[Bug libc/12351] New: non-conformance in fgetc behavior with eof flag

[Bug libc/12351] New: non-conformance in fgetc behavior with eof flag

[random832 at fastmail dot us]

http://sourceware.org/bugzilla/show_bug.cgi?id=12351

           Summary: non-conformance in fgetc behavior with eof flag
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper.fsp@gmail.com
        ReportedBy: random832@fastmail.us


The C standard says "If the end-of-file indicator for the stream is set, or if
the stream is at end-of-file, the end-of-file indicator for the stream is set
and the fgetc function returns EOF."

glibc seems to ignore the end-of-file indicator, this can be shown by typing a
ctrl-d on a blank line on a tty, or by repeatedly calling fgetc on a file which
it has reached the end of and which another process is appending to.

See also (not mine)
http://sourceware.org/glibc/wiki/Feedback#fgetc_function_.2BAC8_compliance_to_standard

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[Bug libc/12351] non-conformance in fgetc behavior with eof flag

[drepper.fsp at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=12351

Ulrich Drepper <drepper.fsp at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |WORKSFORME

--- Comment #1 from Ulrich Drepper <drepper.fsp at gmail dot com> 2011-05-29 23:22:32 UTC ---
I don't know what you see.  You have to provide a self-contained small example
of what you think is a problem.  Then you can reopen the bug.

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[Bug libc/12351] non-conformance in fgetc behavior with eof flag

[random832 at fastmail dot us]

http://sourceware.org/bugzilla/show_bug.cgi?id=12351

--- Comment #2 from random832 at fastmail dot us 2011-05-30 03:48:36 UTC ---
The problem is, an example _cannot_ be self-contained - it requires interactive
tty input or a second process appending to the file.

The example code at the link is sufficient (if modified to read stdin instead
of a file), if you type the EOF character [ctrl-D on most systems by default],
it will correctly report EOF once, but then it will carry on reading text typed
after that when it should (according to standard) continue reporting EOF
indefinitely until clearerr is called.

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[Bug libc/12351] non-conformance in fgetc behavior with eof flag

[drepper.fsp at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=12351

--- Comment #3 from Ulrich Drepper <drepper.fsp at gmail dot com> 2011-05-30 13:17:05 UTC ---
(In reply to comment #2)
> The problem is, an example _cannot_ be self-contained - it requires interactive
> tty input or a second process appending to the file.

And what keeps you from writing such a code?  Call fork, has the second process
feed a file descriptor etc.  I haven't seen any indication of a problem and the
descriptor is absolutely not sufficient to reproduce any.

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[Bug libc/12351] non-conformance in fgetc behavior with eof flag

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=12351

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
              Flags|                            |security-

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