Add a comment.

[gnulib.git] / lib / fwriteerror.c

diff --git a/lib/fwriteerror.c b/lib/fwriteerror.c
index 4d4ad81..21bd098 100644 (file)
--- a/lib/fwriteerror.c
+++ b/lib/fwriteerror.c
@@ -1,11 +1,11 @@
 /* Detect write error on a stream.
-   Copyright (C) 2003-2006 Free Software Foundation, Inc.
+   Copyright (C) 2003-2006, 2008 Free Software Foundation, Inc.
    Written by Bruno Haible <bruno@clisp.org>, 2003.
 
-   This program is free software; you can redistribute it and/or modify
+   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
-   the Free Software Foundation; either version 2, or (at your option)
-   any later version.
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
 
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ -13,8 +13,7 @@
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
-   along with this program; if not, write to the Free Software Foundation,
-   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include <config.h>
 
@@ -24,16 +23,34 @@
 #include <errno.h>
 #include <stdbool.h>
 
-int
-fwriteerror (FILE *fp)
+static int
+do_fwriteerror (FILE *fp, bool ignore_ebadf)
 {
   /* State to allow multiple calls to fwriteerror (stdout).  */
   static bool stdout_closed = false;
 
-  if (fp == stdout && stdout_closed)
-    return 0;
+  if (fp == stdout)
+    {
+      if (stdout_closed)
+       return 0;
+
+      /* If we are closing stdout, don't attempt to do it later again.  */
+      stdout_closed = true;
+    }
 
-  /* Need to
+  /* This function returns an error indication if there was a previous failure
+     or if fclose failed, with two exceptions:
+       - Ignore an fclose failure if there was no previous error, no data
+        remains to be flushed, and fclose failed with EBADF.  That can
+        happen when a program like cp is invoked like this `cp a b >&-'
+        (i.e., with standard output closed) and doesn't generate any
+        output (hence no previous error and nothing to be flushed).
+       - Ignore an fclose failure due to EPIPE.  That can happen when a
+        program blocks or ignores SIGPIPE, and the output pipe or socket
+        has no readers now.  The EPIPE tells us that we should stop writing
+        to this output.  That's what we are doing anyway here.
+
+     Need to
      1. test the error indicator of the stream,
      2. flush the buffers both in userland and in the kernel, through fclose,
         testing for error again.  */
@@ -56,25 +73,52 @@ fwriteerror (FILE *fp)
        goto close_preserving_errno; /* errno is set here */
       /* Give up on errno.  */
       errno = 0;
-     close_preserving_errno:
-      /* There's an error.  Nevertheless call fclose(fp), for consistency
-        with the other cases.  */
-      {
-       int saved_errno = errno;
-       fclose (fp);
-       errno = saved_errno;
-       return -1;
-      }
+      goto close_preserving_errno;
     }
 
-  /* If we are closing stdout, don't attempt to do it later again.  */
-  if (fp == stdout)
-    stdout_closed = true;
-
-  if (fclose (fp))
-    return -1; /* errno is set here */
+  if (ignore_ebadf)
+    {
+      /* We need an explicit fflush to tell whether some output was already
+        done on FP.  */
+      if (fflush (fp))
+       goto close_preserving_errno; /* errno is set here */
+      if (fclose (fp) && errno != EBADF)
+       goto got_errno; /* errno is set here */
+    }
+  else
+    {
+      if (fclose (fp))
+       goto got_errno; /* errno is set here */
+    }
 
   return 0;
+
+ close_preserving_errno:
+  /* There's an error.  Nevertheless call fclose(fp), for consistency
+     with the other cases.  */
+  {
+    int saved_errno = errno;
+    fclose (fp);
+    errno = saved_errno;
+  }
+ got_errno:
+  /* There's an error.  Ignore EPIPE.  */
+  if (errno == EPIPE)
+    return 0;
+  else
+    return -1;
+}
+
+int
+fwriteerror (FILE *fp)
+{
+  return do_fwriteerror (fp, false);
+}
+
+int
+fwriteerror_no_ebadf (FILE *fp)
+{
+  return do_fwriteerror (fp, true);
 }