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From: peter@sugar.UUCP (Peter da Silva)
Newsgroups: comp.lang.c
Subject: Problem with either ANSI 'C' or Dr Dobbs Journal.
Message-ID: <449@sugar.UUCP>
Date: Thu, 30-Jul-87 22:01:37 EDT
Article-I.D.: sugar.449
Posted: Thu Jul 30 22:01:37 1987
Date-Received: Thu, 6-Aug-87 07:18:04 EDT
Organization: Sugar Land UNIX - Houston, TX
Lines: 30

According to an article on ANSI 'C' in Dr Dobb's Journal, a prototype
with a fixed number of arguments means the routine may be called without
unwinding the stack on return... the assumption being that the called
routine popped its arguments with a "RET N" type instruction.

It then adds that if no prototype is provided, the function may be
assumed to have a fixed number of arguments.

This is dangerous, in that it breaks existing code. Example:

/* no #includes */
exec_system(s)
char *s;
{
	execl("/bin/sh", "sh", "-c", s, 0);
	printf("Shell not found.\n");
	return 0;
}

Execl will be called as a routine that expects a fixed number of args.
The stack will not be unwound. The routine will return to (probably) the
address of the string "/bin/sh", leading to unusual results.

On the other hand, if they don't make that assumption, any call you make
without prototypes will lead to the stack being unwound twice.

I don't know if there's an answer... perhaps this could be made an optional
and defeatable extension?
-- 
-- Peter da Silva `-_-' ...!seismo!soma!uhnix1!sugar!peter (I said, NO PHOTOS!)