safe alternative to va_arg [Visual C]

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From: Ulrich Eckhardt on 18 Apr 2008 07:20

Fabian wrote:
> is there any possibility to define default parameters? Default parameters
> for templates are the default types, right? But if I could do sth. like
>
> template void PrintError(const char*, const char* = 0, const char* = 0,
> const char* = 0, const char* = 0);

If you already know that you will only be logging strings, you don't need
any template, just an overloaded function with default argument like above.

Otherwise, my compiler claims that I can't use default template parameters
(_not_ functions parameters!) with template functions.

> for the specialization in the cpp file, I wouldn't have to write
> specializations for a different number of parameters. But the compiler
> (btw: I'm quite up to date: Visual Studio 2008) doesn't like it:
>
> 'PrintError' : an explicit specialization of a function template cannot
> have any default arguments

Well, of course you are not repeating the default arguments, right? You
never do that when you define a function that was declared with default
arguments.

Uli

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From: Fabian on 18 Apr 2008 08:37

Hello Uli,

> If you already know that you will only be logging strings, you don't need
> any template, just an overloaded function with default argument like above.

I am not sure that I'm always logging strings. I wrote overloads for the
template functions now - with a different number of arguments each:

// header file:
template <typename T1> COMMON_API inline void PrintError(const T1& arg1);
template <typename T1, typename T2> COMMON_API inline void PrintError(const
T1& arg1, const T2& arg2);
template <typename T1, typename T2, typename T3> COMMON_API inline void
PrintError(const T1& arg1, const T2& arg2, const T3& arg3);
// and so on...

// cpp file:
template <typename T1> void PrintError(const T1& arg1)
{
cerr << arg1 << endl;
}
template <typename T1, typename T2> void PrintError(const T1& arg1, const
T2& arg2)
{
cerr << arg1 << ": " << arg2 << endl;
}
template <typename T1, typename T2, typename T3> void PrintError(const T1&
arg1, const T2& arg2, const T3& arg3)
{
cerr << arg1 << ": " << arg2 << ", " << arg3 << endl;
}
// and so forth...

But when I now compile a specialization with more than one parameter I get a
compiler error:

template inline void COMMON_API PrintError<const char*>(const char*); // works
template inline void COMMON_API PrintError<const char*, const char*>(const
char*, const char*); // produces C2977

error C2977: 'PrintError' : too many template arguments

So what is this now???

Thanks for your patience with me,

Fabian

From: Fabian on 18 Apr 2008 08:38

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