[Bug c/37785] New: printf + sleep = problems with output buffer

[Bug c/37785] New: printf + sleep = problems with output buffer

[alexcastan at gmail dot com]

PLATFORM

PC i386 + GNU/Linux Ubuntu Hardy 8.04 + GCC 4.2.3
Compiling and Linking options: none.

Excuse my poor English. (By the way, what is "Host triplet", "Target triplet",
"Build triplet"?)

BUG:

"printf" really prints at terminal when finds '\n' character. So if I have a
simple "printf" iteration without '\n' like this ...

  int n;
  for (n=10; n>=0; n--) {
    printf("%d ", n);
    sleep(1);
  };

... it doesn't works like expected. It just waits 10 seconds without printing
anything. After that prints whole line.

Another related problem with printf without '\n' and printf buffer using fork,
but I don't know if it is problem with printf or fork:

  int n, pid;
  for (n=10; n>=0; n--) {
    printf("%d ", n);
    sleep(1);
  };
  pid = fork();
  if (pid == -1)
    printf("Error\n");
  else 
    if (pid == 0)
      printf("I'm the child\n");
    else 
      printf("I'm the parent\n");

it prints TWO times   10 9 8 7 6 5 4 3 2 1 0
It is not that executes two times, but if the fork send again the buffer to the
screen.


-- 
           Summary: printf + sleep = problems with output buffer
           Product: gcc
           Version: 4.2.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: alexcastan at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37785

[Bug c/37785] printf without '\n' + sleep = problems with output buffer

[paolo dot carlini at oracle dot com]

------- Comment #1 from paolo dot carlini at oracle dot com  2008-10-09 18:36 -------
In any case, sorry but this has nothing to do with the compiler.


-- 

paolo dot carlini at oracle dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37785

[Bug c/37785] printf without '\n' + sleep = problems with output buffer

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2008-10-09 18:46 -------
FILEs only fushes its internal buffer when it encounters a newline or when done
explicitly.  Do it explicitly, use fflush (stdout);.

Anyways this is not a compiler or a library issue.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37785

[Bug c/37785] printf without '\n' + sleep = problems with output buffer

[alexcastan at gmail dot com]

------- Comment #3 from alexcastan at gmail dot com  2008-10-09 20:24 -------
Then the second problem it is also the normal behavior. The fork()
makes child inherit the unprinted parent buffer, then two similar buffers get
print later.

  10 9 8 7 6 5 4 3 2 1 0   I'm the child
  10 9 8 7 6 5 4 3 2 1 0   I'm the parent


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37785