Re: [Boost-build] feature, properties, variants, and all the rest

Subject: Re: [Boost-build] feature, properties, variants, and all the rest
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2017-09-29 21:14:11

AMDG

On 09/29/2017 01:07 PM, Stefan Seefeld via Boost-build wrote:
> On 29.09.2017 14:58, Steven Watanabe via Boost-build wrote:
>> On 09/29/2017 12:33 PM, Stefan Seefeld via Boost-build wrote:
>>> On 29.09.2017 14:20, Steven Watanabe via Boost-build wrote:
>>>> - It can scan headers that are generated during the build.
>>> and so can a compiler-based approach.
>>>
>> I don't know any perfect way to handle this.
>>
>> It's impossible to complete the scan before
>> building all the headers that are required.
> 
> A generated header is like any other artefacts (targets): before it
> exists, dependencies need to be explicitly provided to bjam. Once it
> does exist, it can be scanned.
> 

This is only practical when the number of
generated headers is very small.

> <snip>
> 
>> It's also impossible to determine which headers
>> are required before scanning.
> Well, for generated headers I would assume this information to be
> explicitly provided to the build tool. Are there situation where that's
> not practical ?
> 

b2 headers.  (The entire header tree is created by
copying from multiple sources.)

Also, `gcc -M` is very C specific.  For languages
that don't use the C preprocessor (or equivalent),
either you can calculate the dependencies accurately
a file at a time, or you can't calculate them perfectly
no matter how hard you try.

In Christ,
Steven Watanabe