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

Ralf Wildenhues [off-list ref] 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.

* Junio C Hamano wrote on Sun, Nov 02, 2008 at 09:04:21AM CET:

quoted

"David M. Syzdek" [off-list ref] writes:

quoted

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).