Re: rebuilt 1 .cxx, linked 184 libraries

On Thu, Apr 04, 2013 at 10:37:27PM +0200, Michael Stahl wrote:
> this is strictly speaking a bug, and the main problem here is that C++
> takes an awful long time to rebuild (otherwise i would have added a
> makefile dependency already like i've done for Zip, InstallModule, Help
> etc. targets that are quick to rebuild).  hmmm... perhaps it would be
> easy and "good enough" to just re-link when the makefile changes

Might work.

> > Note the chromium guys dump the exported symbols and only rebuild deps if that
> > changed. We could do the same, but I dont think the added complexity and
> > possible loss of robustness of doing this on all platforms is justified by the
> > gain.
>
> actually i really like that idea, we should look at doing that some day...
>
> ... one other thing i've always dreamed of is to store the commands that
> were executed somewhere so we can rebuild files when you edit the
> makefile, but only if that actually changes your command line and not if
> your change is only for $some-other-platform-or-configuration... iirc
> Linux build system does something like that...

Thats tricky if the build rule is a pure function. Some command like
idlc-stuff, zip(?), java build whatever is in a dir -- they would need to
rebuild even if the command is unchanged.

But yeah, in general something nice-to-have, esp. since it makes the the rule
available without having to parse the whole thing for the whole tree. In a
fantasy future, if you e.g. have a DSCM telling you what changed without
stating everything, you could wlak the dep-tree forward, instead of backwards a
la tup (without the mindboggling achitecture choices tup did like storing a
graph in SQLite ...) and thus only walk a subtree.

Best,

Bjoern