Hello,
 if you compile the following code with DMC 8.42n, the compiler will issue
"Error: size of ?$HaltNow@$00 is not known".

If you comment out the initial "#define FAIL" line it compiles alright. As there is no reference to Something's copy constructor in the main(void) function I think the compiler should disregard its definition in both cases and hence always succeed.

The code snippet compilation with GCC 3.45, Intel 10.1 and MS VC 8.1. is error free.

Is it a bug then?

#define FAIL

template<bool b>
struct HaltNow;

template<>
struct HaltNow<false>
{};

template<typename T>
struct Something
{

	Something(void){}

#if defined(FAIL)
	Something(const Something& var);
#else
	Something(const Something& var)
	{
		HaltNow<true> halt;
	}
#endif
};


#if defined(FAIL)
template<typename T>
Something<T>::Something(const Something& var)
{
	HaltNow<true> halt;
}
#endif


int main(void)
{
	Something<int> some_traits;
	return 0;
}

Thank you,
Radovan

Added as:

http://bugzilla.digitalmars.com/issues/show_bug.cgi?id=25