Re: [PATCH] Teach Makefile to respect external variables: CFLAGS and others.

From: Junio C Hamano <gitster@pobox.com>
Date: Jun 13, 2007, 07:39 UTC
Message-ID: <7vhcpcfglr.fsf@assigned-by-dhcp.pobox.com>
In-Reply-To: <20070613071514.GP86872@void.codelabs.ru>

Eygene Ryabinkin <rea-git@codelabs.ru> writes:

Show 22 quoted lines

> Junio, Sam, good day.
>
> Tue, Jun 12, 2007 at 11:07:56PM -0700, Junio C Hamano wrote:
>> I run "make CFLAGS=-O0 -g" all the time.  Also "make CC=echo"
>> seems to "work" as expected ;-).
>> 
>> Care to elaborate what problem you are trying to solve?
>
> As Sam Ravnborg kindly pointed out, you're using make variables
> and I am trying to give the respect to the environment variables.
>
> And the real problem is that one (for example, me) can try to
> build Git with the different compiler than CC (gccX or icc, for
> example).  And it is much better for lazy people to do 'export
> CC=whatever' once and then fire make any number of times ;))
>
> Answering Sam: yes, with my patch it is easier to inherit the
> variables from the environment.  But it is not clear if it is
> good or bad ;))
>
> But anyway, this patch is only my suggestion, and it can be
> thrown away :)

Oh, I will, very gladly ;-), as it is obviously inferior than how we currently do our build.

I would personally hate environment affecting build (or anything for that matter), as it makes it unnecessarily difficult to diagnose when something goes wrong. I consider that it is a beautiful thing that make can take explicit override from the command line.

Lazy people like me can always have a make wrapper. E.g. I have a checkout of my 'todo' branch at Meta in git.git repository, so I would say

	$ Meta/Make -pedantic

to ask for specific set of CFLAGS. If something goes wrong and I need to ask for help from other people, it is crystal clear to them that I am using something "customized" from the above command line.

If you modify Makefile to allow the build procedure to be easily contaminated with stray environment, and when your build breaks, you would answer that your command line is:

	$ make

when asked how you tried to build things -- and leave people who try to help you scratching their head, wasting their time.