Re: [ulogd2 PATCH 03/10] build: use pkg-config or upstream M4 for mysql

[Jeremy Sowden <jeremy@azazel.net>]

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On 2022-01-06, at 23:15:31 +0100, Jan Engelhardt wrote:
> On Thursday 2022-01-06 22:09, Jeremy Sowden wrote:
>
> >Recent versions of mariadb and mysql have supported pkg-config.
>
> (This made me read up on Stackexchange about exact rules for present
> perfect, only to find it is not neatly delineated.) IMO better to
> just use present. They (still) support pkg-config.

Agreed.

> >+  dnl Recent versions of MySQL and MariaDB have included pkg-config support.
> >+  dnl Older versions have included an mysql.m4 file which provides macros to
>
> "had included", as I don't see that m4 file anymore on my (mariadb) systems.
> (There are a few mysql-related m4 files in autoconf-archive,
> but that's not the same package as mysql/mariadb, I suppose.)

It's still present in the libmariadb-dev 10.6 package in Debian
Unstable.

> >+    dnl The [MYSQL_CLIENT] macro calls [_MYSQL_CONFIG] to locate mysql_config.
> >+
> >+    _MYSQL_CONFIG
>
> One caveat of m4 macros is that they may be left unexpanded if not
> found, and it is up to the tarball producer to ensure the m4 macro is
> expanded.  Over the years, I built the opinion that this is not always
> a nice experience to have.
>
> I would do away with _MYSQL_CONFIG and just attempt to run
> `mysql_config` out the blue. sh failing to execute mysql_config, or a
> compiler failing to find mysql.h as part of AC_CHECK_HEADER is a nicer
> experience than _MYSQL_CONFIG being left accidentally unexpanded.

I'll use `m4_ifdef` to add a fall-back.

J.

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