r337706 - [Sema] Don't emit -Wmemset-transposed-args for memset(p, 0, 0)

[Erik Pilkington via cfe-commits]

Author: epilk
Date: Mon Jul 23 09:24:14 2018
New Revision: 337706

URL: http://llvm.org/viewvc/llvm-project?rev=337706&view=rev
Log:
[Sema] Don't emit -Wmemset-transposed-args for memset(p,0,0)

Thanks to Arthur O'Dwyer for the suggestion!

Modified:
    cfe/trunk/lib/Sema/SemaChecking.cpp
    cfe/trunk/test/Sema/transpose-memset.c

Modified: cfe/trunk/lib/Sema/SemaChecking.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaChecking.cpp?rev=337706&r1=337705&r2=337706&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaChecking.cpp (original)
+++ cfe/trunk/lib/Sema/SemaChecking.cpp Mon Jul 23 09:24:14 2018
@@ -8788,11 +8788,14 @@ static void CheckMemaccessSize(Sema &S,
   const Expr *SizeArg =
     Call->getArg(BId == Builtin::BImemset ? 2 : 1)->IgnoreImpCasts();
 
+  auto isLiteralZero = [](const Expr *E) {
+    return isa<IntegerLiteral>(E) && cast<IntegerLiteral>(E)->getValue() == 0;
+  };
+
   // If we're memsetting or bzeroing 0 bytes, then this is likely an error.
   SourceLocation CallLoc = Call->getRParenLoc();
   SourceManager &SM = S.getSourceManager();
-  if (isa<IntegerLiteral>(SizeArg) &&
-      cast<IntegerLiteral>(SizeArg)->getValue() == 0 &&
+  if (isLiteralZero(SizeArg) &&
       !isArgumentExpandedFromMacro(SM, CallLoc, SizeArg->getExprLoc())) {
 
     SourceLocation DiagLoc = SizeArg->getExprLoc();
@@ -8804,7 +8807,7 @@ static void CheckMemaccessSize(Sema &S,
                                     CallLoc, SM, S.getLangOpts()) == "bzero")) {
       S.Diag(DiagLoc, diag::warn_suspicious_bzero_size);
       S.Diag(DiagLoc, diag::note_suspicious_bzero_size_silence);
-    } else {
+    } else if (!isLiteralZero(Call->getArg(1)->IgnoreImpCasts())) {
       S.Diag(DiagLoc, diag::warn_suspicious_sizeof_memset) << 0;
       S.Diag(DiagLoc, diag::note_suspicious_sizeof_memset_silence) << 0;
     }

Modified: cfe/trunk/test/Sema/transpose-memset.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/transpose-memset.c?rev=337706&r1=337705&r2=337706&view=diff
==============================================================================
--- cfe/trunk/test/Sema/transpose-memset.c (original)
+++ cfe/trunk/test/Sema/transpose-memset.c Mon Jul 23 09:24:14 2018
@@ -22,6 +22,7 @@ int main() {
   memset(array, (int)sizeof(array), (0)); // no warning
   memset(array, (int)sizeof(array), 32); // no warning
   memset(array, 32, (0)); // no warning
+  memset(array, 0, 0); // no warning
 
   bzero(ptr, 0); // expected-warning{{'size' argument to bzero is '0'}} expected-note{{parenthesize the second argument to silence}}
   real_bzero(ptr, 0); // expected-warning{{'size' argument to bzero is '0'}} expected-note{{parenthesize the second argument to silence}}
@@ -55,6 +56,6 @@ void macros() {
 
   __builtin_memset(array, 0, ZERO); // no warning
   __builtin_bzero(array, ZERO);
-  __builtin_memset(array, 0, 0); // expected-warning{{'size' argument to memset}} // expected-note{{parenthesize}}
+  __builtin_memset(array, 1, 0); // expected-warning{{'size' argument to memset}} // expected-note{{parenthesize}}
   __builtin_bzero(array, 0); // expected-warning{{'size' argument to bzero}} // expected-note{{parenthesize}}
 }