[Bug libc/1190] fgetc()/fread() behaviour is not POSIX compliant

[Bug libc/1190] fgetc()/fread() behaviour is not POSIX compliant

[bugdal at aerifal dot cx]

http://sourceware.org/bugzilla/show_bug.cgi?id=1190

--- Comment #7 from Rich Felker <bugdal at aerifal dot cx> 2011-10-27 02:08:30 UTC ---
Created attachment 6036
  --> http://sourceware.org/bugzilla/attachment.cgi?id=6036
Tiny test-case showing the bug.

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[Bug libc/1190] fgetc()/fread() behaviour is not POSIX compliant

[bugdal at aerifal dot cx]

http://sourceware.org/bugzilla/show_bug.cgi?id=1190

Rich Felker <bugdal at aerifal dot cx> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
                 CC|                            |bugdal at aerifal dot cx
         Resolution|WORKSFORME                  |

--- Comment #6 from Rich Felker <bugdal at aerifal dot cx> 2011-10-27 02:07:43 UTC ---
This bug still exists; I'm reopening it and adding a new attachment that
demonstrates it trivially. Actually I wrote this test-case a while back as a
demonstration of one of the very few safe uses of gets(), which happened to
become unsafe due to the bug in glibc.

To see the bug, run the program (stdio_eof.c) and press ^D (or whatever your
EOF key on the terminal is). The program should exit, but under glibc, the
gets() call waits for a line of input and prints it back before exiting.

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[Bug libc/1190] fgetc()/fread() behaviour is not POSIX compliant

[gotom at debian dot or.jp]

http://sourceware.org/bugzilla/show_bug.cgi?id=1190

GOTO Masanori <gotom at debian dot or.jp> changed:

           What    |Removed                     |Added
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                 CC|                            |gotom at debian dot or.jp
         AssignedTo|gotom at debian dot or.jp   |drepper.fsp at gmail dot
                   |                            |com

--- Comment #8 from GOTO Masanori <gotom at debian dot or.jp> 2011-11-04 18:31:35 UTC ---
It looks like "end-of-file" condition is cleared when gets() called (which
should be preserved according to the standard), like:

#include <stdio.h>
int main(void) {
  char buf[100];
  gets(buf);  // We need to type ^D
  gets(buf);  // We need to type ^D but the stream already received ^D
(end-of-file condition)
}

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[Bug stdio/1190] fgetc()/fread() behaviour is not POSIX compliant

[jsm28 at gcc dot gnu.org]

http://sourceware.org/bugzilla/show_bug.cgi?id=1190

Joseph Myers <jsm28 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|libc                        |stdio

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[Bug stdio/1190] fgetc()/fread() behaviour is not POSIX compliant

[funtoos at yahoo dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=1190

--- Comment #9 from Sunil <funtoos at yahoo dot com> 2012-02-21 01:41:06 UTC ---
Can't believe its almost 7 yrs since I opened this bug. And it still
exists...:)

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[Bug stdio/1190] fgetc()/fread() behaviour is not POSIX compliant

[bugdal at aerifal dot cx]

http://sourceware.org/bugzilla/show_bug.cgi?id=1190

--- Comment #10 from Rich Felker <bugdal at aerifal dot cx> 2012-03-17 20:34:20 UTC ---
Ping. Now that there's a new willingness to fix longstanding glibc bugs, please
examine this report again.

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[Bug stdio/1190] fgetc()/fread() behaviour is not POSIX compliant

[jsm28 at gcc dot gnu.org]

http://sourceware.org/bugzilla/show_bug.cgi?id=1190

Joseph Myers <jsm28 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|drepper.fsp at gmail dot    |unassigned at sourceware
                   |com                         |dot org

--- Comment #11 from Joseph Myers <jsm28 at gcc dot gnu.org> 2012-03-18 14:20:03 UTC ---
This report appears to be correct and still present in current sources (tested
x86_64).

