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Re: [bug #33134] spurious error when stdout is already closed

From: David Boyce
Subject: Re: [bug #33134] spurious error when stdout is already closed
Date: Wed, 20 Apr 2011 22:36:33 -0400

On Wed, Apr 20, 2011 at 9:58 PM, Philip Guenther <address@hidden> wrote:
> Could you explain why you think that's spurious?  Make wanted to write
> "date" to stdout and the write failed.  Seems legit to me.

That's actually not what generates the error message. I'm not sure why
it doesn't happen the way you say, but it doesn't. Did you look at the
patch? Here it is:

Index: main.c
RCS file: /sources/make/make/main.c,v
retrieving revision 1.246
diff -u -r1.246 main.c
--- main.c      29 Aug 2010 23:05:27 -0000      1.246
+++ main.c      21 Apr 2011 00:53:24 -0000
@@ -952,7 +959,8 @@

-  atexit (close_stdout);
+  if (ftell(stdout) != -1)
+    atexit (close_stdout);

   /* Needed for OS/2 */

Basically in a (sensible and nicely documented) attempt to detect all
errors, make does an explicit close of stdout just before exiting in
order to make one last check for failure modes. However, it makes the
mistake of assuming stdout was open to start with. So in fact what the
child process did with stdout has nothing to do with this bug. It's as
simple as closing an already-closed file descriptor and printing the
resulting error, and my patch is as simple as "only close it if it's

> (I'm not sure why it doesn't say "make: write error: Bad file
> descriptor" like it does if you change the command invoked to ":", but
> that's a distinct issue.)

I noticed this and found it interesting as well. It gets even stranger
too: looking at close_stdout() there are two possible messages:

  if (prev_fail || fclose_fail)
      if (fclose_fail)
        error (NILF, _("write error: %s"), strerror (errno));
        error (NILF, _("write error"));
      exit (EXIT_FAILURE);

If you try the test case with -jN you get the first error but with -j
alone you get the second one.


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