tree 272c35e2c2b6828e251bd4910407024736c4cf67
parent 209717796747895be7a1d0454e850aeebed94a8f
author David Benjamin <davidben@google.com> 1716297458 +0000
committer Dawn LUCI CQ <dawn-scoped@luci-project-accounts.iam.gserviceaccount.com> 1716297458 +0000

Don't memcpy zero bytes in generated WireCmd.cpp

Due to a C language bug, memcpy is undefined on empty inputs when the
pointers are NULL. See https://davidben.net/2024/01/15/empty-slices.html
for details. This code triggers UBSan bugs like the following:

https://luci-milo.appspot.com/ui/inv/build-8749056521619502353/test-results?q=WebGPUSwapBufferProviderTest.ReuseSwapBuffers&sortby=&groupby=

For most of these in Chromium, I've been fixing them to use spans, or at
least std::copy and std::copy_n, which do not have this language bug and
are specialized as memcpy when the type is trivially copyable. However,
when I tried to do that, I ran into issues with WGPUColor and
WGPUColorTransfer being different types. There's a lot of synthesized
code here I can't follow so, instead, just guard the memcpy with a zero
check to fix the undefined behavior.

Bug: chromium:40248746
Change-Id: I4041bfb750a3e0fcf56353bffefc0a2715603475
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/188900
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Auto-Submit: David Benjamin <davidben@google.com>