turn down the logical bitwise confusion warning to not warn

when the RHS of the ||/&& is ever 0 or 1.  This handles a variety of
creative idioms for "true" used in C programs and fixes many false 
positives at the expense of a few false negatives.  This fixes
rdar://8230351.

llvm-svn: 109314

1 files changed, 14 insertions, 11 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 8b2e0203b38..5281f3ff793 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -5819,18 +5819,21 @@ inline QualType Sema::CheckLogicalOperands( // C99 6.5.[13,14]
   // bitwise one.  We do this when the LHS is a non-bool integer and the RHS
   // is a constant.
   if (lex->getType()->isIntegerType() && !lex->getType()->isBooleanType() &&
-      rex->getType()->isIntegerType() && rex->isEvaluatable(Context) &&
-      // Don't warn if the RHS is a (constant folded) boolean expression like
-      // "sizeof(int) == 4".
-      !rex->isKnownToHaveBooleanValue() &&
+      rex->getType()->isIntegerType() &&
       // Don't warn in macros.
-      !Loc.isMacroID())
-    Diag(Loc, diag::warn_logical_instead_of_bitwise)
-     << rex->getSourceRange()
-      << (Opc == BinaryOperator::LAnd ? "&&" : "||")
-      << (Opc == BinaryOperator::LAnd ? "&" : "|");
-  
-  
+      !Loc.isMacroID()) {
+    // If the RHS can be constant folded, and if it constant folds to something
+    // that isn't 0 or 1 (which indicate a potential logical operation that
+    // happened to fold to true/false) then warn.
+    Expr::EvalResult Result;
+    if (rex->Evaluate(Result, Context) && !Result.HasSideEffects &&
+        Result.Val.getInt() != 0 && Result.Val.getInt() != 1) {
+      Diag(Loc, diag::warn_logical_instead_of_bitwise)
+       << rex->getSourceRange()
+        << (Opc == BinaryOperator::LAnd ? "&&" : "||")
+        << (Opc == BinaryOperator::LAnd ? "&" : "|");
+    }
+  }
   
   if (!Context.getLangOptions().CPlusPlus) {
     UsualUnaryConversions(lex);