Re: Adding REPACK [concurrently]

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Antonin Houska <ah(at)cybertec(dot)at>
Cc: Tomas Vondra <tomas(at)vondra(dot)me>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, vignesh C <vignesh21(at)gmail(dot)com>, Srinath Reddy Sadipiralla <srinath2133(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Mihail Nikalayeu <mihailnikalayeu(at)gmail(dot)com>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Robert Treat <rob(at)xzilla(dot)net>
Subject: Re: Adding REPACK [concurrently]
Date: 2026-04-08 16:47:33
Message-ID: 3074023.1775666853@sss.pgh.pa.us
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Antonin Houska <ah(at)cybertec(dot)at> writes:
> Tomas Vondra <tomas(at)vondra(dot)me> wrote:
>> while building on a rpi5 with a 32-bit system, I'm getting these warnings:
>> ...
>> I'm not sure if it's just the compiler (gcc 14.2) being pesky, or if
>> it's an actual issue. The repack tests seem to pass fine.

Several 32-bit BF animals are showing these too (so far: dodo,
grison, and turaco).

> We already introduced this definition above in the function to suppress this
> kind of warning

> union
> {
> alignas(int32) varlena hdr;
> char data[sizeof(void *)];
> } chunk_header;

> The problem on a 32-bit system probably is that sizeof(void *) is 4. We need
> some other constant. Maybe (sizeof(varlena) + 1) ...

This seems unnecessarily Rube Goldberg-ish already. Why not just

uint64 chunk_header;

It will not hurt anything if the variable has more-than-required
alignment. And it'd be better if it were the same size everywhere.

regards, tom lane

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