+# GNU M4 is needed to build the testsuite.
+BISON_AC_PROG_GNU_M4
+if test "$ac_cv_prog_gnu_m4" != yes; then
+ missing_dir=`cd $ac_aux_dir && pwd`
+ M4="$missing_dir/missing m4"
+fi
+
+AC_ARG_ENABLE(gcc-warnings,
+[ --enable-gcc-warnings turn on lots of GCC warnings (not recommended)],
+[case "${enableval}" in
+ yes|no) ;;
+ *) AC_MSG_ERROR([bad value ${enableval} for gcc-warnings option]) ;;
+ esac],
+ [enableval=no])
+if test "${enableval}" = yes; then
+ BISON_WARNING(-Wall)
+ BISON_WARNING(-W)
+ BISON_WARNING(-Wbad-function-cast)
+ BISON_WARNING(-Wcast-align)
+ BISON_WARNING(-Wcast-qual)
+ BISON_WARNING(-Wformat)
+ BISON_WARNING(-Wmissing-declarations)
+ BISON_WARNING(-Wmissing-prototypes)
+ BISON_WARNING(-Wnested-externs)
+ BISON_WARNING(-Wshadow)
+ BISON_WARNING(-Wstrict-prototypes)
+ BISON_WARNING(-Wwrite-strings)
+ CFLAGS="$CFLAGS $WARNING_CFLAGS"
+fi