[Bug stdio/29459] New: fwrite does not return EPIPE when underlying write fails with EPIPE.

[Bug stdio/29459] New: fwrite does not return EPIPE when underlying write fails with EPIPE.

[carlos at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29459

            Bug ID: 29459
           Summary: fwrite does not return EPIPE when underlying write
                    fails with EPIPE.
           Product: glibc
           Version: 2.36
            Status: NEW
          Severity: normal
          Priority: P2
         Component: stdio
          Assignee: unassigned at sourceware dot org
          Reporter: carlos at redhat dot com
  Target Milestone: ---

This was reported downstream for CentOS 9 Stream here:
https://bugzilla.redhat.com/show_bug.cgi?id=2112672

The issue is an upstream issue that needs review.

The test case is attached from the downstream issue.

An strace shows the issue clearly:

1659979752.806415 write(1, "hello\n", 6) = 6
1659979752.806467 write(2, "1. fwrite wrote 6 bytes and ferror is 0\n", 40) =
40
1659979752.806517 write(1, "hello\n", 6) = -1 EPIPE (Broken pipe)
1659979752.806548 --- SIGPIPE {si_signo=SIGPIPE, si_code=SI_USER,
si_pid=202616, si_uid=1000} ---
1659979752.806563 write(2, "2. fwrite wrote 6 bytes and ferror is 1\n", 40) =
40

The underlying write fails with EPIPE, but fwrite doesn't itself fail.

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[Bug stdio/29459] fwrite does not return EPIPE when underlying write fails with EPIPE.

[carlos at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29459

Carlos O'Donell <carlos at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://bugzilla.redhat.com
                   |                            |/show_bug.cgi?id=2112672

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[Bug stdio/29459] fwrite does not return EPIPE when underlying write fails with EPIPE.

[carlos at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29459

--- Comment #1 from Carlos O'Donell <carlos at redhat dot com> ---
Created attachment 14264
  --> https://sourceware.org/bugzilla/attachment.cgi?id=14264&action=edit
test-fwrite.c

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[Bug stdio/29459] fwrite does not return EPIPE when underlying write fails with EPIPE.

[carlos at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29459

--- Comment #2 from Carlos O'Donell <carlos at redhat dot com> ---
POSIX says it shall fail with EPIPE:
https://pubs.opengroup.org/onlinepubs/9699919799/functions/fputc.html#
"An attempt is made to write to a pipe or FIFO that is not open for reading by
any process. A SIGPIPE signal shall also be sent to the thread."

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[Bug stdio/29459] fwrite does not return EPIPE when underlying write fails with EPIPE.

[schwab@linux-m68k.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29459

--- Comment #3 from Andreas Schwab <schwab@linux-m68k.org> ---
How exactly is the test program called?

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[Bug stdio/29459] fwrite does not return EPIPE when underlying write fails with EPIPE.

[carlos at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29459

--- Comment #4 from Carlos O'Donell <carlos at redhat dot com> ---
(In reply to Andreas Schwab from comment #3)
> How exactly is the test program called?

./fwrite -l hello 5000 | head -n1

Such that head terminates and closes the pipe after reading one line.

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[Bug stdio/29459] fwrite does not return EPIPE when underlying write fails with EPIPE.

[sam at gentoo dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29459

Sam James <sam at gentoo dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sam at gentoo dot org

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