Re: NULL passed as an argument to memcmp() in parse_func.c

On Mon, Jun 22, 2015 at 2:55 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Piotr Stefaniak <postgres@piotr-stefaniak.me> writes:
>> There are two places in parse_func.c where memcmp() conditionally gets a
>> NULL as its first argument, which invokes undefined behavior. I guess
>> gcc -O2 will make some assumptions based on memcpy's __nonnull attribute.
>
> 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.  Are
> you seeing any observable problem here, and if so what is it?

I dunno, this seems like playing with fire to me.  A null-test would
be pretty cheap insurance.

-- 
Robert Haas
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