error: account for the possibility of freopen (stdout).

[gnulib.git] / lib / error.c

diff --git a/lib/error.c b/lib/error.c
index 3177bd5..80168a8 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
@@ -27,6 +27,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 #if !_LIBC && ENABLE_NLS
 # include "gettext.h"
@@ -85,6 +86,8 @@ 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"
@@ -101,6 +104,31 @@ extern char *program_name;
 # endif        /* HAVE_STRERROR_R || defined strerror_r */
 #endif /* not _LIBC */
 
+static inline void
+flush_stdout (void)
+{
+#if !_LIBC && defined F_GETFL
+  int stdout_fd;
+
+# if GNULIB_FREOPEN_SAFER
+  /* Use of gnulib's freopen-safer module normally ensures that
+       fileno (stdout) == 1
+     whenever stdout is open.  */
+  stdout_fd = STDOUT_FILENO;
+# else
+  /* POSIX states that fileno (stdout) after fclose is unspecified.  But in
+     practice it is not a problem, because stdout is statically allocated and
+     the fd of a FILE stream is stored as a field in its allocated memory.  */
+  stdout_fd = fileno (stdout);
+# endif
+  /* 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 <= stdout_fd && 0 <= fcntl (stdout_fd, F_GETFL))
+#endif
+    fflush (stdout);
+}
+
 static void
 print_errno_message (int errnum)
 {
@@ -236,7 +264,7 @@ error (int status, int errnum, const char *message, ...)
                   0);
 #endif
 
-  fflush (stdout);
+  flush_stdout ();
 #ifdef _LIBC
   _IO_flockfile (stderr);
 #endif
@@ -295,7 +323,7 @@ error_at_line (int status, int errnum, const char *file_name,
                   0);
 #endif
 
-  fflush (stdout);
+  flush_stdout ();
 #ifdef _LIBC
   _IO_flockfile (stderr);
 #endif