On Wednesday 2013-09-04 18:45 +0900, Mike Hommey wrote: > On Wed, Sep 04, 2013 at 10:28:21AM +0100, L. David Baron wrote: > > On Wednesday 2013-09-04 00:31 -0700, Gregory Szorc wrote: > > > Assuming it sticks, bug 896797 just landed in inbound and changes > > > how EXPORTS/headers are installed. This may impact your developer > > > workflow if you modify EXPORTS in a moz.build file to add/remove > > > headers. > > > > > > Previously, headers were installed incrementally as part of make > > > directory traversal. In the new world, we write out a "manifest" of > > > headers when the build config is read from moz.build files and then > > > we install them in bulk at the top of the build. > > > > Does this undo the protection that the build tiers were designed > > for, which is to prevent "backwards" dependencies between parts of > > the build? (In other words, things like preventing XPCOM from > > depending on headers in layout, so that XPCOM could be used > > standalone.) > > > > Do we still care about ensuring this? If so, should we have some > > other mechanism (like having standalone builds and showing them on > > tbpl)? > > The way the tier build works is that we effectively make export in all > directories of a same tier before make libs. In practice, this means > xpcom had access to every header in platform already, and any tier built > before platform, for that matter. So only app headers weren't available > to xpcom, and that's not a lot of them. > > So, really, nothing was already there to prevent backwards dependencies. > At least not in a very long time (I don't remember if we ever did > (make export; make libs) recursively directory by directory instead of > tier by tier.)
So I was assuming that xpcom was in a different tier from layout; apparently that's not the case. (I thought it was originally, but my memory could be wrong.) But is it correct that this change means we no longer have the backwards-dependency checking for things in different tiers? -David -- 𝄞 L. David Baron http://dbaron.org/ 𝄂 𝄢 Mozilla https://www.mozilla.org/ 𝄂 Before I built a wall I'd ask to know What I was walling in or walling out, And to whom I was like to give offense. - Robert Frost, Mending Wall (1914)
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