[cfe-commits] r164992 - /cfe/trunk/Makefile

[Bill Wendling]

On Oct 2, 2012, at 11:49 AM, David Blaikie <dblaikie at gmail.com> wrote:

> On Tue, Oct 2, 2012 at 11:39 AM, Bill Wendling <isanbard at gmail.com> wrote:
>> On Oct 2, 2012, at 11:35 AM, David Blaikie <dblaikie at gmail.com> wrote:
>> 
>>> On Mon, Oct 1, 2012 at 11:19 PM, Bill Wendling <isanbard at gmail.com> wrote:
>>>> Author: void
>>>> Date: Tue Oct  2 01:19:15 2012
>>>> New Revision: 164992
>>>> 
>>>> URL: http://llvm.org/viewvc/llvm-project?rev=164992&view=rev
>>>> Log:
>>>> Use an environment variable instead of what's in the make cmd goals.
>>> 
>>> Still makes me sad that this is an environment variable (admittedly
>>> this isn't important - just an aesthetic issue for me)
>> 
>> I know. I tried to make it work, but couldn't. The thing is that clang is built with MAKECMDGOALS == all, and not 'clang-only', which I would prefer.
> 
> Where's that MAKECMDGOALS value coming from? just the LLVM build
> invoking the Clang build?
> 
It's set automatically by the 'make' program. So if you do this:

	make fnord

the MAKECMDGOALS will be 'fnord'. When we build clang it's set to 'all' because that's how the whole build system seems to work...

>> So I had to default to making it a variable. :-(
>> 
>>> - what's the
>>> use case for this? It just seems like this should naturally fall out
>>> from any build command that wants to just build clang. If it doesn't
>>> then someone may get sub-optimal builds because they don't know about
>>> this environment variable they need to use.
>> 
>> This is for building clang with LTO and wanting only the clang and clang++ executables and libraries (no tools, etc.). The problem here is that LTO takes a *long* time to link things because of how much memory it takes. Building anything extraneous is a waste here.
> 
> Yeah, I figured it was something like that - my point was that while
> it's a big waste for this case, it's a small waste for every other
> user that wants to just build the Clang installation binaries &
> doesn't use this flag.
> 
True. But they don't need to know about the flag. :) Here's the code in the top-level Makefile:

ifeq ($(MAKECMDGOALS),clang-only)
  BUILD_CLANG_ONLY := YES
  DIRS := $(filter-out tools docs unittests, $(DIRS)) \
          tools/clang tools/lto
  OPTIONAL_DIRS :=
endif

>> What I did is link this environment variable with the 'clang-only' flag (see equivalent patch on llvm-commits). When someone specifies 'make clang-only', they won't get the other stuff.
> 
> Hmm, OK - I'm not quite sure how that works just looking at the LLVM
> Makefile, but I'll keep an eye out for the patch as I work through my
> email backlog. If it does the right thing for any LLVM make target
> then I can't complain too much - just a minor implementation wart at
> that point.
> 
I forgot to check the code in. (>.<) It's there now.

-bw