Horton

Re: Expand palloc/pg_malloc API

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Cc: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2022-10-11T16:04:20Z
Lists: pgsql-hackers 
Peter Eisentraut <peter.eisentraut@enterprisedb.com> writes:
> On 14.09.22 06:53, Tom Lane wrote:
>> 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?

Hmm ... the individual allocators have that info, but mcxt.c doesn't
have access to it.  I guess we could invent an additional "method"
to return the requested size of a chunk, which is only available in
MEMORY_CONTEXT_CHECKING builds, or maybe in !MEMORY_CONTEXT_CHECKING
it returns the allocated size instead.

			regards, tom lane

Commits

  1. Add repalloc0 and repalloc0_array

  2. Expand palloc/pg_malloc API for more type safety

  3. Assorted examples of expanded type-safer palloc/pg_malloc API