# strerror.m4 serial 17
dnl Copyright (C) 2002, 2007-2016 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.

AC_DEFUN([gl_FUNC_STRERROR],
[
  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
  AC_REQUIRE([gl_HEADER_ERRNO_H])
  AC_REQUIRE([gl_FUNC_STRERROR_0])
  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
  m4_ifdef([gl_FUNC_STRERROR_R_WORKS], [
    AC_REQUIRE([gl_FUNC_STRERROR_R_WORKS])
  ])
  if test "$ERRNO_H:$REPLACE_STRERROR_0" = :0; then
    AC_CACHE_CHECK([for working strerror function],
     [gl_cv_func_working_strerror],
     [AC_RUN_IFELSE(
        [AC_LANG_PROGRAM(
           [[#include <string.h>
           ]],
           [[if (!*strerror (-2)) return 1;]])],
        [gl_cv_func_working_strerror=yes],
        [gl_cv_func_working_strerror=no],
        [case "$host_os" in
                   # Guess yes on glibc systems.
           *-gnu*) gl_cv_func_working_strerror="guessing yes" ;;
                   # If we don't know, assume the worst.
           *)      gl_cv_func_working_strerror="guessing no" ;;
         esac
        ])
    ])
    case "$gl_cv_func_working_strerror" in
      *yes) ;;
      *)
        dnl The system's strerror() fails to return a string for out-of-range
        dnl integers. Replace it.
        REPLACE_STRERROR=1
        ;;
    esac
    m4_ifdef([gl_FUNC_STRERROR_R_WORKS], [
      dnl If the system's strerror_r or __xpg_strerror_r clobbers strerror's
      dnl buffer, we must replace strerror.
      case "$gl_cv_func_strerror_r_works" in
        *no) REPLACE_STRERROR=1 ;;
      esac
    ])
  else
    dnl The system's strerror() cannot know about the new errno values we add
    dnl to <errno.h>, or any fix for strerror(0). Replace it.
    REPLACE_STRERROR=1
  fi
])

dnl Detect if strerror(0) passes (that is, does not set errno, and does not
dnl return a string that matches strerror(-1)).
AC_DEFUN([gl_FUNC_STRERROR_0],
[
  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
  REPLACE_STRERROR_0=0
  AC_CACHE_CHECK([whether strerror(0) succeeds],
   [gl_cv_func_strerror_0_works],
   [AC_RUN_IFELSE(
      [AC_LANG_PROGRAM(
         [[#include <string.h>
           #include <errno.h>
         ]],
         [[int result = 0;
           char *str;
           errno = 0;
           str = strerror (0);
           if (!*str) result |= 1;
           if (errno) result |= 2;
           if (strstr (str, "nknown") || strstr (str, "ndefined"))
             result |= 4;
           return result;]])],
      [gl_cv_func_strerror_0_works=yes],
      [gl_cv_func_strerror_0_works=no],
      [case "$host_os" in
                 # Guess yes on glibc systems.
         *-gnu*) gl_cv_func_strerror_0_works="guessing yes" ;;
                 # If we don't know, assume the worst.
         *)      gl_cv_func_strerror_0_works="guessing no" ;;
       esac
      ])
  ])
  case "$gl_cv_func_strerror_0_works" in
    *yes) ;;
    *)
      REPLACE_STRERROR_0=1
      AC_DEFINE([REPLACE_STRERROR_0], [1], [Define to 1 if strerror(0)
        does not return a message implying success.])
      ;;
  esac
])
