Re: [Boost-build] Options for a compiler version

Subject: Re: [Boost-build] Options for a compiler version
From: Vladimir Prus (ghost_at_[hidden])
Date: 2013-05-20 04:16:20

On 18.05.2013 16:14, Edward Diener wrote:
> On 5/18/2013 5:01 AM, Juraj Ivančić wrote:
>> On 18.5.2013. 0:55, Edward Diener wrote:
>>
>>> Thanks, I will look at it.
>>
>> Attaching a much shorter and improved version which works with minor
>> version numbers.
>>
>>> The condition, which you say is "complex", appears to me as an end-user
>>> of a build system to be extraordinarily simple. I just do not understand
>>> why Boost Build cannot support natively such a scenario. The scenario
>>> itself is so common as to be almost ridiculous. Yet it is difficult to
>>> do without knowledge of the bjam language and the workings of Boost
>>> Build. I do not think that should be the case.
>>
>> I called the condition complex because it cannot be expressed using
>> simple feature conditions. It is still quite easy. Boost Build can
>> definitely support such a scenario natively, but I don't think it is
>> that common as you claim.
>
> The scenario I am encountering, in general, is that some action should be taken depending on a compiler and its major version number, or
> depending on a compiler and its major version and minor version number, or on a compiler and its version number on up, or on a compiler and
> its version number on down, or on a compiler and a range of version numbers, all of the latter as expressed by any of the notions of major
> version number, major and minor version number, or full version number.

For example, here are two versions output by gcc on my system

        gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5)
        gcc version 4.7.3 (Sourcery CodeBench 2013.05-21)

Both of them have a bunch of additional patches relative to FSF versions, and gcc build process provides a lot of knobs, and
even if we talk about any major feature introduced in 4.7 it quite possible that this feature does not really work on
ARM GNU/Linux targets. So checking for compiler version is not a very good solution.

In some cases, yes, useful decisions can be based on compiler version, and we have access to it for gcc, and we don't expose
it to Jamfiles in a particularly useful way. Part of the problem is that doing this is possible in either ugly way, or backward
incompatible way.

- Volodya