Re: Question on AC_CHECK_HEADERS/AC_DEFINE interaction

[Pádraig Brady]

On 24/07/15 17:40, Ben Pfaff wrote:
> On Fri, Jul 24, 2015 at 09:29:45AM -0700, Jim Meyering wrote:
>> On Thu, Jul 23, 2015 at 8:29 AM, Pádraig Brady <address@hidden> wrote:
>>> At line 40 we AC_DEFINE(HAVE_SELINUX_SELINUX_H,0)
>>>   
>>> http://git.savannah.gnu.org/gitweb/?p=gnulib.git;a=blob;f=m4/selinux-selinux-h.m4;h=fd09b299;hb=HEAD#l40
>>> However that may already defined to 1 which is the case
>>> when compiling in -m32 mode but with only the first of these installed:
>>>
>>>   $ rpm -qf /usr/include/selinux/selinux.h
>>>   libselinux-devel-2.3-9.fc22.x86_64
>>>   libselinux-devel-2.3-9.fc22.i686
>>>
>>> In that edge case, -Werror will fail due to the redefinition,
>>> thus causing -Werror to not be used in the build.
>>>
>>> Quite the edge case I know, but I'm not sure how best to avoid.
>>> Perhaps we should not use AC_CHECK_HEADERS here,
>>> instead going lower level with AC_PREPROC_IFELSE(.. AC_DEFINE ..) ?
>>
>> If you can find a clean way to avoid it, go ahead.
>> However, isn't it easy just to refrain from using -Werror when running
>> ./configure?
> 
> I agree.
> 
> If one wants to develop with -Werror, though, it can be a little
> inconvenient to add -Werror after running configure.  For my own
> projects, I add a --enable-Werror configure option that automatically
> adds -Werror only after doing all of the configuration tests:
> 
> AC_DEFUN([PSPP_ENABLE_WERROR],
>   [AC_ARG_ENABLE(
>      [Werror],
>      [AC_HELP_STRING([--enable-Werror], [Add -Werror to CFLAGS])],
>      [], [enable_Werror=no])
>    AC_CONFIG_COMMANDS_PRE(
>      [if test "X$enable_Werror" = Xyes; then
>         CFLAGS="$CFLAGS -Werror"
>       fi])])
> 

Yes that makes more sense.
Thanks to both of you.

Pádraig.