Suppress -Warray-bounds in certain cases involving macros from system headers.

The motivation here is a "clever" implementation of strncmp(), which peels the first few comparisons via chained conditional expressions which ensure that the input arrays are known at compile time to be sufficiently large.

llvm-svn: 146430

1 files changed, 11 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 1c93931b5c1..bb567d0986a 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -4275,7 +4275,7 @@ static bool IsTailPaddedMemberArray(Sema &S, llvm::APInt Size,
 
 void Sema::CheckArrayAccess(const Expr *BaseExpr, const Expr *IndexExpr,
                             bool isSubscript, bool AllowOnePastEnd) {
-  const Type* EffectiveType = getElementType(BaseExpr);
+  const Type *EffectiveType = getElementType(BaseExpr);
   BaseExpr = BaseExpr->IgnoreParenCasts();
   IndexExpr = IndexExpr->IgnoreParenCasts();
 
@@ -4381,6 +4381,16 @@ void Sema::CheckArrayAccess(const Expr *expr) {
     switch (expr->getStmtClass()) {
       case Stmt::ArraySubscriptExprClass: {
         const ArraySubscriptExpr *ASE = cast<ArraySubscriptExpr>(expr);
+        // Suppress the warning if the subscript expression (as identified by
+        // the ']' location) and the index expression are both from macro
+        // expansions within a system header.
+        SourceLocation RBracketLoc = SourceMgr.getSpellingLoc(
+            ASE->getRBracketLoc());
+        SourceLocation IndexLoc = SourceMgr.getSpellingLoc(
+            ASE->getIdx()->IgnoreParens()->getLocStart());
+        if (SourceMgr.isFromSameFile(RBracketLoc, IndexLoc) &&
+            SourceMgr.isInSystemHeader(RBracketLoc))
+          return;
         CheckArrayAccess(ASE->getBase(), ASE->getIdx(), true,
                          AllowOnePastEnd > 0);
         return;