+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(-Werror)
+ AC_SUBST([WERROR_CFLAGS], [$WARNING_CFLAGS])
+ WARNING_CFLAGS=
+ 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)
+fi
+
+# Checks for libraries.
+AC_DEFINE([_GNU_SOURCE],1,[Define to 1 for GNU C library extensions.])
+
+# Checks for header files.