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Path: utzoo!utgpu!water!watnot!watmath!clyde!rutgers!princeton!allegra!alice!bs
From: bs@alice.UUCP
Newsgroups: comp.lang.c++
Subject: Re: Variable constants
Message-ID: <6726@alice.uUCp>
Date: Sat, 14-Mar-87 20:49:59 EST
Article-I.D.: alice.6726
Posted: Sat Mar 14 20:49:59 1987
Date-Received: Sun, 15-Mar-87 08:06:26 EST
References: <2032@cit-vax.Caltech.Edu>
Organization: AT&T Bell Laboratories, Murray Hill NJ
Lines: 31
Summary: a fix



Jon Leech spotted this one:

	const int n = 20;
	double m[n][n];
	extern void foo(...);

	f() {
		foo(m, &n);
		double x[n];	// by now cfront has forgotten that n==20
		extern void fo(double m[n][n], const int *pc...);
	}

and comments "Perhaps Bjarne would care to comment? ``Fixed in 1.2''"
Unfortunately not, but here is a horrible hack that will allow cfront to
remember the value of integer constants after you have taken their address.
In expr2.c in expr::eval:

	case NAME:
	{	Pname n = (Pname)this; 
		if (n->n_evaluated && n->n_scope!=ARG) return n->n_val;
					// the following test is the fix:
		if (n->n_initializer
		&& n->n_initializer
		&& n->n_initializer->base==IVAL
		&& n->n_initializer->i1==n->n_val) return n->n_val;
		if (binary_val && strcmp(string,"_result")==0) return 8888;
		Neval = "cannot evaluate constant";
		return 1;
	}