On Mon, Dec 5, 2022 at 3:12 PM Marco Elver <elver@xxxxxxxxxx> wrote:
On Mon, 5 Dec 2022 at 14:26, Alexander Potapenko <glider@xxxxxxxxxx> wrote:
>
> Recent Clang changes may cause it to delete calls of memcpy(), if the
> source is an uninitialized volatile local.
> This happens because passing a pointer to a volatile local into memcpy()
> discards the volatile qualifier, giving the compiler a free hand to
> optimize the memcpy() call away.
>
> To outsmart the compiler, we call __msan_memcpy() instead of memcpy()
> in test_memcpy_aligned_to_aligned(), test_memcpy_aligned_to_unaligned()
> and test_memcpy_aligned_to_unaligned2(), because it's the behavior of
> __msan_memcpy() we are testing here anyway.
>
> Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
It might be nice to retain memcpy() calls somehow, as that tests
end-to-end that the compiler does the right thing here i.e. replacing
the memcpy() calls with instrumented versions.
Does OPTIMIZER_HIDE_VAR() help? This should prevent the compiler from
seeing it's uninitialized.
It indeed does, thanks!
Let me send a v2.
