# ===========================================================================

#    http://www.gnu.org/software/autoconf-archive/ax_build_date_epoch.html

# ===========================================================================

#

# SYNOPSIS

#

#   AX_BUILD_DATE_EPOCH(VARIABLE[, FORMAT[, ACTION-IF-FAIL]])

#

# DESCRIPTION

#

#   Sets VARIABLE to a string representing the current time.  It is

#   formatted according to FORMAT if specified, otherwise it is formatted as

#   the number of seconds (excluding leap seconds) since the UNIX epoch (01

#   Jan 1970 00:00:00 UTC).

#

#   If the SOURCE_DATE_EPOCH environment variable is set, it uses the value

#   of that variable instead of the current time.  See

#   https://reproducible-builds.org/specs/source-date-epoch).  If

#   SOURCE_DATE_EPOCH is set but cannot be properly interpreted as a UNIX

#   timestamp, then execute ACTION-IF-FAIL if specified, otherwise error.

#

#   VARIABLE is AC_SUBST-ed.

#

# LICENSE

#

#   Copyright (c) 2016 Eric Bavier <bavier@member.fsf.org>

#

#   This program is free software: you can redistribute it and/or modify it

#   under the terms of the GNU General Public License as published by the

#   Free Software Foundation, either version 3 of the License, or (at your

#   option) any later version.

#

#   This program is distributed in the hope that it will be useful, but

#   WITHOUT ANY WARRANTY; without even the implied warranty of

#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General

#   Public License for more details.

#

#   You should have received a copy of the GNU General Public License along

#   with this program. If not, see <http://www.gnu.org/licenses/>.

#

#   As a special exception, the respective Autoconf Macro's copyright owner

#   gives unlimited permission to copy, distribute and modify the configure

#   scripts that are the output of Autoconf when processing the Macro. You

#   need not follow the terms of the GNU General Public License when using

#   or distributing such scripts, even though portions of the text of the

#   Macro appear in them. The GNU General Public License (GPL) does govern

#   all other use of the material that constitutes the Autoconf Macro.

#

#   This special exception to the GPL applies to versions of the Autoconf

#   Macro released by the Autoconf Archive. When you make and distribute a

#   modified version of the Autoconf Macro, you may extend this special

#   exception to the GPL to apply to your modified version as well.

#serial 1

AC_DEFUN([AX_BUILD_DATE_EPOCH],

[dnl

AC_MSG_CHECKING([for build time])

ax_date_fmt="m4_default($2,%s)"

AS_IF([test x"$SOURCE_DATE_EPOCH" = x],

 [$1=`date -u "+$ax_date_fmt"`],

 [ax_build_date=`date -u -d "@$SOURCE_DATE_EPOCH" "+$ax_date_fmt" 2>/dev/null \

                 || date -u -r "$SOURCE_DATE_EPOCH" "+$ax_date_fmt" 2>/dev/null`

  AS_IF([test x"$ax_build_date" = x],

   [m4_ifval([$3],

      [$3],

      [AC_MSG_ERROR([malformed SOURCE_DATE_EPOCH])])],

   [$1=$ax_build_date])])

AC_MSG_RESULT([$$1])

])dnl AX_BUILD_DATE_EPOCH