Re: [boost] Defining compilers suggestion

From: David Abrahams (dave_at_[hidden])
Date: 2005-07-10 22:36:29

Edward Diener <eddielee_at_[hidden]> writes:

> David Abrahams wrote:
>> Edward Diener <eddielee_at_[hidden]> writes:
>> 
>> 
>>>David Abrahams wrote:
>>>
>>>>Edward Diener <eddielee_at_[hidden]> writes:
>>>>
>>>>
>>>>
>>>>>It would be much easier, and less confusing, when looking at compiler 
>>>>>workarounds in Boost code if their were defines for various 
>>>>>compilers/versions in a configuratiion header file such as:
>>>>>
>>>>>#define BOOST_COMPILER_SOME_COMPILER_LOWER (PREPROCESSOR_TAG >= nnnn)
>>>>>#define BOOST_COMPILER_SOME_COMPILER_UPPER (PREPROCESSOR_TAG <= nnnn)
>>>>>#define BOOST_COMPILER_SOME_COMPILER (BOOST_COMPILER_SOME_COMPILER_LOWER 
>>>>>&& BOOST_COMPILER_SOME_COMPILER_UPPER)
>>>>
>>>>
>>>>Not sure why you'd want to do that.  Then you only get a binary value
>>>>for BOOST_COMPILER_SOME_COMPILER.
>>>
>>>You would get a boolean of true or false.
>> 
>> 
>> That wouldn't be very useful in Boost.  If you look through Boost code
>> you'll find a lot of places where a <, <=,>, or >= comparison is
>> needed against a compiler version.
>
> The way I have set it up, for example, is to use
>
> #define BOOST_COMPILER_VC6 (...)
> #define BOOST_COMPILER_VC6_OR_LOWER (...)
> #define BOOST_COMPILER_VC6_OR_HIGHER (...)

That would be nasty for a compiler such as GCC.  Go take a look at the
releases page.

> ( along with th same for VC7, VC71, and VC8 )
>
> You could write:
>
> #if BOOST_COMPILER_VC6
> // code
> #endif
>
> or
>
> #if BOOST_COMPILER_VC6_OR_HIGHER (...)
> // code
> #endif
>
> or even
>
> #if BOOST_COMPILER_VC6 || BOOST_COMPILER_VC7
> // code
> #endif
>
> You can imagine the ease of any combinations you like.
>
> Of course if one would rather see:
>
> #if (BOOST_MSVC >= 1310)
> // code
> #endif
>
> or
>
> #if BOOST_WORKAROUND(BOOST_MSVC,>= 1310)+
> // code
> #endif
>
> because that is better, then why should I suggest otherwise ?

I don't know.

It doesn't only have to do with what I'd rather see, but with the
functionality provided by BOOST_WORKAROUND.  Have you read the entire
comment there?

>> 
>> 
>>>>I'd rather have a composite version number.
>>>
>>>I would rather know whether some compiler is being referred to or not.
>> 
>> 
>> Then learn what the version numbers mean?
>
> Specifying a compiler version via a macro makes the code much clearer.
> This does not keep anyone from using BOOST_MSVC if they like or even
> combining it with the compiler identiification macros shown above.

I'd rather have one consistent way to do these tests than have a giant
suite of testing macros for every compiler and version.

>> Well, I think I spoke too soon.  What you appear to be asking for
>> would add little of value to Boost and would undermine the
>> capabilities we get from BOOST_WORKAROUND.
>
> I would never want to "undermine" Boost code in any way.

Maybe that wasn't the best choice of words.  I just meant that we'd
lose the functionality provided by BOOST_WORKAROUND if we started
using the macros you suggest instead.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com