Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!lll-winken!uunet!jtsv16!isdserv!iemisi!jdurko
From: jdurko@iemisi.UUCP (John Durko)
Newsgroups: comp.lang.c
Subject: Re: printf() problem
Summary: order args are pushed
Keywords: C printf
Message-ID: <481@iemisi.UUCP>
Date: 28 Apr 89 19:59:33 GMT
References: <11657@hodge.UUCP>
Organization: Boeing Canada, Toronto, Canada
Lines: 47

In article <11657@hodge.UUCP>, jdm@hodge.UUCP (jdm) writes:
>     Perhaps someone could explain this printf() phenomena to me.
>
>     printf("%x %x %x %x\n", getc(fp), getc(fp), getc(fp), getc(fp));
>
>     Although the order of the data in the file is:
>
>         92 AB 4E 33
> 
>     printf() displays it as:
> 
>         33 4E AB 92

The problem here ( I think :-} ) is that the compiler is pushing the function 
arguments on the stack from right to left. Therefore the last argument on the
list is the first to be evaluated and the thus makes the first call
to getc(). 


The following code illustrates this:

#include <stdio.h>

main(){

	int i = 1;

	printf(" %d  %d  %d  %d  \n",i++,i++,i++,i++);

}

Compiled and run this produces 4 3 2 1 .

Can anybody tell me if this behavoir is "guaranteed" in C.  I know that each
argument expression must be evaluated fully before the next but could find
no "guarantee" on the order that it is done.

-- 
______________________________________________________________________________
    ___  ___  ___ ___ _     ___  
   /  / /  / /    /  /|  / /      John Durko, Boeing Canada, Toronto.
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 /__/ /__/ /__ _/_ /   / /__/     official until the urinalysis results 
    de Havilland Division	  are in!!!

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