I'm deriving a class from the templated std::streambuf.  In MSVC.NET
2002 and also in GCC 3 and te Comeau compiler, this code compiles.
However in MSVC.NET 2003 alone does it not compile.

I had to implement a small workaround only for MSVC.NET 2003.  The code
for the class is as follows:
class goutbuf : public std::streambuf {
public:
   goutbuf();
   ~goutbuf();

   /**
    * If set, the next output will be an mlprintf instead of a mprintf, with
    * the specified coordinates.
    */
   void setNextWriteLoc(int x, int y);

protected:
   int sync();
   void flush_output();

#if (_MSC_VER == 1310 )
   //While still technically correct and valid, it's not quite as robust
as the
   //next line because this makes the assumption on what traits_type is
defined
   //as.
   int_type overflow(int_type meta = std::char_traits<char>::eof());
#else
   //For some reason, in MSVC.NET 2003 alone (not 2002), this line generates
   //the following error:
   //error C2653: 'char_traits<char>' : is not a class or namespace name
   int_type overflow(int_type meta = traits_type::eof());
#endif

   std::streamsize xsputn(const char_type *ptr, std::streamsize count);

private:
   char* buf;

   int x; //the next coords to write to, if not -1.
   int y;

Jason Winnebeck

-cd

The first answer is, if you look at the previous code with the workaround,
switching to std::char_traits<char> does work.

The second answer is that I am not using char_traits at all in the "correct"
code (the second part of the #if).  I'm using std::streambuf::traits_type.
And <streambuf> is included, espically seeing as goutbuf is declared from
streambuf.

If we look in the standard, std::streambuf::traits_type is a member (a
typedef) of the std::streambuf class, and its definition is
std::char_traits<char> for std::streambuf (which is std::basic_streambuf<char,
std::char_traits<char> >) as defined by 27.5 of the standard.  27.5.2 defines
the traits_type typedef for std::streambuf.

The code using traits_type compiles on MSVC.NET 2002, GCC 3, and Comeau.  I
can't see a reason why it should not work by the standard (and thus for 2003).

Perhaps, though, I will try including it.  But as I said, replacing the
typedef'd element of streambuf with its definition fixes the problem, which
is, I believe, to be a very clear sign that something is wrong.

If
typedef A B;
And if:
B x;
gives an error that "A" is not defined, but
A x;
does work, I would say this is not right.

Jason Winnebeck

-cd

#include <streambuf>

class goutbuf : public std::streambuf {
protected:
   int_type overflow(int_type meta = traits_type::eof());

C++ FAQ: http://www.parashift.com/c++-faq-lite/
C FAQ: http://www.eskimo.com/~scs/C-faq/top.html

Thanks for finding a tiny repro!

Jason -

This appears to be fixed in the Whidbey alpha.  If this is causing you
significant problems in yoiur production work, you should contact Product
Support Services.

-cd

Jason

#include <limits>
#undef max

template < typename T >
class A
{
protected:
    typedef std::numeric_limits< T >        MinMaxTy;
private:
    T t_;
public:
    A(const T t= MinMaxTy::max()) : t_(t) {}

"Jason Winnebeck" <gill...@mail.rit.nspam.edu> schrieb im Newsbeitrag
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