Re: FR: Provide Out-Of-Tree Building; Provide Cross-Compile Parameters

From: Eric Sunshine <sunshine@sunshineco.com>
Date: Jul 8, 2024, 19:08 UTC
Message-ID: <CAPig+cTaH+TiD9Ut5Q_BPinqdAirW51J56R_tUTSnL=XGzxvfg@mail.gmail.com>
In-Reply-To: <CALaQ_hr2Hzri6y4KwYOPmGzfvM8EjJpddvLL7CQ=d3H4QLCzJw@mail.gmail.com>

[please avoid top-posting on this mailing list(*)]

On Mon, Jul 8, 2024 at 2:33 PM Nathan Royce <nroycea+kernel@gmail.com> wrote:

Show 10 quoted lines

> Well goodness me, seems I spoke too soon.
> I found the that zlib was required (looking for "zlib.h"), so I built
> that first and that too wasn't all that cross-compile friendly.
> I saw "CHOST" is used, and was surprised that it didn't seem to need
> anything to link against from the target sysroot, so that turned out
> better than I thought it would.
>
> I then used `configure` prefixed with
> the`CFLAGS="--sysroot=<pathToSysroot>"`, along with `HOST_CPU=<tuple>`
> for `make`, and it worked out fine.

The Git build system determines some aspects of the environment dynamically, so if you were cross-compiling for a different architecture, it is possible that this did not enable every feature of Git. For instance, if you look inside `config.mak.uname` and `Makefile`, you will find a number of invocations of $(shell ...) which pluck some host system information at build time rather than at configuration time.

> Before moving it to my device, I just nspawned/chrooted into it and
> `git --help` worked. So looks good and easy steps. Of course, it'll
> depend on whether or not a git function using zlib also passes (hoping
> zlib actually built fine without needing any outside linkage).

A successful `git --help` is one small victory. Running the full test suite on the cross-compiled project will give a more complete picture of whether or not the effort was successful.

> I'd still suggest and prefer that git (and zlib) follows what others
> have settled on doing to be cross-compile-friendly.

I can't speak for the zlib project, but for this to happen in Git, someone with an interest in seeing such an outcome will need to submit patches.

[*] https://lore.kernel.org/all/YQK0JuI1w1zsEHeC@kroah.com/