528129 - libffi rebuilds even when nothing has changed

Status: RESOLVED FIXED

(Core :: js-ctypes, defect)

Description

[Robert O'Callahan (:roc) (email my personal email if necessary)]

When I do a full build --- without clobbering --- where nothing related to js-ctypes has changed, the source files for libffi are recompiled and libffi is relinked. This is unnecessary and wasteful.

Comment 1

[[e-mail]]

I see this too. It happens only when we rerun libffi's configure. Presumably that's invalidating too much and causes a full rebuild, and we want to bring it more in line with how ours work. What I don't know is whether our configure scripts a) generate a new Makefile every time configure is run, but our dependencies are such that a new Makefile alone won't cause a rebuild, or b) we detect that the output of configure is the same as the cached output and we don't regenerate Makefiles.

Pretty sure it's b), but perhaps ted can confirm?

Comment 2

[(not currently active) Ted Mielczarek]

I don't think our configure tries to not remake makefiles every time. It is careful about a few other things, like mozilla-config.h:
http://mxr.mozilla.org/mozilla-central/source/configure.in#8197
and autoconf.mk:
http://mxr.mozilla.org/mozilla-central/source/configure.in#8354

Comment 3

[[e-mail]]

Turns out all we need here is for libffi to have its own config.cache.

This will be fixed by one of the patches in bug 538216.

Comment 4

[[e-mail]]

Fixed per bug 538216.