My book tells me that the compiler will automagically decide whether to
instantiate a basic_iostream with char or wchar_t and I want to do the same
with my class derived from the basic_iostream. I looked at the
implementation of iostream that came with my environment and I found:

#if defined(_DLL_CPPLIB) && !defined(_M_CEE_PURE)
template class _CRTIMP2_PURE basic_iostream<char, char_traits<char> >;
template class _CRTIMP2_PURE basic_iostream<wchar_t, char_traits<wchar_t> >;

my instinct would tell me to put the same defines for my derived class, but
I don't think that would be very portable, as I believe _DLL_CPPLIB,
_M_CEE_PURE, and _CRTIMP2_PURE to be MS specific or worse even compiler
specific. Is there some portable way to accomplish the same thing?

Even if I use #ifdef #endif blocks I wouldn't know what to put in them for
these defines for other OSes/Compilers.
Any advice?

Christopher wrote:
> My book tells me that the compiler will automagically decide whether
> to instantiate a basic_iostream with char or wchar_t and I want to do
> the same with my class derived from the basic_iostream. I looked at
> the implementation of iostream that came with my environment and I
> found:
> #if defined(_DLL_CPPLIB) && !defined(_M_CEE_PURE)
> template class _CRTIMP2_PURE basic_iostream<char, char_traits<char> >;
> template class _CRTIMP2_PURE basic_iostream<wchar_t,
> char_traits<wchar_t> >;
> my instinct would tell me to put the same defines for my derived
> class, but I don't think that would be very portable, as I believe
> _DLL_CPPLIB, _M_CEE_PURE, and _CRTIMP2_PURE to be MS specific or
> worse even compiler specific. Is there some portable way to
> accomplish the same thing?
> Even if I use #ifdef #endif blocks I wouldn't know what to put in
> them for these defines for other OSes/Compilers.
> Any advice?

I dont think it's the defines that are doing the deciding, but the fact that
there are two templates declared, one for char, one for wchar_t. If you
look at the #else there is probably 2 definitions after it just without
_CRTIMP2_PURE most likely. As it is, you still need to specify which
template to use. Take a look at your declaration of ifstream, for example,
and see how it decides which to instantize.

--
Jim Langston
tazmaster@rocketmail.com