commit d69ff70c0b3dc1922d5d486b84f27b51820c43cf
author Benjamin Kramer <benny.kra@googlemail.com> Wed Jul 16 14:52:07 2014 +0000
committer Copybara-Service <copybara-worker@google.com> Fri Sep 04 12:59:36 2020 -0700
tree df419f2379953f89eb56d3dca6928f4db5a93738
parent bf8f3328322d1c75344d5bc2aae830f07597a698

[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
GitOrigin-RevId: 806bcabcdafbb1deb8e3f1821d848f33f67a8dd5

clang-tidy/google/MemsetZeroLengthCheck.cpp

diff --git a/clang-tidy/google/MemsetZeroLengthCheck.cpp b/clang-tidy/google/MemsetZeroLengthCheck.cpp
index 98c6246..b9b776e 100644
--- a/clang-tidy/google/MemsetZeroLengthCheck.cpp
+++ b/clang-tidy/google/MemsetZeroLengthCheck.cpp
@@ -63,7 +63,8 @@
     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;
   }

test/clang-tidy/google-memset-zero-length.cpp

diff --git a/test/clang-tidy/google-memset-zero-length.cpp b/test/clang-tidy/google-memset-zero-length.cpp
index 5b23271..b5393bd 100644
--- a/test/clang-tidy/google-memset-zero-length.cpp
+++ b/test/clang-tidy/google-memset-zero-length.cpp
@@ -49,5 +49,9 @@
 // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: memset of size zero
 // CHECK-FIXES: memset(a, v, 0);
 
+  memset(a, -1, v);
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: memset of size zero
+// CHECK-FIXES: memset(a, -1, v);
+
   memtmpl<0>();
 }