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Path: utzoo!utgpu!water!watmath!clyde!cbosgd!ihnp4!homxb!mtuxo!mtune!rutgers!bellcore!faline!ulysses!allegra!alice!bs
From: bs@alice.UUCP
Newsgroups: comp.lang.c++
Subject: Re: BUG
Message-ID: <7329@alice.UUCP>
Date: Wed, 30-Sep-87 20:57:24 EDT
Article-I.D.: alice.7329
Posted: Wed Sep 30 20:57:24 1987
Date-Received: Sat, 3-Oct-87 09:20:59 EDT
References: <1131@water.waterloo.edu>
Organization: AT&T Bell Laboratories, Murray Hill NJ
Lines: 51
Summary: FIX and workaround



# From cbosgd!water.UUCP!pabuhr Mon Sep 28 22:05:29 1987
# Organization: U. of Waterloo, Ontario
# 
# /*
# It took me 4 hours to locate this problem in a large program.
# If you look at the C++ code generated for the inline procedure
# `identity', you will notice that it has been optimized into the
# same single constant! I need a drink.

	I guess I owe you one. Sorry. Thank you for finding that one.
	Have a look at my test::id() function.
	It doesn't trigger that bug.
# */
# 
# class test {
#    public:
# 	inline int identity(test *);
 	int id(test *h) { return this==h; }
# };
# 
# inline int test::identity(test *h) {
# 	if (this != h) {
# 		return(0);
# 	} else {
# 		return(1);
# 	}
# };
# 
# main() {
# 	test a, b;
# 
# 	a.identity(&a);
# 	a.identity(&b);

	a.id(&a);
	a.id(&b);
# }

You can fix that bug by going into expr::eval() in expr2.c and
adding one statement:

	int i1 = (e1) ? e1->eval() : 0;				// after
	int i2 = (e2) ? e2->eval() : 0;				// this

	if (binary_val && i1==9999 && i2==9999) {		// add this
		Neval = "";					// add this
		return 1;					// add this
	}							// add this
};