tweak comment

[gnulib.git] / lib / closeout.c

diff --git a/lib/closeout.c b/lib/closeout.c
index a4a986f..bdda59f 100644 (file)
--- a/lib/closeout.c
+++ b/lib/closeout.c
@@ -1,5 +1,5 @@
 /* closeout.c - close standard output
-   Copyright (C) 1998 Free Software Foundation, Inc.
+   Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -33,28 +33,85 @@
 # define EXIT_FAILURE 1
 #endif
 
+#include <stdio.h>
+
 #include <errno.h>
 #ifndef errno
 extern int errno;
 #endif
 
-#include <stdio.h>
 #include "closeout.h"
 #include "error.h"
+#include "quotearg.h"
+#include "__fpending.h"
+
+static int default_exit_status = EXIT_FAILURE;
+static const char *file_name;
+
+/* Set the value to be used for the exit status when close_stdout is called.
+   This is useful when it is not convenient to call close_stdout_status,
+   e.g., when close_stdout is called via atexit.  */
+void
+close_stdout_set_status (int status)
+{
+  default_exit_status = status;
+}
+
+/* Set the file name to be reported in the event an error is detected
+   by close_stdout_status.  */
+void
+close_stdout_set_file_name (const char *file)
+{
+  file_name = file;
+}
+
+/* Close standard output, exiting with status STATUS on failure.
+   If a program writes *anything* to stdout, that program should `fflush'
+   stdout and make sure that it succeeds before exiting.  Otherwise,
+   suppose that you go to the extreme of checking the return status
+   of every function that does an explicit write to stdout.  The last
+   printf can succeed in writing to the internal stream buffer, and yet
+   the fclose(stdout) could still fail (due e.g., to a disk full error)
+   when it tries to write out that buffered data.  Thus, you would be
+   left with an incomplete output file and the offending program would
+   exit successfully.
+
+   FIXME: note the fflush suggested above is implicit in the fclose
+   we actually do below.  Consider doing only the fflush and/or using
+   setvbuf to inhibit buffering.
+
+   Besides, it's wasteful to check the return value from every call
+   that writes to stdout -- just let the internal stream state record
+   the failure.  That's what the ferror test is checking below.
+
+   It's important to detect such failures and exit nonzero because many
+   tools (most notably `make' and other build-management systems) depend
+   on being able to detect failure in other tools via their exit status.  */
 
-/* Close standard output, exiting with status STATUS on failure.  */
 void
 close_stdout_status (int status)
 {
-  if (ferror (stdout))
-    error (status, 0, _("write error"));
+  int e = ferror (stdout) ? 0 : -1;
+
+  if (__fpending (stdout) == 0)
+    return;
+
   if (fclose (stdout) != 0)
-    error (status, errno, _("write error"));
+    e = errno;
+
+  if (0 <= e)
+    {
+      char const *write_error = _("write error");
+      if (file_name)
+       error (status, e, "%s: %s", quotearg_colon (file_name), write_error);
+      else
+       error (status, e, "%s", write_error);
+    }
 }
 
 /* Close standard output, exiting with status EXIT_FAILURE on failure.  */
 void
 close_stdout (void)
 {
-  close_stdout_status (EXIT_FAILURE);
+  close_stdout_status (default_exit_status);
 }