[PATCH] D49112: [Sema] Implement -Wmemset-transposed-args

[Arthur O'Dwyer via Phabricator via cfe-commits]

Quuxplusone added inline comments.


================
Comment at: clang/include/clang/Basic/DiagnosticSemaKinds.td:662
+def note_suspicious_sizeof_memset_silence : Note<
+  "%select{parenthesize the third argument|cast the second argument to 'int'}0 to silence">;
+
----------------
If it were my codebase, I'd rather see a cast to `(unsigned char)` than a cast to `(int)`. (The second argument to memset is supposed to be a single byte.) Why did you pick `(int)` specifically?


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Comment at: clang/lib/Sema/SemaChecking.cpp:7962
+  if (auto *BO = dyn_cast<BinaryOperator>(SizeofExpr)) {
+    if (BO->getOpcode() != BO_Mul)
+      return false;
----------------
Honestly, if the second argument to `memset` involves `sizeof` *at all*, it's probably a bug, isn't it?

    memset(&buf, sizeof foo + 10, 0xff);
    memset(&buf, sizeof foo * sizeof bar, 0xff);

Should Clang really go out of its way to silence the warning in these cases?


Repository:
  rC Clang

https://reviews.llvm.org/D49112