Fix <rdar://problem/6703892> by not warning about self-comparisons of enum

constants.

llvm-svn: 67390

2 files changed, 13 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index c06f1cfad78..705fe4dfeef 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -3276,11 +3276,15 @@ QualType Sema::CheckCompareOperands(Expr *&lex, Expr *&rex, SourceLocation Loc,
     // For non-floating point types, check for self-comparisons of the form
     // x == x, x != x, x < x, etc.  These always evaluate to a constant, and
     // often indicate logic errors in the program.
+    // NOTE: Per <rdar://problem/6703892>, don't warn about comparisons of enum
+    //  constants.  These can arise from macro expansions, and are usually quite
+    //  deliberate.
     Expr *LHSStripped = lex->IgnoreParens();
     Expr *RHSStripped = rex->IgnoreParens();
     if (DeclRefExpr* DRL = dyn_cast<DeclRefExpr>(LHSStripped))
       if (DeclRefExpr* DRR = dyn_cast<DeclRefExpr>(RHSStripped))
-        if (DRL->getDecl() == DRR->getDecl())
+        if (DRL->getDecl() == DRR->getDecl() &&
+            !isa<EnumConstantDecl>(DRL->getDecl()))
           Diag(Loc, diag::warn_selfcomparison);
     
     if (isa<CastExpr>(LHSStripped))
diff --git a/clang/test/Sema/self-comparison.c b/clang/test/Sema/self-comparison.c
index 023afb7926f..8bf54fde9f5 100644
--- a/clang/test/Sema/self-comparison.c
+++ b/clang/test/Sema/self-comparison.c
@@ -23,3 +23,11 @@ int bar(float x) {
 int bar2(float x) {
   return x != x; // no-warning
 }
+
+// Motivated by <rdar://problem/6703892>, self-comparisons of enum constants
+// should not be warned about.  These can be expanded from macros, and thus
+// are usually deliberate.
+int compare_enum() {
+  enum { A };
+  return A == A; // no-warning
+}