857557 - Avoid autoconf.mk being modified for new other-platform-specific variables

Status: RESOLVED FIXED

(Firefox Build System :: General, defect)

Description

[Mike Hommey [:glandium]]

A common pattern that triggers autoconf.mk to be updated, thus making the build essentially a clobber is when we add a platform-specific variable. The variable usually has an empty value on other platforms, but the mere fact of adding its empty value in autoconf.mk makes the build a clobber. But besides $(origin), there's not much difference between a variable defined to nothing and a variable not defined at all in make.

Comment 1

[Mike Hommey [:glandium]]

Attachment: Avoid autoconf.mk being modified for new other-platform-specific variables

Comment 2

[Gregory Szorc [:gps]]

Comment on attachment 732793 [details] [diff] [review]
Avoid autoconf.mk being modified for new other-platform-specific variables

Review of attachment 732793 [details] [diff] [review]:
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Please add a code comment somewhere saying that filtering empty variables results in less invalidation of build dependencies.

Comment 3

[Mike Hommey [:glandium]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/43ec10ce6056

Comment 4

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/43ec10ce6056