Hello Dave, (and Mohan)
Thanks for the nice info.
I've downloaded uClibc code and ran ctags -R and searched down printf.
It looks like the main print path is (assuming __STDIO_BUFFERS : I guess user
level buffer for stdin, stdout, stderr) and assuming STDIO_GETC/PUTC_MACRO
defined. without the macro, it seems to directly go to __fputc_unlocked..)
printf -> vfprintf (very complex doing all the format conversions..) -> PUTC ->
putc_unlocked -> __FPUTC_UNLOCKED ->(after some macro conversion)
__fputc_unlocked -> __stdio_WRITE (sometime write only to buffer) -> __WRITE ->
__gcs.write -> write
in libc/stdio/_stdio.h, the __gcs.wirte is assigned to _cs_write and
in libc/stdio/_cs_funcs.c, the _cs_write function is defined as below.
ssize_t attribute_hidden _cs_write(void *cookie, const char *buf, size_t
bufsize)
{
return write(*((int *) cookie), (char *) buf, bufsize);
}
what does cs stand for here? (Hm.. seems like custom streams..in the code) and
I couldn't follow past write above. Where is the function write defined?
Any hint will be deeply appreciated and if I'm wrong with something, please
correct me.
Thanks and regards,
Chan
________________________________
From : "Dave Hylands" <dhyla...@gmail.com>
Sent : 2014-03-12 13:39:11 ( +09:00 )
To : Kim Chan <c...@etri.re.kr>
Cc : kernelnewbies@kernelnewbies.org <kernelnewbies@kernelnewbies.org>
Subject : Re: where is the printf source for busybox?
Hi,
On Tue, Mar 11, 2014 at 6:44 PM, Kim Chan
<c...@etri.re.kr<mailto:c...@etri.re.kr>> wrote:
>
>
> Hi,
> I've had this question for some time past and I would like to know the answer
> now..
> I wanted to follow a printf in busybox but couldn't find the source of the
> printf function.
> Then I throught probably the printf is provided by the system library where
> printf is connected to proper linux system call. (Is it printk?)
busybox is typically built using uclibc, which is here:
http://www.uclibc.org/
The printf source code within uclibc is here:
http://git.uclibc.org/uClibc/tree/libc/stdio/printf.c
It eveentually winds up in _vfprintf here:
http://git.uclibc.org/uClibc/tree/libc/stdio/_vfprintf.c
--
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.com<http://www.davehylands.com/>
_______________________________________________
Kernelnewbies mailing list
Kernelnewbies@kernelnewbies.org
http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
