From: Tom Lane <tgl@sss.pgh.pa.us>
To: evsi@amazon.com
cc: pgsql-bugs@lists.postgresql.org, Andres Freund <andres@anarazel.de>
Subject: Re: BUG #19368: f54af9f does not create the correct macro for
 autotools build
In-reply-to: <19368-016d79a7f3a1c599@postgresql.org>
References: <19368-016d79a7f3a1c599@postgresql.org>
Comments: In-reply-to PG Bug reporting form <noreply@postgresql.org>
	message dated "Wed, 31 Dec 2025 00:25:09 +0000"
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Date: Wed, 31 Dec 2025 10:59:32 -0500
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PG Bug reporting form <noreply@postgresql.org> writes:
> The commit f54af9f2679d added a macro HAVE_LIBURING_QUEUE_INIT_MEM that is
> checked to see if slowdown from memory mappings can be avoided when using
> io_uring.
> This HAVE_LIBURING_QUEUE_INIT_MEM is set by Meson build after checking
> liburing.
> However, the autotools build seems to set a different macro,
> HAVE_IO_URING_QUEUE_INIT_MEM, which is never used.

> This means when the server is built with autotools, the slowdown when using
> io_uring can never be avoided.

This is indeed busted, but I'd argue that the autoconf build has the
right macro name and meson and the C code are using the wrong one:

  if cc.has_function('io_uring_queue_init_mem',
      dependencies: liburing, args: test_c_args)
    cdata.set('HAVE_LIBURING_QUEUE_INIT_MEM', 1)
  endif

That's clearly not following the "HAVE_function" convention.

			regards, tom lane