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From: newsuser@LTH.Se (LTH network news server)
Newsgroups: comp.lang.c++
Subject: Bug in AT&T C++ 1.2
Summary: Nasty bug, trivial example
Message-ID: <1989Apr10.140143.19639@LTH.Se>
Date: 10 Apr 89 13:01:43 GMT
Reply-To: dag@Control.LTH.Se (Dag Bruck)
Organization: Dept. of Automatic Control, Lund Inst. of Technology, Sweden
Lines: 45


I have just found bug AT&T cfront 1.2.  It may be well-known to many
people, but maybe not to everybody. (Is this the last possibility to
report bugs on 1.2 ? (:-))

Source program follows:

	class C {
	public:
	  void f(float);
	  virtual void g(float);
	};

	main ()
	{
	  C x;

	  x.f(1);	// ok
	  x.g(1);	// error
	}

Calling the non-virtual C::f(), the integer 1 is converted to a floating
point 1.  Calling the virtual C::g(), no conversion takes place.

My compiler (with the fixes supplied with InterViews) produces this main
program (#line directives removed):

	int main (){ _main(); 
	{ 
	struct C _au1_x ;
	
	( ( ((& _au1_x )-> _C__vptr =  C__vtbl), (((& _au1_x )))) ) ;
	
	_C_f ( & _au1_x , (float )1 ) ;
	(*(((char (*)())(*(& _au1_x )-> _C__vptr ))))( & _au1_x , 1 ) ;
	}
	};


Dag Bruck
-- 
Department of Automatic Control		Internet:  dag@control.lth.se
Lund Institute of Technology
P. O. Box 118				Phone:	+46 46-108779
S-221 00 Lund, SWEDEN			Fax:    +46 46-138118