Re: [boost] numeric_cast

Subject: Re: [boost] numeric_cast
From: Edward Diener (eldiener_at_[hidden])
Date: 2011-06-27 16:42:43

On 6/27/2011 12:59 PM, Stephan T. Lavavej wrote:
> [Mateusz Loskot]
>> Is location of #pragma relevant? Meaning, having #pragma nested in
>> #ifndef include guard vs. placing it in outer scope, makes difference or
>> not?
>
> VC doesn't care where the #pragma once is, but as I recall, other compilers care where the #ifndef is - they prefer it to be on the outside of everything else, except comments.

I doubt if any compiler cares where the #ifndef ( or #if !defined ) is. 
It is just C++ after all and the preprocessor should handle it according 
to the C++ standard. It has just become conventional to write:

#ifndef SOME_MACRO
#define SOME_MACRO

// header code

#endif

to include the header code just once in a translation unit. Surely 
compilers do not process this any differently when the #ifndef is placed 
at the beginning of a header file than anywhere else.