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dnl If we're using gcc, figure out which gcc options to use.
AC_DEFUN(AC_GCC_FLAGS,
[
if test $ac_cv_prog_gcc = yes; then
dnl Determine if gcc -Wall causes warnings on isascii(), etc.
AC_CACHE_CHECK(whether ${CC-cc} -Wall also needs -Wno-char-subscripts,
ac_cv_char_warn,
[
OLDCFLAGS=$CFLAGS
CFLAGS="$CFLAGS -Wall -Werror"
AC_TRY_COMPILE([#include <ctype.h>],
[ int i; char c = '0';
i = isascii(c);
i = isdigit(c);
i = isprint(c);
], ac_cv_char_warn=no, ac_cv_char_warn=yes)
CFLAGS=$OLDCFLAGS
])
dnl Determine if gcc can accept -Wno-unused
AC_CACHE_CHECK(whether ${CC-cc} accepts -Wno-unused, ac_cv_gcc_nounused,
[
OLDCFLAGS=$CFLAGS
CFLAGS="$CFLAGS -Wno-unused"
AC_TRY_COMPILE(, , ac_cv_gcc_nounused=yes, ac_cv_gcc_nounused=no)
CFLAGS=$OLDCFLAGS
])
dnl Determine if gcc can accept -Wno-char-subscripts
AC_CACHE_CHECK(whether ${CC-cc} accepts -Wno-char-subscripts, ac_cv_gcc_ncs,
[
OLDCFLAGS=$CFLAGS
CFLAGS="$CFLAGS -Wno-char-subscripts"
AC_TRY_COMPILE(, , ac_cv_gcc_ncs=yes, ac_cv_gcc_ncs=no)
CFLAGS=$OLDCFLAGS
])
if test ${ac_cv_gcc_nounused:-ERROR} = yes; then
UNUSED="-Wno-unused"
else
UNUSED=""
fi
dnl If gcc -Wall gives no warnings with isascii(), use "-Wall";
dnl Otherwise, if gcc -Wall gives isascii warnings:
dnl If we can use -Wno-char-subscripts, use "-Wall -Wno-char-subscripts"
dnl If can't use -Wno-char-subscripts, use no flags at all.
dnl In all cases use -Wno-unused if we have it and are using -Wall
if test ${ac_cv_char_warn:-ERROR} = no; then
EXTRAFLAGS="-Wall $UNUSED"
else
if test ${ac_cv_gcc_ncs:-ERROR} = yes; then
EXTRAFLAGS="-Wall -Wno-char-subscripts $UNUSED"
else
EXTRAFLAGS=""
fi
fi
else
EXTRAFLAGS=""
fi
CFLAGS="$CFLAGS $EXTRAFLAGS"
])
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