Article: Q249045
Product(s): Microsoft C Compiler
Version(s): winnt:6.0
Operating System(s):
Keyword(s): kbtemplate kbCompiler kbCPPonly kbLangCPP kbVC600 kbVC600bug
Last Modified: 03-MAY-2001
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The information in this article applies to:
- The C/C++ Compiler (CL.EXE), included with:
- Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0
- Microsoft Visual C++, 32-bit Professional Edition, version 6.0
- Microsoft Visual C++, 32-bit Learning Edition, version 6.0
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SYMPTOMS
========
The compiler generates an error such as the following when a pointer-to-member
is used as a class template parameter.
error C2964: invalid expression as template parameter
CAUSE
=====
This C++ language feature has not yet been implemented in Visual C++.
RESOLUTION
==========
To not use the pointer-to-member as a template argument, pass it as a parameter
to the class constructor.
STATUS
======
Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.
MORE INFORMATION
================
Use the following sample code to reproduce the behavior:
#ifdef BUG
struct MyClass {
char a,b;
MyClass() : a('a'), b('b') {};
};
template<char MyClass::*member_ptr>
class AnotherClass {
private:
MyClass m_var;
public:
char value() { return m_var.*member_ptr; }
};
int main()
{
AnotherClass<&MyClass::a> var1;
AnotherClass<&MyClass::b> var2; //<<<< Causes compiler error.
return 0;
}
#else
// WORKAROUND
struct MyClass {
char a,b;
MyClass() : a('a'), b('b') {};
};
template<typename MbrType, typename ClassType>
class AnotherClass {
private:
MyClass m_var;
MbrType ClassType::*member_ptr;
public:
AnotherClass(MbrType ClassType::*mem_ptr) : member_ptr(mem_ptr) {}
char value() { return m_var.*member_ptr; }
};
int main()
{
AnotherClass<char,MyClass> var1(&MyClass::a);
AnotherClass<char,MyClass> var2(&MyClass::b);
return 0;
}
#endif
Additional query words:
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Keywords : kbtemplate kbCompiler kbCPPonly kbLangCPP kbVC600 kbVC600bug
Technology : kbVCsearch kbAudDeveloper kbCVCComp
Version : winnt:6.0
Issue type : kbbug
Solution Type : kbpending
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