Re: [boost] [config] 'requres' doesn't take differing -std intoaccount

Subject: Re: [boost] [config] 'requres' doesn't take differing -std intoaccount
From: Vladimir Prus (vladimir.prus_at_[hidden])
Date: 2015-06-22 08:08:02

On 6/22/2015 2:41 PM, Peter Dimov wrote:
> Vladimir Prus wrote:
>
>> The problem is that running configuration checks for all unique set of properties is quite wasteful.
>
> Maybe. It works though. :-)
>
>> Say, the 'link' property usually has no effect on architecture and address-model,
>
> How could you know?

By examining all toolsets that support the 'link' property?

> The only safe choice is to encode everything. But if we're to continue to guess, I'd say
> that, at minimum, cxxflags can certainly affect the architecture and address-model and everything else, and are
> currently not encoded.

Yes, so if you do:

        b2 toolset=gcc

and then

        b2 toolset=gcc cxxflags="-m32"

then you'd get wrong cached results of configuration check for address-model.

It is possible to solve, in general, but it requires either creating directory paths using a
hash of property set (which is ugly), or storing a hash of property set is a separate data
store. I believe SCons is the only one that solves this (using the second approach).
Maybe it's because it's reasonable to assume that if people adding options such as "-m32" to
cxxflags know what they are doing?

- Volodya