECK-NOTES: [[@LINE+1]]:2: warning: nested redundant #ifdef; consider removing it [readability-redundant-preprocessor]
+#ifdef FOO
+// CHECK-NOTES: [[@LINE-3]]:2: note: previous #ifndef was here
+void f2();
+#endif
+#endif
+
+// Negative testing.
+#include "readability-redundant-preprocessor.h"
+
+#ifndef BAR
+void g();
+#endif
+
+#ifndef FOO
+#ifndef BAR
+void h();
+#endif
+#endif
+
+#ifndef FOO
+#ifdef BAR
+void i();
+#endif
+#endif
+
+// Positive #if testing.
+#define FOO 4
+
+#if FOO == 4
+// CHECK-NOTES: [[@LINE+1]]:2: warning: nested redundant #if; consider removing it [readability-redundant-preprocessor]
+#if FOO == 4
+// CHECK-NOTES: [[@LINE-3]]:2: note: previous #if was here
+void j();
+#endif
+#endif
+
+#if FOO == 3 + 1
+// CHECK-NOTES: [[@LINE+1]]:2: warning: nested redundant #if; consider removing it [readability-redundant-preprocessor]
+#if FOO == 3 + 1
+// CHECK-NOTES: [[@LINE-3]]:2: note: previous #if was here
+void j();
+#endif
+#endif
+
+#if FOO == \
+    4
+// CHECK-NOTES: [[@LINE+1]]:2: warning: nested redundant #if; consider removing it [readability-redundant-preprocessor]
+#if FOO == \
+    4
+// CHECK-NOTES: [[@LINE-5]]:2: note: previous #if was here
+void j();
+#endif
+#endif
+
+// Negative #if testing.
+#define BAR 4
+
+#if FOO == 4
+#if BAR == 4
+void k();
+#endif
+#endif
+
+#if FOO == \
+    4
+#if BAR == \
+    5
+void k();
+#endif
+#endif
diff --git a/clang-tools-extra/test/clang-tidy/readability-redundant-preprocessor.h b/clang-tools-extra/test/clang-tidy/readability-redundant-preprocessor.h
new file mode 100644
index 000000000000..dfe5f9733afb
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/readability-redundant-preprocessor.h
@@ -0,0 +1,5 @@
+#ifndef FOO
+#ifndef FOO // this would warn, but not in a header
+void f();
+#endif
+#endif