[Mesa-dev] [PATCH] m4: add Werror when checking for compiler flags

[Eric Engestrom]

On Wednesday, 2018-10-24 11:26:56 -0700, Dylan Baker wrote:
> Quoting Emil Velikov (2018-10-24 10:57:00)
> > Seemingly that at some point clang started accepting _any_ flags,
> > whereas previously it would error out.
> > 
> > These days, you can give it -Whamsandwich and it will succeed, while
> > at the same time throwing an annoying warning.
> > 
> > Add -Werror so that everything gets flagged and set accordingly.
> > 
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=108082
> > Cc: Eric Engestrom <eric.engestrom at intel.com>
> > Cc: Dylan Baker <dylan at pnwbakers.com>
> > Cc: Vinson Lee <vlee at freedesktop.org>
> > Repored-by: Vinson Lee <vlee at freedesktop.org>
> > Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
> > ---
> >  m4/ax_check_compile_flag.m4 | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/m4/ax_check_compile_flag.m4 b/m4/ax_check_compile_flag.m4
> > index 51df0c09a7a..0fdca907e8b 100644
> > --- a/m4/ax_check_compile_flag.m4
> > +++ b/m4/ax_check_compile_flag.m4
> > @@ -55,6 +55,11 @@
> >  #   modified version of the Autoconf Macro, you may extend this special
> >  #   exception to the GPL to apply to your modified version as well.
> >  
> > +# Emil:
> > +# Toggle Werror since at some point clang started treating unknown -W
> > +# flags as warnings, succeeding with the build, yet issuing an annoying
> > +# warning.
> > +
> >  #serial 3
> >  
> >  AC_DEFUN([AX_CHECK_COMPILE_FLAG],
> > @@ -62,7 +67,7 @@ AC_DEFUN([AX_CHECK_COMPILE_FLAG],
> >  AS_VAR_PUSHDEF([CACHEVAR],[ax_cv_check_[]_AC_LANG_ABBREV[]flags_$4_$1])dnl
> >  AC_CACHE_CHECK([whether _AC_LANG compiler accepts $1], CACHEVAR, [
> >    ax_check_save_flags=$[]_AC_LANG_PREFIX[]FLAGS
> > -  _AC_LANG_PREFIX[]FLAGS="$[]_AC_LANG_PREFIX[]FLAGS $4 $1"
> > +  _AC_LANG_PREFIX[]FLAGS="$[]_AC_LANG_PREFIX[]FLAGS $4 $1 -Werror"
> >    AC_COMPILE_IFELSE([m4_default([$5],[AC_LANG_PROGRAM()])],
> >      [AS_VAR_SET(CACHEVAR,[yes])],
> >      [AS_VAR_SET(CACHEVAR,[no])])
> > -- 
> > 2.19.1
> > 
> 
> This seems like the most straightforward way to solve the issue, since otherwise
> you need to track which compiler you have.

Agreed; thanks for tracking it down!

> 
> Reviewed-by: Dylan Baker <dylan at pnwbakers.com>

Reviewed-by: Eric Engestrom <eric.engestrom at intel.com>