Re: [boost] [wave) experiences

From: Paul Mensonides (pmenso57_at_[hidden])
Date: 2005-12-04 01:46:43

> -----Original Message-----
> From: boost-bounces_at_[hidden] 
> [mailto:boost-bounces_at_[hidden]] On Behalf Of Vambola Kotkas

> None of the available wave  flags did seemingly help. Not 
> that i need huge integers, however boost sometimes does have 
> way bigger ones so it must be legal?

It's not.  Or, more precisely, all values in expressions in #if or #elif
directives are promoted to the largest built-in type--namely, long or unsigned
long in current C++.  Beyond that, if I recall correctly, underflow and overflow
produced by arithmetic results in undefined behavior.

> MS Visual C++ 7.1 
> processes constants like 18446744073709551615 without any noise.
> See ... 1.33.0 boost/cstdint.hpp  line(263):
> # if ULONG_MAX == 18446744073709551615 // 2**64 - 1
> 
> Silly example 2:
> #define SHOW2(x) #x
> #define SHOW(x) SHOW2(Number is:##x)
> #pragma message( SHOW(__LINE__))
> Result:
> test.cpp(3): error: pasting the following two tokens does not 
> give a valid preprocessing token: ":" and "__LINE__"
> Maybe its buggy and MS made its preprocessor too lousy there  
> ... just for reference Visual C++ 7.1 preprocess result:

It is undefined behavior to paste together two tokens where the result is not a
single token.  In this case, and in most cases like this, the concatenation is
pointless:

#define SHOW(x) SHOW2(Number is:x)

Just for the record, BTW, VC++ has a horrible preprocessor.

Regards,
Paul Mensonides