# putenv.m4
# serial 28
dnl Copyright (C) 2002-2025 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 From Jim Meyering.
dnl
dnl Check whether putenv ("FOO") removes FOO from the environment.
dnl The putenv in libc on at least SunOS 4.1.4 does *not* do that.

AC_DEFUN([gl_FUNC_PUTENV],
[
  AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
  AC_CACHE_CHECK([for putenv compatible with GNU and SVID],
    [gl_cv_func_svid_putenv],
    [AC_RUN_IFELSE(
       [AC_LANG_PROGRAM(
          [AC_INCLUDES_DEFAULT
           GL_MDA_DEFINES],
          [[
            /* Put it in env.  */
            if (putenv ("CONFTEST_putenv=val"))
              return 1;

            /* Try to remove it.  */
            if (putenv ("CONFTEST_putenv"))
              return 2;

            /* Make sure it was deleted.  */
            if (getenv ("CONFTEST_putenv") != 0)
              return 3;

            return 0;
          ]])],
       [gl_cv_func_svid_putenv=yes],
       [gl_cv_func_svid_putenv=no],
       [dnl When crosscompiling, assume putenv is broken.
        case "$host_os" in
                              # Guess yes on glibc systems.
          *-gnu* | gnu*)      gl_cv_func_svid_putenv="guessing yes" ;;
                              # Guess yes on musl systems.
          *-musl* | midipix*) gl_cv_func_svid_putenv="guessing yes" ;;
                              # Guess no on native Windows.
          mingw* | windows*)  gl_cv_func_svid_putenv="guessing no" ;;
                              # If we don't know, obey --enable-cross-guesses.
          *)                  gl_cv_func_svid_putenv="$gl_cross_guess_normal" ;;
        esac
       ])
    ])
  case "$gl_cv_func_svid_putenv" in
    *yes) ;;
    *)
      REPLACE_PUTENV=1
      ;;
  esac
])

# Prerequisites of lib/putenv.c.
AC_DEFUN([gl_PREREQ_PUTENV],
[
  AC_CHECK_DECLS_ONCE([_putenv])
])