Hi Gábor,
On Wed, 17 Oct 2018, SZEDER Gábor wrote:
> On Tue, Oct 16, 2018 at 03:40:01PM -0700, Jonathan Nieder wrote:
> > SZEDER Gábor wrote:
> > > On Tue, Oct 16, 2018 at 02:54:56PM -0700, Jonathan Nieder wrote:
> > >> SZEDER Gábor wrote:
> >
> > >>> Our Makefile has lines like these:
> > >>>
> > >>> CFLAGS = -g -O2 -Wall
> > >>> CC = cc
> > >>> AR = ar
> > >>> SPATCH = spatch
> > [...]
> > >>> I'm not sure what to do. I'm fine with updating our 'ci/' scripts to
> > >>> explicitly respect CC in the environment (either by running 'make
> > >>> CC=$CC' or by writing $CC into 'config.mak'). Or I could update our
> > >>> Makefile to use '?=' for specific variables, but:
> > >>
> > >> That's a good question. I don't have a strong opinion myself, so I
> > >> tend to trust larger projects like Linux to have thought this through
> > >> more, and they use 'CC = cc' as well.
> > >
> > > I don't think Linux is a good example to follow in this case, see e.g.
> > > 6d62c983f7 (Makefile: Change the default compiler from "gcc" to "cc",
> > > 2011-12-20) (in short: Git is supposed to be buildable with compilers
> > > other than GCC as well, while Linux not really, so they can hardcode
> > > 'CC = gcc').
> >
> > Nowadays Linux builds with clang as well. People also have other
> > reasons to override the CC setting (cross-compiling, etc) and to
> > override other settings like CFLAGS.
> >
> > > Also, the projects I have on hand usually have 'CC = gcc' hardcoded in
> > > their Makefiles, too, but those Makefiles were generated by their
> > > ./configure script (which in turn by ./autogen.sh...), and those tend
> > > to write CC from the environment into the generated Makefiles.
> >
> > Yes, I think that's what makes travis's setup normally work. It makes
> > sense to me since ./configure is expected to have more implicit or
> > automatic behavior. For "make", I kind of like that it doesn't depend
> > on environment variables that I am not thinking about when debugging a
> > reported build problem.
> >
> > When building Git without autoconf, the corresponding place for
> > settings is config.mak. Would it make sense for the ci scripts to
> > write a config.mak file?
>
> A first I though it doesn't, but it turns out it acually does.
>
> 'ci/run-build-and-tests.sh' basically runs:
>
> make
> make test
>
> I naively put a 'CC=$CC' argument at the end of the first command,
> thinking it should Just Work... but then that second 'make test' got
> all clever on me, said "* new build flags", and then proceeded to
> rebuild everything with the default 'cc'. (With the additional
> complication, that on Travis CI we actually run 'make --quiet test',
> which rebuilds everything, well, quietly... so the rebuild itself is
> not even visible in the build logs.)
>
> So, then it's either 'config.mak', or passing a 'CC=$CC' argument to
> _all_ make commands, including those that are not supposed to build
> anything, but only run the tests. I find the latter aesthetically not
> particularly pleasing.
How about using `MAKEFLAGS`? I ran a quick test:
MAKEFLAGS='CC=blub' make -C .. git.o
make: Entering directory '/usr/src/git/wip'
* new build flags
CC git.o
/bin/sh: blub: command not found
In other words, you could add something like this to the ci/ script:
MAKEFLAGS="${MAKEFLAGS:+$MAKEFLAGS }CC=$CC"
export MAKEFLAGS
Ciao,
Dscho
