bug#40641: Building from git breaks when /bin/sh isn't bash

[elaexuotee]

"pelzflorian (Florian Pelz)" <address@hidden> wrote:
> On Wed, Apr 15, 2020 at 06:06:25PM +0900, elaexuotee--- via Bug reports for 
> GNU Guix wrote:
> > When building from git, ./bootstrap ends up generating (via automake) 
> > several
> > Makefiles that set SHELL = /bin/sh. However, some targets contain rules that
> > make use of bashisms. This leads to breakage when /bin/sh is something other
> > than bash.
> > 
> > In particular, I am building from a foreign distro which links /bin/sh to 
> > dash.
> > Currently, this ends up breaking the build, the details of which I reported
> > to guix-devel in [0].
> 
> <https://bugs.gnu.org/25258> is related.  Your workaround may be more welcome.
> 
> Regards,
> Florian


Florian,

Thanks for the pointer. I ended up doing a little bit of sleuthing and think
I figured out a relatively clean fix---a simple one-liner in configure.ac.
Attached is a proof-of-concept patch against master (974bf81776).

Currently, autoconf sets make's shell to whatever it thinks is best. On a
foreign distribution, this often ends up something external to guix profile.
However, when this isn't bash, we run into problems.

The patch's idea is to let make use its hard-coded default shell. A guix-built
make will correctly fallback to whichever sh is in the profile, so for `guix
environment guix' this effectively becomes $GUIX_ENVIRONMENT/bin/sh. For
example,

    $ echo '$(info $(SHELL))' | make -f -
    /gnu/store/29jhbbg1hf557x8j53f9sxd9imlmf02a-bash-minimal-5.0.7/bin/sh
    make: *** No targets.  Stop.

I belive this should do the Right Thing. However, is there anything I am
missing? Perhaps this change would break build scenaries I am not thinking of?

Cheers,
B. Wilson

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