error: avoid undefined use of stdout

* lib/error.c (error, error_at_line): Check that fd 1 is open
before flushing stdout.  Avoids a crash on cygwin when libsigsegv
is handling faults and the close_stdout module wants to report the
detection of closed stdout as an error.

Signed-off-by: Eric Blake <ebb9@byu.net>

diff --git a/ChangeLog b/ChangeLog
index 81e6d839c5dffbd589dd5cfe0f91e55af00854a3..e5ba82ebb96cf3a9307b3e4cd2b58bd8769e7115 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2009-07-18  Eric Blake  <ebb9@byu.net>
+
+       error: avoid undefined use of stdout
+       * lib/error.c (error, error_at_line): Check that fd 1 is open
+       before flushing stdout.  Avoids a crash on cygwin when libsigsegv
+       is handling faults and the close_stdout module wants to report the
+       detection of closed stdout as an error.
+
 2009-07-17  Eric Blake  <ebb9@byu.net>
 
        pipe: be robust in face of closed fds

diff --git a/lib/error.c b/lib/error.c
index 3177bd5d2cbc3802e3590e40732ca6c376762a31..f2d45d993ba719c6a90a98bdb070cfedc0f3920e 100644 (file)
--- a/lib/error.c
+++ b/lib/error.c
@@ -1,5 +1,5 @@
 /* Error handler for noninteractive utilities
-   Copyright (C) 1990-1998, 2000-2007 Free Software Foundation, Inc.
+   Copyright (C) 1990-1998, 2000-2007, 2009 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
    This program is free software: you can redistribute it and/or modify
@@ -85,6 +85,8 @@ extern void __error_at_line (int status, int errnum, const char *file_name,
 
 #else /* not _LIBC */
 
+# include <fcntl.h>
+
 # if !HAVE_DECL_STRERROR_R && STRERROR_R_CHAR_P
 #  ifndef HAVE_DECL_STRERROR_R
 "this configure-time declaration test was not run"
@@ -236,6 +238,12 @@ error (int status, int errnum, const char *message, ...)
                   0);
 #endif
 
+#if !_LIBC
+  /* POSIX states that fflush (stdout) after fclose is unspecified; it
+     is safe in glibc, but not on all other platforms.  fflush (NULL)
+     is always defined, but too draconian.  */
+  if (0 <= fcntl (1, F_GETFL))
+#endif
   fflush (stdout);
 #ifdef _LIBC
   _IO_flockfile (stderr);
@@ -295,6 +303,12 @@ error_at_line (int status, int errnum, const char *file_name,
                   0);
 #endif
 
+#if !_LIBC
+  /* POSIX states that fflush (stdout) after fclose is unspecified; it
+     is safe in glibc, but not on all other platforms.  fflush (NULL)
+     is always defined, but too draconian.  */
+  if (0 <= fcntl (1, F_GETFL))
+#endif
   fflush (stdout);
 #ifdef _LIBC
   _IO_flockfile (stderr);