Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!dogie.macc.wisc.edu!indri!xanth!kremer
From: kremer@cs.odu.edu (Lloyd Kremer)
Newsgroups: comp.lang.c
Subject: Re: printf() problem
Summary: C does not specify order of evaluation of function arguments
Keywords: C printf
Message-ID: <8648@xanth.cs.odu.edu>
Date: 26 Apr 89 19:55:40 GMT
References: <11657@hodge.UUCP> <89Apr26.092233edt.18850@me.utoronto.ca>
Organization: Old Dominion University, Norfolk, Va.
Lines: 29


In article <89Apr26.092233edt.18850@me.utoronto.ca> zougas@me.utoronto.ca
("Athanasios(Tom) Zougas") writes:

>C puts its function parameters on the stack in "reverse" order, i.e.
>the last item is on top
>
>It would happen in any C.


It's not C that specifies this behavior.  C has never specified any order
of evaluation for function arguments.  C does not even presume the existence
of a last-in-first-out stack onto which arguments could be pushed.  Some
implementations pass args in registers or through a static area reserved for
the purpose.  Some mix register passing and stack passing.

Even in fully stack-based implementations where reverse ordering is the norm,
it cannot be assumed in all cases.  Vagaries of code generation or, more
likely, subsequent optimization, can change the order of evaluation in specific
cases.

The correct solution is unchanged since the early days of C: do not assume
anything regarding the order of evaluation of function arguments.

-- 
					Lloyd Kremer
					Brooks Financial Systems
					...!uunet!xanth!brooks!lloyd
					Have terminal...will hack!