Re: A VC8's bug??

From:
"miaohua1982@gmail.com" <miaohua1982@gmail.com>
Newsgroups:
microsoft.public.vc.language
Date:
5 Jan 2007 06:01:48 -0800
Message-ID:
<1168005708.351798.25140@v33g2000cwv.googlegroups.com>
Thank you very much for your answer.
"Igor Tandetnik =D0=B4=B5=C0=A3=BA
"

<miaohua1982@gmail.com> wrote in message
news:1168001092.497006.152700@51g2000cwl.googlegroups.com

the code is as follows:

#include<iostream>
using namespace std;
class A
{
public:
   int a;
   int b;
};

int main(int argc,char **argv)
{
   int (A::*pInt) = &A::a;
   if ( &A::a )
   {
       cout<<"OK1n"<<endl;
   }
  if( pInt)
 {
      cout<<"OK2"<<endl;
 }
   return 0;
}


Yes, looks like a codegen bug to me. Looking at disassembly, a
pointer-to-member is stored simply as offset from the beginning of the
class. In particular, the first data member is usually at offset 0 (as
it is in this example), and pointer to it is represented as four zero
bytes.

Since all-zeros is a valid pointer-to-member, a NULL pointer-to-member
is stored as 0xFFFFFFFF. When checking a variable, as in "if (pInt)",
the compiler correctly generates code that compares the value with
0xFFFFFFFF. But in the statement "if (&A::a)" the compiler checks
against 0x0, and that's a bug.
--
With best wishes,
    Igor Tandetnik

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necessarily a good idea. It is hard to be sure where they are going to
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