Re: <architecture> and <instruction-set>

From: David Abrahams (dave_at_[hidden])
Date: 2005-10-21 07:39:35

Vladimir Prus <ghost_at_[hidden]> writes:

> On Thursday 20 October 2005 20:20, Rene Rivera wrote:
>> David Abrahams wrote:
>> > Reece Dunn <msclrhd_at_[hidden]> writes:
>> >>How about:
>> >>
>> >><architecture> specifies the general CPU type being used. That is, what
>> >>architectural design is being used on the chip. For example, x86
>> >> specifies the Intel X86 based CPUs such as Pentium 4.
>> >>
>> >><instruction-set> specifies what CPU/assembler instructions are available
>> >> for the given architecture. For example, using the instructions
>> >> available with the AMD Athalon CPU.
>> >
>> > So far, I see no advantage in distinguishing these. What's the point
>> > of <architecture>, anyway?
>>
>> Link compatibility. For example an x86/i486 compiled object would be
>> compatible with an x86/athlon. Perhaps someone is wants the Athlon
>> instructions for one specific file.
>
> FWIW, we don't have any "link compatibility" notion in V2. It used to be 
> there, and some remnants still remain, but it never worked good enough to be 
> useful. Speaking of architecture, it's theoretically possible to link 
> together x86 and powerpc code, isn't this exactly what Apple's recent file 
> format does? So, "link compatibility" is a moot thing.

I don't know about that. When we start installing Jamfiles with built
libraries, it might at the very least be helpful to issue warnings
when people try to use BB to link those libraries with executables
having incompatible build options.

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