Re: [boost] [chrono] Dependency on math?

Subject: Re: [boost] [chrono] Dependency on math?
From: alex (alexhighviz_at_[hidden])
Date: 2015-01-10 16:43:20

> > If you would just tell the package manager which header files require
> > building and which not....

> 
> There must be information on each file, at least if the library isn't
marked
> header only. Both pieces of information can become stale after just one
> maintenance change, so it is brittle. 
>

Yes you would need information for each file, but you could have defaults
for the library or directories.

Would you call a code change that introduces a requirement to build
'maintenance' ? It would be a breaking change for users that did not build
before.

A code change that removes a requirement to build but not marked as such
would not cause a problem; it just means that sometimes the library would be
built superfluously. 

> There's also the question of where to
> store that information. Is it per host? per user?

Isn't it obvious that it should be per host? The user shouldn't be expected
to know?

> >
> > That is why I thought it would be good to always get all files of a
> > library, even if not all files are needed.
> 
> I was trying to imply that, indirectly, but the tool will need to be smart
> enough to know when the user expressly wanted Y versus needing Y
> because of X.

Isn't the whole idea that the users express what they want and then get the
package containing what they need?

> > > Since users can alter the contents of the installation directories,
> > > the tool must actually track all files it installs in order to be able
to
> > > reinstall missing files to correct user mistakes, too.

> That would still be an issue.

Yes, but very solvable and I would think it already needs to do this anyway.

>From you responses I gather that resolving dependencies at file level would
cause too many complications for built libraries but not so for header-only
libraries. Why not at least take advantage of the header-only status of a
large number of libraries? I suppose this would create an incentive to split
existing libraries into a built and header-only library, but that is not so
bad is it?