Re: Specifying AM_CPPFLAGS from within configure.ac

[Stepan Kasal]

Hello Jirko,

some nit picking:

Regarding your macro MY_CXX_OPTION, if you want to be really portable,
things can get even more scary.  See
http://lists.gnu.org/archive/html/autoconf/2005-05/msg00109.html
This will point you to latest sources in the 1.5.x branch of libtool.
(The thread continues at
http://lists.gnu.org/archive/html/autoconf/2005-06/msg00001.html )


On Thu, Jun 02, 2005 at 10:40:03PM +0200, Jirka Hanika wrote:
> MY_CXX_OPTION(warnings, [warnings], [-Wall -w -enable-warnings-or-whatever])

MY_CXX_OPTION([warnings], [warnings], ...)

all arguments have to be quoted.  It's good rule to keep, at least when we
educate beginners on this list.  ;-)

I think the definition of your macro can be improved.
Here is the new version:

AC_DEFUN([MY_CXX_OPTION],
[AC_CACHE_CHECK([for $2], [epos_cv_cxx_opt_$1],
[cat > conftest.cc <<EOF
#include <stdio.h>
int main(int argc, char **argv)
{
argc=argc; argv=argv; return 0;
}
EOF
epos_cv_cxx_opt_$1=unknown
for opt in $3; do
    ${CXX} ${opt} -o conftest conftest.cc 2>conftest2 1>&5 || continue
    msg=`cat conftest2`
    if test -z "$msg"; then
        epos_cv_cxx_opt_$1=$opt
        break
    fi
done
rm -f conftest conftest2 conftest.cc])
if test "x${epos_cv_cxx_opt_$1}" = xunknown; then
        $1=
else
        $1=$epos_cv_cxx_opt_$1
fi])

Some of the changes are only my taste, but some are important:

AC_DEFUN([MY_CXX_OPTION],
  -- quote the symbol, in case the definition is read twice.

cmd 2>conftest2   always creates conftest2

You forgot to rm conftest.cc.

test "x$epos_cv_cxx_opt_$1" = xunknown
You have to prepend the "x", for portability, see the Autoconf manual.

Have a nice day,
        Stepan Kasal