m4/parse-datetime.m4

# parse-datetime.m4
# serial 28
dnl Copyright (C) 2002-2006, 2008-2026 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
dnl This file is offered as-is, without any warranty.

dnl Define HAVE_COMPOUND_LITERALS if the C compiler supports compound literals
dnl as in ISO C99.
dnl Note that compound literals such as (struct s) { 3, 4 } can be used for
dnl initialization of stack-allocated variables, but are not constant
dnl expressions and therefore cannot be used as initializer for global or
dnl static variables (even though gcc supports this in pre-C99 mode).
AC_DEFUN([gl_C_COMPOUND_LITERALS],
[
  AC_CACHE_CHECK([for compound literals], [gl_cv_compound_literals],
    [AC_COMPILE_IFELSE(
       [AC_LANG_PROGRAM(
          [[struct s { int i, j; };]],
          [[struct s t = (struct s) { 3, 4 };
            if (t.i != 0) return 0;]])
       ],
       [gl_cv_compound_literals=yes],
       [gl_cv_compound_literals=no])
    ])
  if test $gl_cv_compound_literals = yes; then
    AC_DEFINE([HAVE_COMPOUND_LITERALS], [1],
      [Define if you have compound literals.])
  fi
])

AC_DEFUN([gl_PARSE_DATETIME],
[
  dnl parse-datetime.c is generated from parse-datetime.y. It requires bison,
  dnl because parse-datetime.y uses bison specific features. It requires at
  dnl least bison-2.4 for %define api.pure.
  dnl bison is only needed for the maintainer (who touches parse-datetime.y).
  dnl But in order to avoid separate Makefiles or --enable-maintainer-mode,
  dnl we put the rule in general Makefile. Now, some people carelessly touch
  dnl the files or have a broken "make" program, hence the parse-datetime.c
  dnl rule will sometimes fire. To avoid an error, defines PARSE_DATETIME_BISON
  dnl to ":" if it is not present or too old.
  gl_PROG_BISON([PARSE_DATETIME_BISON], [2.4])

  dnl Prerequisites of lib/parse-datetime.h.
  AC_REQUIRE([gl_TIMESPEC])
  AC_REQUIRE([AC_C_RESTRICT])

  dnl Prerequisites of lib/parse-datetime.y.
  AC_REQUIRE([gl_BISON])
  AC_REQUIRE([gl_C_COMPOUND_LITERALS])
  AC_REQUIRE([gl_CLOCK_TIME])
  AC_REQUIRE([gl_TM_GMTOFF])
])