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Subject: printf
Date: Wed, 1 Aug 2007 13:12:21 -0400
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From: "Frederich, Eric P21322" <eric DOT frederich AT siemens DOT com>
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Hello guys,

I came across this page comparing different implementations of printf.
http://www.and.org/vstr/printf_comparison

The author says...
"Note that if you want a portable version of printf() in your code, you
are _much_ better off using something that natively parses the format
string. This ensures that you get the same parsing behavior on all
platforms"

If in cygwin, I have a c file like so...

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char* argv[]){
    printf("Which printf am I using?\n");
}


... and I compile it under cygwin with "gcc -mno-cygwin test.c"...
Would I be using one that "natively parses the format string"?
... now if I compile without the -mno-cygwin option, what happens?


I was looking around in some gcc source code for printf and found
vprintf.c which calls vfprintf.c with stdout, which calls _doprnt.
All of these were in a directory called "libiberty".  Furthermore, the
_doprnt winds up calling fprintf.

Does GCC have it's own implementation of printf and is it different than
glibc's implementation?

As you can tell, I don't understand much about this.  Why would both gcc
and glibc have a printf implementation?  Any help is appreciated.

I am also looking into this because I wanted to create my own
specialized version of printf which prints to two files with just one
function call.  I would be doing some different things on each file.  I
was looking for a good vfprintf to start with.

Thanks,
~Eric

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