On 06/22/2015 08:55 PM, Tom Lane wrote:
> Are you seeing any observable problem here, and if so what is it?
Not yet; perhaps with GCC 7 or 8...
> If I recall that code correctly, the assumption was that if the third
> argument is zero then memcmp() must not fetch any bytes (not should not,
> but MUST not) and therefore it doesn't matter if we pass a NULL.
It's not about fetching any bytes, it's about passing an invalid pointer
(a null pointer in this case) which gives a compiler the opportunity to
apply an optimization. For example, glibc has memcpy marked as
__nonnull(1,2).
But if you remain unconvinced then I yield.
