[clang-tidy] As a simple heuristic don't emit a swap fixit that would create

negative-sized memsets.

memset(x, -1, 0) is still useless but swapping makes no sense here. Just emit
a warning.

llvm-svn: 213157

1 files changed, 2 insertions, 1 deletions

diff --git a/clang-tools-extra/clang-tidy/google/MemsetZeroLengthCheck.cpp b/clang-tools-extra/clang-tidy/google/MemsetZeroLengthCheck.cpp
index 98c6246b836..b9b776e0b5c 100644
--- a/clang-tools-extra/clang-tidy/google/MemsetZeroLengthCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/MemsetZeroLengthCheck.cpp
@@ -63,7 +63,8 @@ void MemsetZeroLengthCheck::check(const MatchFinder::MatchResult &Result) {
     return;
 
   // If both arguments evaluate to zero emit a warning without fix suggestions.
-  if (Arg1->EvaluateAsInt(Value1, *Result.Context) && Value1 == 0) {
+  if (Arg1->EvaluateAsInt(Value1, *Result.Context) &&
+      (Value1 == 0 || Value1.isNegative())) {
     diag(Call->getLocStart(), "memset of size zero");
     return;
   }