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Eugene Lazutkin
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 Posted: Tue Dec 13, 2005 11:26 pm Post subject: vc8 bug? |
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I encountered a problem while switching from MSVC 7.1 to MSVC 8. I
was able to isolate it and reproduce it. Here it goes (obviously the real
code is not about arithmetics):
============================
#include <iostream>
using namespace std;
template< int I = 0 >
struct Helper
{
enum { RESULT = I };
template< int J > struct Add : public Helper< RESULT + J > {};
};
int main()
{
typedef Helper<>
::Add<1>
::Add<2>
::Add<3>
Result;
cout << Result::RESULT << endl;
return 0;
}
============================
MSVC 7.1 compiles it just fine producing the correct result. MSVC 8 blows
out on the 2nd use of Add<> complaining that "Add<> is not defined". As far
as I can tell it should be legal C++ code --- at least this is how I
interpret the standard.
If it's my misunderstanding, please explain. If it's a bug, I should file it
to MS as such.
Any help is appreciated.
Thank you in advance,
Eugene
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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Gene Bushuyev
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| Posted: Thu Dec 15, 2005 10:48 am Post subject: Re: vc8 bug? |
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"Eugene Lazutkin" <eugene_lazutkin (AT) hotmail (DOT) com> wrote
| Quote: | I encountered a problem while switching from MSVC 7.1 to MSVC 8. I
was able to isolate it and reproduce it. Here it goes (obviously the real
code is not about arithmetics):
============================
#include <iostream
using namespace std;
template< int I = 0
struct Helper
{
enum { RESULT = I };
template< int J > struct Add : public Helper< RESULT + J > {};
};
int main()
{
typedef Helper
::Add<1
::Add<2
::Add<3
Result;
cout << Result::RESULT << endl;
return 0;
}
============================
MSVC 7.1 compiles it just fine producing the correct result. MSVC 8 blows
out on the 2nd use of Add<> complaining that "Add<> is not defined". As
far
as I can tell it should be legal C++ code --- at least this is how I
interpret the standard.
If it's my misunderstanding, please explain. If it's a bug, I should file
it
to MS as such.
|
It does look like a compiler bug. The standard requires implicit
instantiation of the Helper<> classes (14.7.1/1). It looks like VC8
instantiates only the first Helper<0> class and breaks after that.
-- Gene Bushuyev
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
[ comp.lang.c++.moderated. First time posters: Do this! ]
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