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Date: Wed, 13 Mar 2024 00:43:11 -0500
Message-Id: <CZSDSNYEUHUL.399XLPGCJSJ5H@neon.tech>
Cc: <michael@paquier.xyz>, <pgsql-hackers@postgresql.org>
Subject: Re: meson: Specify -Wformat as a common warning flag for extensions
To: "Sutou Kouhei" <kou@clear-code.com>
From: "Tristan Partin" <tristan@neon.tech>
References: <CZO4L8L0KP7K.1RWJWEAGL8UMN@neon.tech>
 <Zeqw9vGrYlb250aO@paquier.xyz> <CZOHWDYQJQCQ.23A5RRV1E05N2@neon.tech>
 <20240313.085638.207599003452490069.kou@clear-code.com>
In-Reply-To: <20240313.085638.207599003452490069.kou@clear-code.com>
Archived-At: <https://www.postgresql.org/message-id/CZSDSNYEUHUL.399XLPGCJSJ5H%40neon.tech>
Precedence: bulk

On Tue Mar 12, 2024 at 6:56 PM CDT, Sutou Kouhei wrote:
> Hi,
>
> In <CZOHWDYQJQCQ.23A5RRV1E05N2@neon.tech>
>   "Re: meson: Specify -Wformat as a common warning flag for extensions" o=
n Fri, 08 Mar 2024 10:05:27 -0600,
>   "Tristan Partin" <tristan@neon.tech> wrote:
>
> > Ok, I figured this out. -Wall implies -Wformat=3D1. We set warning_leve=
l
> > to 1 in the Meson project() call, which implies -Wall, and set -Wall
> > in CFLAGS for autoconf. That's the reason we don't get issues building
> > Postgres. A user making use of the pg_config --cflags option, as Sutou
> > is, *will* run into the aforementioned issues, since we don't
> > propogate -Wall into pg_config.
> >=20
> > 	$ gcc $(pg_config --cflags) -E - < /dev/null > /dev/null
> > 	cc1: warning: =E2=80=98-Wformat-security=E2=80=99 ignored without =E2=
=80=98-Wformat=E2=80=99
> > 	[-Wformat-security]
> > 	$ gcc -Wall $(pg_config --cflags) -E - < /dev/null > /dev/null
> > 	(nothing printed)
>
> Thanks for explaining this. You're right. This is the reason
> why we don't need this for PostgreSQL itself but we need
> this for PostgreSQL extensions. Sorry. I should have
> explained this in the first e-mail...
>
>
> What should we do to proceed this patch?

Perhaps adding some more clarification in the comments that I wrote.

-  # -Wformat-security requires -Wformat, so check for it
+  # -Wformat-secuirty requires -Wformat. We compile with -Wall in=20
+  # Postgres, which includes -Wformat=3D1. -Wformat is shorthand for=20
+  # -Wformat=3D1. The set of flags which includes -Wformat-security is=20
+  # persisted into pg_config --cflags, which is commonly used by=20
+  # PGXS-based extensions. The lack of -Wformat in the persisted flags
+  # will produce a warning on many GCC versions, so even though adding=20
+  # -Wformat here is a no-op for Postgres, it silences other use cases.

That might be too long-winded though :).

--=20
Tristan Partin
Neon (https://neon.tech)