source: trunk/essentials/sys-apps/grep/m4/regex.m4

#serial 5001

dnl Initially derived from code in GNU grep.
dnl Mostly written by Jim Meyering.

dnl Usage: jm_INCLUDED_REGEX([lib/regex.c])
dnl
AC_DEFUN(jm_INCLUDED_REGEX,
  [
    dnl Even packages that don't use regex.c can use this macro.
    dnl Of course, for them it doesn't do anything.

    # Assume we'll default to using the included regex.c.
    ac_use_included_regex=yes

    # However, if the system regex support is good enough that it passes the
    # the following run test, then default to *not* using the included regex.c.
    # If cross compiling, assume the test would fail and use the included
    # regex.c.  The first failing regular expression is from `Spencer ere
    # test #75' in grep-2.3.
    AC_CACHE_CHECK([for working re_compile_pattern],
                   jm_cv_func_working_re_compile_pattern,
      AC_TRY_RUN(
        changequote(<<, >>)dnl
        <<
#include <stdio.h>
#include <regex.h>
          int
          main ()
          {
            static struct re_pattern_buffer regex;
            const char *s;
            re_set_syntax (RE_SYNTAX_POSIX_EGREP);
            /* Add this third left square bracket, [, to balance the
               three right ones below.  Otherwise autoconf-2.14 chokes.  */
            s = re_compile_pattern ("a[[:]:]]b\n", 9, &regex);
            /* This should fail with _Invalid character class name_ error.  */
            if (!s)
              exit (1);

            /* This should succeed, but doesn't for e.g. glibc-2.1.3.  */
            s = re_compile_pattern ("{1", 2, &regex);

           exit (s ? 1 : 0);
          }
        >>,
        changequote([, ])dnl

               jm_cv_func_working_re_compile_pattern=yes,
               jm_cv_func_working_re_compile_pattern=no,
               dnl When crosscompiling, assume it's broken.
               jm_cv_func_working_re_compile_pattern=no))
    if test $jm_cv_func_working_re_compile_pattern = yes; then
      ac_use_included_regex=no
    fi

    test -n "$1" || AC_MSG_ERROR([missing argument])
    syscmd([test -f $1])
    ifelse(sysval, 0,
      [

        AC_ARG_WITH(included-regex,
        [  --without-included-regex don't compile regex; this is the default on
                          systems with version 2 of the GNU C library
                          (use with caution on other system)],
                    jm_with_regex=$withval,
                    jm_with_regex=$ac_use_included_regex)
        if test "$jm_with_regex" = yes; then
          AC_LIBOBJ(regex)
        fi
      ],
    )
  ]
)