Re: [Outreachy] Return value before or after free()?

On 2020-01-07 at 01:08:09, brian m. carlson wrote:

Unfortunately, compilers have gotten much more aggressive about assuming
that undefined behavior never occurs and rewriting code based on that.
clang is not as bad about doing that, but GCC is very aggressive about
it.  There are multiple instances where NULL pointer checks have been
optimized out because the compiler exploited undefined behavior to
assume a pointer was never NULL.

In this case, the only case in which we can safely assume that this
behavior is acceptable is that r is NULL, in which case C11 tells us
that "no action occurs" due to the free. So the compiler could just
optimize this out to a "return 0".  Just because it doesn't now doesn't
mean we can assume it won't in the future, so we do need to fix this.

I'll send a patch.

Oof, I just realized that you had tagged this with "[Outreachy]", which
means that you were probably planning on sending a patch to fix this,
and then I went and did it instead, so let me apologize for doing that.

I sent it because oftentimes we say "we should fix this thing" and then
never do it because nobody sends a patch, but in this case I should have
paid more attention and waited for you to respond and send one instead.

Again, sorry about that.
-- 
brian m. carlson: Houston, Texas, US
OpenPGP: https://keybase.io/bk2204