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

Subject: Re: [boost] [config] 'requres' doesn't take differing -std intoaccount
From: John Maddock (jz.maddock_at_[hidden])
Date: 2015-06-22 11:59:20

>> 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?
>
I think you're giving folks altogether too much credit ;)

While it may not be possible to fix absolutely everything, if you know 
enough to place object files in different directories, then you know 
enough to configure them differently too.  IMO Peter is correct - you 
should assume that everything makes a difference unless you know 
otherwise - not the other way around.

John.