erik.pilkington 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">;
+
----------------
Quuxplusone wrote:
> 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?
I chose `int` because that's the actual type of the second parameter to
`memset`, it just gets casted down to `unsigned char` internally. FWIW, either
type will suppress the warning. I'm fine with recommending `unsigned char` if
you have a strong preference for it.
================
Comment at: clang/lib/Sema/SemaChecking.cpp:7962
+ if (auto *BO = dyn_cast<BinaryOperator>(SizeofExpr)) {
+ if (BO->getOpcode() != BO_Mul)
+ return false;
----------------
Quuxplusone wrote:
> 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?
Sure, that seems reasonable. The new patch makes this check less conservative.
https://reviews.llvm.org/D49112
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