Re: [PATCH 3/3] Makefile: split prefix flags from GIT-CFLAGS

Jeff King [off-list ref] writes:

On Tue, Jun 19, 2012 at 01:51:14PM -0700, Junio C Hamano wrote:

quoted

Jeff King [off-list ref] writes:

quoted

Most of the build targets do not care about the setting of $prefix
(or its derivative variables), but will be rebuilt if the prefix
changes. For most setups this doesn't matter (they set prefix once
and never change it), but for a setup which puts each branch or
version in its own prefix, this unnecessarily causes a full
rebuild whenever the branc is changed.

[...]

I have to wonder if is this something we care about that much.

It does speed up my build a fair bit, but I admit I have a somewhat
uncommon setup.

Oh, I wouldn't question the "speeding up" part.  I simply expected
that people who use separate prefix depending on branch would have
separate checkout for these branches they build and install
regularly to their own prefixes, so recompilation due to prefix
change would not be an issue, because by definition in such a set-up
you won't change branch in a checkout.

Yeah, I think that would be nicer overall. If we move to a link-time
dependency, then we can even put _all_ of the Makefile-based strings in
there without ever having to care about who uses it. Of course, it won't
work for things that truly need to be preprocessor macros (for
conditional compilation), so we'd still be stuck with those (most of
them just end up in CFLAGS and trigger a full rebuild, which is probably
OK).

Yeah, I didn't go through the list of Make variables to see how much
damage I was talking about ;-).