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From: karl@ima.isc.com (Karl Heuer)
Newsgroups: comp.lang.c
Subject: Re: cdecl and pascal keywords
Message-ID: <1991Jan04.183243.21124@dirtydog.ima.isc.com>
Date: 4 Jan 91 18:32:43 GMT
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In article <2847@cirrusl.UUCP> dhesi%cirrusl@oliveb.ATC.olivetti.com (Rahul Dhesi) writes:
>In theory, there is no need for a "pascal" keyword if you're using ANSI C...

Unless the compiler is going to do cross-file analysis (e.g. with a fixup at
link time), it would have to assume that all non-variadic functions are
pascal-like.  (It's irrelevant whether or not a prototype is in scope, since
	int main(void) { return f(1); }
and
	extern int f(int);
	int main(void) { return f(1); }
are equivalent programs, irregardful of whether f() is defined with or without
a prototype in its own source file.)

But if the compiler treats non-variadic functions and variadic functions
differently, it would break the common (but non-ANSI) usage
	/* no <stdio.h>! */
	int main() { printf("hello, world\n"); return 0; }
because it doesn't know that printf() is variadic.

Conclusion: an implementation must do one of the following:

[0] Be prepared to distinguish variadic from non-variadic functions at link
time.

[1] Treat all functions as caller-pop (unless otherwise indicated by a
nonstandard keyword like "__pascal").

[2] Treat all non-variadic functions as callee-pop, and break old programs
such as the above.  (A warning "no prototype for printf()" helps here.)

[3] Recognize "printf" and friends as reserved words even when <stdio.h> is
missing.

Karl W. Z. Heuer (karl@ima.isc.com or uunet!ima!karl), The Walking Lint