858762 - allow to generate backend.mk files for only apart of the tree

Status: RESOLVED WONTFIX

(Firefox Build System :: General, defect)

Description

[Trevor Saunders (:tbsaunde)]

the most obvious usecase for this is something like this.  Consider that you have a built tree but want to build dmd which is a replace malloc lib.  So you need to generate memory/replace/dmd/{Makefile,backend.mk} generating Makefile is easy (atleast if a Makefile.in exists haven't checked if not you can just run config.status --file=memory/replace/dmd/Makefile but running config.status --file=memory/replace/dmd/backend.mk fails, and there's no other obvious way to produce it.

Comment 1

[Gregory Szorc [:gps]]

I'm going to say WONTFIX for this.

backend.mk files are just our current way of converting moz.build data into make targets [to support our existing recursive make backend]. A moz.build traversal is all or nothing because that is how moz.build files work. If we allow partial tree reading, that opens up all kinds of one-offs that we'll need to support. This would bee too much effort IMO and would undermine part of the design of moz.build files.

The goal is for moz.build reading (triggered via ./config.status) to be fast. On an SSD and modern CPU, it should only take a few seconds. So, partial tree reading wouldn't gain you much.