Re: AC_CHECK_FUNCS and gcc with -Werror

[Eric Blake]

According to Ralf Corsepius on 3/3/2010 4:04 AM:
> On 03/03/2010 11:52 AM, Steffen Dettmer wrote:
>> Hi,
>>
>> in configure.in I have:
>>
>> AC_CHECK_FUNCS(printf)

C89 guarantees the existence of printf - this particular use of
AC_CHECK_FUNCS is most likely unnecessary for any modern machine, unless
your goal is to port to an embedded system that doesn't provide all of C89.

>> cc1: warnings being treated as errors
>> conftest.c:67: warning: conflicting types for built-in function 'printf'
>>
>> what to do best here?
> Not using -Werror

That's been the standard advice for years now.  Don't do something if it
hurts.  -Werror is a can of worms - there is NO way to silence all
possible warnings for all possible compilers.  It's great on a
per-compiler build (for example, coreutils provides --enable-gcc-warnings,
which conditionally adds -Werror to CFLAGS if the compiler spuports it),
but only for the program itself, and not for the duration of the configure
run.

Meanwhile, there is a patch on the table to teach autoconf 2.66 how to
recognize and work around -Werror coupled with gcc; I hope to finish
reviewing and apply it soon.
http://lists.gnu.org/archive/html/bug-autoconf/2010-02/msg00040.html

-- 
Eric Blake   address@hidden    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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