[cfe-commits] [PATCH] Properly check for unused comparisons in arguments to function-like macros

[Matt Beaumont-Gay]

Hi chandlerc,

Tweaking the implementation of -Wunused-value, I noticed a misbehavior of -Wunused-comparison: If the comparison is in a macro argument, we give up on emitting -Wunused-comparison, but fall through to emitting -Wunused-value. This patch fixes -Wunused-comparison to do the right thing. I also added a helper function 'isMacroBodyExpansion' to SourceManager (to go along with 'isMacroArgExpansion').

http://llvm-reviews.chandlerc.com/D259

Files:
  include/clang/Basic/SourceManager.h
  lib/Basic/SourceManager.cpp
  lib/Sema/SemaStmt.cpp
  test/Sema/unused-expr-system-header.c

Index: include/clang/Basic/SourceManager.h
===================================================================
--- include/clang/Basic/SourceManager.h
+++ include/clang/Basic/SourceManager.h
@@ -329,6 +329,11 @@
         SourceLocation::getFromRawEncoding(ExpansionLocEnd).isInvalid();
     }
 
+    bool isMacroBodyExpansion() const {
+      return getExpansionLocStart().isValid() &&
+        SourceLocation::getFromRawEncoding(ExpansionLocEnd).isValid();
+    }
+
     bool isFunctionMacroExpansion() const {
       return getExpansionLocStart().isValid() &&
           getExpansionLocStart() != getExpansionLocEnd();
@@ -1126,6 +1131,11 @@
   /// expanded.
   bool isMacroArgExpansion(SourceLocation Loc) const;
 
+  /// \brief Tests whether the given source location represents the expansion of
+  /// a macro body (as opposed to an expansion of the argument to a
+  /// function-like macro).
+  bool isMacroBodyExpansion(SourceLocation Loc) const;
+
   /// \brief Returns true if \p Loc is inside the [\p Start, +\p Length)
   /// chunk of the source location address space.
   ///
Index: lib/Basic/SourceManager.cpp
===================================================================
--- lib/Basic/SourceManager.cpp
+++ lib/Basic/SourceManager.cpp
@@ -979,6 +979,15 @@
   return Expansion.isMacroArgExpansion();
 }
 
+bool SourceManager::isMacroBodyExpansion(SourceLocation Loc) const {
+  if (!Loc.isMacroID()) return false;
+
+  FileID FID = getFileID(Loc);
+  const SrcMgr::SLocEntry *E = &getSLocEntry(FID);
+  const SrcMgr::ExpansionInfo &Expansion = E->getExpansion();
+  return Expansion.isMacroBodyExpansion();
+}
+
 
 //===----------------------------------------------------------------------===//
 // Queries about the code at a SourceLocation.
Index: lib/Sema/SemaStmt.cpp
===================================================================
--- lib/Sema/SemaStmt.cpp
+++ lib/Sema/SemaStmt.cpp
@@ -125,7 +125,7 @@
 
   // Suppress warnings when the operator, suspicious as it may be, comes from
   // a macro expansion.
-  if (Loc.isMacroID())
+  if (S.SourceMgr.isMacroBodyExpansion(Loc))
     return false;
 
   S.Diag(Loc, diag::warn_unused_comparison)
Index: test/Sema/unused-expr-system-header.c
===================================================================
--- test/Sema/unused-expr-system-header.c
+++ test/Sema/unused-expr-system-header.c
@@ -3,8 +3,10 @@
 void f(int i1, int i2) {
   POSSIBLY_BAD_MACRO(5);
   STATEMENT_EXPR_MACRO(5);
-  COMMA_MACRO_1(i1 == i2, f(i1, i2)); // expected-warning {{expression result unused}}
+  COMMA_MACRO_1(i1 == i2, f(i1, i2)); // expected-warning {{comparison result unused}} \
+                                      // expected-note {{equality comparison}}
   COMMA_MACRO_2(i1 == i2, f(i1, i2));
-  COMMA_MACRO_3(i1 == i2, f(i1, i2)); // expected-warning {{expression result unused}}
+  COMMA_MACRO_3(i1 == i2, f(i1, i2)); // expected-warning {{comparison result unused}} \
+                                      // expected-note {{equality comparison}}
   COMMA_MACRO_4(i1 == i2, f(i1, i2));
 }
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