Horton

Re: Fix and improve allocation formulas

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andres Freund <andres@anarazel.de>, Bertrand Drouvot <bertranddrouvot.pg@gmail.com>, pgsql-hackers@lists.postgresql.org
Date: 2025-12-12T09:53:32Z
Lists: pgsql-hackers

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  1. btree_gist: Fix memory allocation formula

On Thu, Dec 11, 2025 at 11:43:27AM -0500, Tom Lane wrote:
> And before that, you'd have to get consensus that sizeof(*var) *is*
> the preferred style.  I for one don't like it a bit.  IMO what it
> mostly accomplishes is to remove a cue as to what we are allocating.
> I don't agree that it removes a chance for error, either.  Sure,
> if you write
> 
> 	foo = palloc(sizeof(typeA))
> 
> when foo is of type typeB*, you made a mistake --- but we know how
> to get the compiler to warn about such mistakes, and indeed the
> main point of the palloc_object() changes was to catch those.
> However, suppose you write
> 
> 	foo = palloc(sizeof(*bar))
> 
> I claim that's about an equally credible typo, and there is
> nothing that will detect it.

Yeah, I'd prefer something where we keep track of the type, with the
extra layer that enforces a cast to the type of the variable like
palloc_object/array macros.  The latter style of specifying a variable
pointer within the sizeof is more error-prone long-term, so it's not
something I think we should encourage.
--
Michael