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diff m4/strerror.m4 @ 15308:a3ba680ad389

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strerror_r: fix OpenBSD behavior on 0 OpenBSD treats strerror_r(0,,) as a success, but with a message "Undefined error: 0"; while this is distinct from strerror_r(-1,,) returning "Unknown error: -1", it does not imply success. Meanwhile, if buf is short enough for ERANGE, then we can't use strstr to look for "Unknown" or "Undefined" in the resulting message, like we had been doing for strerror(). Fix this by shifting the burden - now the strerror-override code guarantees that 0 will have an override when needed. * lib/strerror-override.c (strerror_override): Also override 0 when needed. * lib/strerror-override.h (strerror_override): Likewise. * lib/strerror.c (strerror): Simplify, now that 0 override is done earlier. * lib/strerror_r.c (strerror_r): Likewise. * m4/strerror.m4 (gl_FUNC_STRERROR): Split detection of 0 behavior... (gl_FUNC_STRERROR_0): ...into new macro. * m4/strerror_r.m4 (gl_FUNC_STRERROR_R): Replace strerror_r if 0 is overridden. (gl_FUNC_STRERROR_R_WORKS): Avoid extra tests if 0 is broken. * modules/strerror-override (Files): Add strerror.m4. (configure.ac): Also provide override for 0 when needed. * doc/posix-functions/strerror.texi (strerror): Document this. * doc/posix-functions/perror.texi (perror): Likewise. Signed-off-by: Eric Blake <eblake@redhat.com>
author Eric Blake <eblake@redhat.com>
date Tue, 21 Jun 2011 08:50:51 -0600 (2011-06-21)
parents 66b65ce5da39
children 8250f2777afc
line wrap: on
line diff
--- a/m4/strerror.m4
+++ b/m4/strerror.m4
@@ -1,4 +1,4 @@
-# strerror.m4 serial 15
+# strerror.m4 serial 16
 dnl Copyright (C) 2002, 2007-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -8,33 +8,24 @@
 [
   AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
   AC_REQUIRE([gl_HEADER_ERRNO_H])
+  AC_REQUIRE([gl_FUNC_STRERROR_0])
   m4_ifdef([gl_FUNC_STRERROR_R_WORKS], [
     AC_REQUIRE([gl_FUNC_STRERROR_R_WORKS])
   ])
-  if test -z "$ERRNO_H"; then
+  if test "$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>
-             #include <errno.h>
            ]],
-           [[int result = 0;
-             char *str;
-             if (!*strerror (-2)) result |= 1;
-             errno = 0;
-             str = strerror (0);
-             if (!*str) result |= 2;
-             if (errno) result |= 4;
-             if (strstr (str, "nknown") || strstr (str, "ndefined"))
-               result |= 8;
-             return result;]])],
+           [[if (!*strerror (-2)) return 1;]])],
         [gl_cv_func_working_strerror=yes],
         [gl_cv_func_working_strerror=no],
         [dnl Be pessimistic on cross-compiles for now.
-         gl_cv_func_working_strerror=no])
+         gl_cv_func_working_strerror="guessing no"])
     ])
-    if test $gl_cv_func_working_strerror = no; then
+    if test "$gl_cv_func_working_strerror" != yes; then
       dnl The system's strerror() fails to return a string for out-of-range
       dnl integers. Replace it.
       REPLACE_STRERROR=1
@@ -48,7 +39,40 @@
     ])
   else
     dnl The system's strerror() cannot know about the new errno values we add
-    dnl to <errno.h>. Replace it.
+    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],
+[
+  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.])
+  fi
+])