Re: [PATCH] autoconf: Add link tests to each AC_CHECK_FUNC() test

From: Junio C Hamano <gitster@pobox.com>
Date: Jun 9, 2009, 05:30 UTC
Message-ID: <7vprdet1n7.fsf@alter.siamese.dyndns.org>
In-Reply-To: <20090608212454.GA834@gmx.de>

Ralf Wildenhues <Ralf.Wildenhues@gmx.de> writes:

> Hello, and please forgive me for replying to a very old thread,
> <http://thread.gmane.org/gmane.comp.version-control.git/99159>.
> (BTW, is that frowned upon on this list?)

Not at all.

Show 12 quoted lines

> * Junio C Hamano wrote on Sun, Nov 02, 2008 at 09:04:21AM CET:
>> "David M. Syzdek" <david.syzdek@acsalaska.net> writes:
>> > Update configure.ac to test libraries for getaddrinfo, strcasestr, memmem,
>> > strlcpy, strtoumax, setenv, unsetenv, and mkdtemp.  The default compilers
>> > on FreeBSD 4.9-SECURITY and FreeBSD 6.2-RELEASE-p4 do not generate warnings
>> > for missing prototypes unless `-Wall' is used. This behavior renders the
>> > results of AC_CHECK_FUNC() void on these platforms. The test AC_SEARCH_LIBS()
>> > verifies a function is valid by linking to symbol within the system libraries.
>
> This description does not make sense.  AC_CHECK_FUNC does not take into
> account prototypes in the test; instead, it tries to link a program that
> requires the function symbol.

Yeah, I just looked at output from AC_CHECK_FUNC(); it creates main() that calls the function being checked and tries to see if the program links.

And SEARCH_LIBS() won't catch missing prototypes either.

> However, there might have been another reason altogether why David was
> seeing false configure test results on his system, and it would be
> interesting to know about them (both to possibly fix Autoconf, and the
> comment introducing GIT_CHECK_FUNC in configure.ac).

Yeah, I am interested, too. The closest BSD variant I happen to have access to is FreeBSD 7.2, and reverting the commit there does not seem to have any ill effects, so I'd like to know what breakage the patch fixed (or covered up).