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From: Andres Freund <[email protected]>
To: Bertrand Drouvot <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: Peter Eisentraut <[email protected]>
Cc: [email protected]
Subject: Re: Defend against -ffast-math in meson builds
Date: Wed, 11 Mar 2026 14:10:54 -0400
Message-ID: <vjpqvlolycvkc3k6elcb3wchf7mjg6bn5ek7b352cvsnq77qln@nnjpkw3cykly> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<vwnxbsap65km373ghtqhhvhwnc35suwraegb7z5op4okxyuwzu@kpaumampogpe>
	<[email protected]>
	<[email protected]>
	<abGPko4lPv/[email protected]>
	<[email protected]>
	<[email protected]>

Hi,

On 2026-03-11 17:54:33 +0000, Bertrand Drouvot wrote:
> > But maybe we should move the
> > code-level tests out of the datetime files and into utils/float.h
> > or some such place.
> 
> But still, I'm not sure the code-level guard is enough for meson. I think we
> need to put a guard in meson.build for the "oddity" described in [1]:

I think you rather need to get to the bottom of that issue.


> it compiles fine with CFLAGS="-ffast-math" CC="gcc" meson setup meson_build but
> produces issues during the regression tests.

This fails to build here as expected.

Are you sure that you actually specified it during meson setup and then didn't
reconfigure while the CFLAGs aren't specified?


> I just had a closer look and it looks like that the reason is that it's being
> added at link time:
> 
> $ cat meson_build/build.ninja | grep LINK_ARGS | grep -c "ffast-math"
> 254

It's added to both, compile and link args, afaict?

andres@awork3:/tmp/pg-fast-math$ grep ffast-math build.ninja |awk '{print $1}'|sort|uniq -c
   1679 ARGS
    255 LINK_ARGS

Greetings,

Andres Freund





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