-# Prerequisites of lib/strerror.c.
-AC_DEFUN([gl_PREREQ_STRERROR], [
- AC_CHECK_DECLS([strerror])
- AC_CHECK_HEADERS_ONCE([sys/socket.h])
- if test $ac_cv_header_sys_socket_h != yes; then
- dnl We cannot use AC_CHECK_HEADERS_ONCE here, because that would make
- dnl the check for those headers unconditional; yet cygwin reports
- dnl that the headers are present but cannot be compiled (since on
- dnl cygwin, all socket information should come from sys/socket.h).
- AC_CHECK_HEADERS([winsock2.h])
+dnl Detect if strerror(0) passes (that is, does not set errno, and does not
+dnl return a string that matches strerror(-1)).
+AC_DEFUN([gl_FUNC_STRERROR_0],
+[
+ REPLACE_STRERROR_0=0
+ AC_CACHE_CHECK([whether strerror(0) succeeds],
+ [gl_cv_func_strerror_0_works],
+ [AC_RUN_IFELSE(
+ [AC_LANG_PROGRAM(
+ [[#include <string.h>
+ #include <errno.h>
+ ]],
+ [[int result = 0;
+ char *str;
+ errno = 0;
+ str = strerror (0);
+ if (!*str) result |= 1;
+ if (errno) result |= 2;
+ if (strstr (str, "nknown") || strstr (str, "ndefined"))
+ result |= 4;
+ return result;]])],
+ [gl_cv_func_strerror_0_works=yes],
+ [gl_cv_func_strerror_0_works=no],
+ [dnl Be pessimistic on cross-compiles for now.
+ gl_cv_func_strerror_0_works="guessing no"])
+ ])
+ if test "$gl_cv_func_strerror_0_works" != yes; then
+ REPLACE_STRERROR_0=1
+ AC_DEFINE([REPLACE_STRERROR_0], [1], [Define to 1 if strerror(0)
+ does not return a message implying success.])