I've been playing with the following, along with Makefile.am changes
to use $(NO_WERROR) in place of -Wno-error. The idea is to put this
some place so that all the configure.in can use a common definition
for warnings. I've changed it so that --enable-werror and
--enable-build-warnings should be usable with compilers other than
gcc.
AC_DEFUN([AM_BINUTILS_WARNINGS],[
WARN_CFLAGS="-W -Wall -Wstrict-prototypes -Wmissing-prototypes"
AC_ARG_ENABLE(werror,
[ --enable-werror treat compile warnings as errors],
[case "${enableval}" in
yes | y) ERROR_ON_WARNING="yes" ;;
no | n) ERROR_ON_WARNING="no" ;;
*) AC_MSG_ERROR(bad value ${enableval} for --enable-werror) ;;
esac])
# Enable -Werror by default when using gcc
if test "${GCC}" = yes -a -z "${ERROR_ON_WARNING}" ; then
ERROR_ON_WARNING=yes
fi
NO_WERROR=
if test "${ERROR_ON_WARNING}" = yes ; then
WARN_CFLAGS="$WARN_CFLAGS -Werror"
NO_WERROR="-Wno-error"
fi
AC_ARG_ENABLE(build-warnings,
[ --enable-build-warnings Enable build-time compiler warnings],
[case "${enableval}" in
yes) ;;
no) WARN_CFLAGS="-w";;
,*) t=`echo "${enableval}" | sed -e "s/,/ /g"`
WARN_CFLAGS="${WARN_CFLAGS} ${t}";;
*,) t=`echo "${enableval}" | sed -e "s/,/ /g"`
WARN_CFLAGS="${t} ${WARN_CFLAGS}";;
*) WARN_CFLAGS=`echo "${enableval}" | sed -e "s/,/ /g"`;;
esac])
if test x"$silent" != x"yes" && test x"$WARN_CFLAGS" != x""; then
echo "Setting warning flags = $WARN_CFLAGS" 6>&1
fi
AC_SUBST(WARN_CFLAGS)
AC_SUBST(NO_WERROR)
])