Re: Expand palloc/pg_malloc API

On 14.09.22 06:53, Tom Lane wrote:
> I wrote:
>> It kind of feels that the argument order should be pointer, oldsize, size.
>> It feels even more strongly that people will get the ordering wrong,
>> whichever we choose.  Is there a way to make that more bulletproof?
> 
> Actually ... an even-more-terrifyingly-plausible misuse is that the
> supplied oldsize is different from the actual previous allocation.
> We should try to check that.  In MEMORY_CONTEXT_CHECKING builds
> it should be possible to assert that oldsize == requested_size.
> We don't have that data if !MEMORY_CONTEXT_CHECKING, but we could
> at least assert that oldsize <= allocated chunk size.

I'm not very familiar with MEMORY_CONTEXT_CHECKING.  Where would one get 
these values?