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[Bug stdio/1190] fgetc()/fread() behaviour is not POSIX compliant

[siddhesh at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=1190

Siddhesh Poyarekar <siddhesh at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |ASSIGNED
                 CC|                            |siddhesh at redhat dot com
         AssignedTo|unassigned at sourceware    |siddhesh at redhat dot com
                   |dot org                     |

--- Comment #12 from Siddhesh Poyarekar <siddhesh at redhat dot com> 2012-09-13 13:32:49 UTC ---
I'll take a crack at this.

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[Bug stdio/1190] fgetc()/fread() behaviour is not POSIX compliant

[siddhesh at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=1190

--- Comment #13 from Siddhesh Poyarekar <siddhesh at redhat dot com> 2012-09-13 13:52:06 UTC ---
The change is quite simple, but a comment in fileops.c says that this behaviour
is retained for sysv compatibility:

...
int
_IO_new_file_underflow (fp)
     _IO_FILE *fp;
{
  _IO_ssize_t count;
#if 0
  /* SysV does not make this test; take it out for compatibility */
  if (fp->_flags & _IO_EOF_SEEN)
    return (EOF);
#endif

...

I'm not sure if this is valid anymore, so I'll try to find out what the current
status is, unless someone here already knows the answer.

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[Bug stdio/1190] fgetc()/fread() behaviour is not POSIX compliant

[siddhesh at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=1190

--- Comment #14 from Siddhesh Poyarekar <siddhesh at redhat dot com> 2012-09-13 14:14:36 UTC ---
The discussion can be followed (and contributed to) here:

http://sourceware.org/ml/libc-alpha/2012-09/msg00343.html

I am currently of the opinion that this change may break a lot of existing
programs and hence this fix may not be a good idea.

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[Bug stdio/1190] fgetc()/fread() behaviour is not POSIX compliant

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=1190

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://sourceware.org/bugz
                   |                            |illa/show_bug.cgi?id=29601

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[Bug libc/1190] fgetc()/fread() behaviour is not POSIX compliant

[drepper at redhat dot com]

------- Additional Comments From drepper at redhat dot com  2007-02-18 04:39 -------
No test program provided in more than a year.  Closing.

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           What    |Removed                     |Added
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             Status|WAITING                     |RESOLVED
         Resolution|                            |WORKSFORME


http://sourceware.org/bugzilla/show_bug.cgi?id=1190

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[Bug libc/1190] fgetc()/fread() behaviour is not POSIX compliant

[aj at suse dot de]

------- Additional Comments From aj at suse dot de  2005-12-30 15:31 -------
Please send a self-contained test program that shows the bug.

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http://sourceware.org/bugzilla/show_bug.cgi?id=1190

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[Bug libc/1190] fgetc()/fread() behaviour is not POSIX compliant

[funtoos at yahoo dot com]

------- Additional Comments From funtoos at yahoo dot com  2005-09-30 20:50 -------
its a simple thing. fgetc() needs to return EOF if EOF is what the last call had
returned and is set on the stream, even though there is new data ready to be
read. EOF should be explicitly cleared (by the programmer) before the next call
to fgetc() is made by the programmer. This is a simple POSIX compliance
requirement as per the links I provided. What do we need a test case for? Are
you saying that the behaviour reported in the example is not the current
behaviour of glibc?

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http://sourceware.org/bugzilla/show_bug.cgi?id=1190

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[Bug libc/1190] fgetc()/fread() behaviour is not POSIX compliant

[drepper at redhat dot com]

------- Additional Comments From drepper at redhat dot com  2005-09-28 05:34 -------
I'm not going to spend a second on this until I see a small, self-contained
testcase.

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[Bug libc/1190] fgetc()/fread() behaviour is not POSIX compliant

[funtoos at yahoo dot com]

------- Additional Comments From funtoos at yahoo dot com  2005-08-10 16:15 -------
sorry for 200/256 mess up. It should read 'process B does an fread() for 2000
bytes'. Also, processA wrote 256 bytes to begin the protocol.

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