Re: autoconf-2.68: no AC_LANG_SOURCE call detected in body

[Ralf Corsepius]

 On 09/23/2010 04:45 PM, Eric Blake wrote:
> On 09/23/2010 08:33 AM, Ralf Corsepius wrote:
> > > Not only were they entirely silent, but most likely generated a broken
> > > configure. If you don't use AC_LANG_SOURCE, then you don't get the
> > > benefit of all the prior AC_DEFINEs being implicitly included before
> > > the body of your test, which leads to documented cases of
> > > mis-diagnosing whether a feature is present for a given build.
> > Actually, I don't need the AC_DEFINES in this particular case - Adding
> > them however, should not do much harm, either.
>
> If you truly don't need all the earlier AC_DEFINES for this particular 
> case, you could use:
>
> AC_COMPILE_IFELSE([AC_LANG_DEFINES_PROVIDED
> #ifndef foo
> choke me
> #endif
> ])
>
> as an alternative way to silence the warning;
Thanks for the hint.

> this is also mentioned in NEWS; but it requires more effort if you 
> want to be back-compatible to earlier autoconf:
>
> m4_ifndef([AC_LANG_DEFINES_PROVIDED],
> [m4_define([AC_LANG_DEFINES_PROVIDED])])
I need to be backward compatible ;)

> > Well, "really usable warnings" look a bit different than this warning.
> > They might be self-explanatory to you, but to me this warning was 
> > "Greek".
>
> If you have any suggestions on how to improve this message:
>
> configure.ac:6: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
> detected in body
I wish I had one :)
> which told you the exact line number of the problem, as well as called 
> out the macro name that was in question, and where the documentation 
> for that macro name:
As I already tried to express, this was a trimmed down excerpt of  a 
real world configuration, with the real warning being a little more complex:

configure.ac:25: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:25: the top level
configure.ac:26: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:26: the top level
configure.ac:27: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:27: the top level
configure.ac:25: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:25: the top level
configure.ac:26: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:26: the top level
configure.ac:27: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:27: the top level
configure.ac:27: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
../aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:27: the top level
configure.ac:29: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
../aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:29: the top level
configure.ac:27: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
../aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:27: the top level
configure.ac:29: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
../aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:29: the top level
configure.ac:27: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
../aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:27: the top level
configure.ac:29: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
../aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:29: the top level
configure.ac:27: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
../aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:27: the top level
configure.ac:29: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
../aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:29: the top level
configure.ac:27: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
../aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:27: the top level
configure.ac:27: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
../aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:27: the top level
configure.ac:27: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
../aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:27: the top level
configure.ac:27: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
../aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:27: the top level
configure.ac:25: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
../aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:25: the top level
configure.ac:25: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
../aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:25: the top level
configure.ac:25: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
../aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:25: the top level
configure.ac:25: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
../aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:25: the top level
configure.ac:25: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:25: the top level
configure.ac:26: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:26: the top level
configure.ac:27: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:27: the top level
configure.ac:25: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:25: the top level
configure.ac:26: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:26: the top level
configure.ac:27: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call 
detected in body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2591: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2607: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2053: AC_CACHE_CHECK is expanded from...
aclocal/check-cpuopts.m4:4: RTEMS_CHECK_CPUOPTS is expanded from...
configure.ac:27: the top level

... with the bug actually being in a macro in aclocal/check-cpuopts.m4

Isolating the excerpt wasn't really difficult, but wasn't trivial, either :)

Ralf