# strerror.m4 serial 17

dnl Copyright (C) 2002, 2007-2017 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

])