Where to find the source code of _IO_putc_unlocked (c, _IO_stdout); ?

oscaringolilingo · 12-21-2010, 07:05 PM

Hi, I'm new here, and well, I thought I might as well just cut to the chase regarding my own programming questions about linux. I am sorry if this strikes someone as rude and I'll try my best to answer other peoples questios to be proactive with this website.

Anyway, I posted this same question a while ago at yahoo answers (http://answers.yahoo.com/question/in...1163451AAjo5Xl) and still am waiting for a response, but I thought that might not have been the best place to put is so, the matter is this:

I was browsing for the source code of printf() from glibc ( http://ftp.gnu.org/gnu/glibc/glibc-2.8.tar.gz ) and in the file printf.c I discovered printf uses putc to print characters on screen, well, I checked the source code of putc in putc.c and found out it uses some strange function _IO_putc_unlocked (c, _IO_stdout); but I can't seem to find the source code for this function. Could anyone please tell me where to find this so I can finally understand the ultimate inner workings of printf?

BTW, here are the source codes of printf.c

Quote:

/* Copyright (C) 1991, 1995, 1996, 1997, 2001, 2004, 2006
Free Software Foundation, Inc.
This file is part of the GNU C Library.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */

#include <libioP.h>
#include <stdarg.h>
#include <stdio.h>

#undef printf

/* Write formatted output to stdout from the format string FORMAT. */
/* VARARGS1 */
int
__printf (const char *format, ...)
{
va_list arg;
int done;

va_start (arg, format);
done = vfprintf (stdout, format, arg);
va_end (arg);

return done;
}

#undef _IO_printf
ldbl_strong_alias (__printf, printf);
/* This is for libg++. */
ldbl_strong_alias (__printf, _IO_printf);

and of putc.c

Quote:

/* Copyright (C) 1991, 1995, 1996, 1997, 1998, 2002, 2003
Free Software Foundation, Inc.
This file is part of the GNU C Library.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */

#include "libioP.h"
#include "stdio.h"

#undef _IO_putc

int
_IO_putc (c, fp)
int c;
_IO_FILE *fp;
{
int result;
CHECK_FILE (fp, EOF);
_IO_acquire_lock (fp);
result = _IO_putc_unlocked (c, fp);
_IO_release_lock (fp);
return result;
}
INTDEF(_IO_putc)

#undef putc

#ifdef weak_alias
weak_alias (_IO_putc, putc)

#ifndef _IO_MTSAFE_IO
#undef putc_unlocked
weak_alias (_IO_putc, putc_unlocked)
#endif
#endif

SORRY! I ment http://ftp.gnu.org/gnu/glibc/glibc-2.8.tar.gz not http://ftp.gnu.org/gnu/glibc/glibc-2.9.tar.gz

And apparently printf.c uses vprintf.c, which uses vfprintf.c, which uses putc.c

Sergei Steshenko · 12-21-2010, 08:05 PM

The source (it's a macro) is in

libio/libio.h

file - 'grep -r ....' is your friend.

oscaringolilingo · 12-21-2010, 09:24 PM

I found what I was looking for here http://hostilefork.com/2010/03/14/wh...eets-the-road/

Thanks to Ratchetr from yahoo answers for that one.

And thank you also, Sergei.