va_start used in function with fixed args

[stinos]

Why do you need va_start in that function?

I'm using void InternalLogFunction( char* Format, va_list& Args, const int, const bool ); so i need va_start to initialize the va_list.

[jacek]

I'm using void InternalLogFunction( char* Format, va_list& Args, const int, const bool ); so i need va_start to initialize the va_list.

Indeed, I missed that.

The problem is that the standard doesn't say anything about using va_list in a function with fixed number of parameters, so compilers might behave differently. The parameter you pass to va_start() is defined as the rightmost one and if you follow the standard strictly this makes va_start() useless in your case.

The easiest solution would be to move those last two parameters to the front, but I assume you can't do that, so instead you could change your InternalLogFunction() to something similar to qDebug() stream:

void Log( const char* Format, const T0 arg0, const int iLevel, const bool bLineEnd )
{
  InternalLogStream( iLevel, bLineEnd, Format ) << arg0;
}

void Log( const char* Format, const T0 arg0, const int iLevel, const bool bLineEnd )
{
  InternalLogStream( iLevel, bLineEnd, Format ) << arg0;
}

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or something like that.

[stinos]

The easiest solution would be to move those last two parameters to the front, but I assume you can't do that, so instead you could change your InternalLogFunction() to something similar to qDebug() stream:

didn't think about that. Wouldn't it require partly reinventing the printf mechanism?

Suppose a case with 3 parameters:
Log( "%d %s %d", 3, "test", 3, level, true );
that would use
InternalLogStream( iLevel, bLineEnd, Format ) << arg0 << arg1 << arg2;
Each call to << should move on to the next '%' found in the format string, convert the argument, append result to internal string. That's what printf does..


edit after thinking it through: it's really not a bad idea at all. It would require a call to 'Flush' or so after the InternalLogStream() calls because it has no way of knowing which argument is the last one, but I like the fact it uses templates: there's no way you can write a call with an argument that doesn't support conversion as the compiler would spot it immedeately so it's safer than normal printf. It might be somewhat slower though, still have to figure that out.

[jacek]

Wouldn't it require partly reinventing the printf mechanism?

Yes, but you can't use printf() because of those last two parameters.