Re: GNU Make on Linux Feeding All Commands Through ksh

[David Boyce]

On Wed, Oct 8, 2008 at 4:13 PM, Steve Waltner <address@hidden> wrote:
> I'm not following what your asking in your second paragraph. It sounds like
> you're suspecting that our Solaris build of GNU make possibly has /bin/ksh
> as the internal SHELL instead of /bin/sh. I don't believe that is true. In
> the following output ictgrid004 is a Solaris box and ictgrid005 is the Linux
> box...

For the record - though this seems to be a false trail - that's not
_exactly_ what I'm saying. GNU make always[1] uses the "system shell"
by default, and on Unix the system shell is always the binary found at
/bin/sh. POSIX requires the system shell to have ksh-like semantics
but compatibility requires it to have traditional Bourne-shell
semantics. Thus, some Unices support two methods of installation: the
traditional/compatible one which everyone uses and the
POSIX-conformant one which nobody uses except when passing the POSIX
test suite. The latter replaces the Bourne shell at /bin/sh with a
POSIX version which is based on ksh. The shell in question is not
actually /bin/ksh but /usr/xpg4/bin/sh since /usr/xpg4/bin is where
POSIX-conformant-but-not-backward-compatible utilities are stored.
However, /usr/xpg4/bin/sh is just a variant of /bin/ksh which has its
own backward-compatibility issues.

[1] Of course, since it's open source, there's always the possibility
of making your own custom version but we will assume that didn't
happen.

Anyway, I was suggesting that your /bin/sh might be a link to
/usr/xpg4/bin/sh which would have given you, inadvertently, ksh-like
behavior from the system shell on Solaris. But that appears not to be
the case. And I don't know for sure that Solaris supports the "POSIX
install" anyway.

Still, the ball is in your court to figure out how GNU make could
possibly be skipping the shell when SHELL has been overridden since it
just doesn't do that. My best guess is that you aren't really using
GNU make on Solaris (I happen to know that Sun make is not as smart
about SHELL overrides, having reported it as a bug years ago only to
be ignored). Try "make --version" and see what it says. My money says
the problem is a make-compatibility one.

Another thing to consider is to just strip out the SHELL override on
Linux (or everywhere if that works). Solaris /bin/sh is very old so
there's a good chance SHELL was promoted to ksh only to work around a
bug or limitation in it. Linux /bin/sh is really a link to bash which
is 15-20 years newer and has a great deal of ksh compatibility built
in [2], so it might "just work" without the override.

[2] However, note that bash runs in a Bourne-compatible mode when used
as /bin/sh which means some features are not available.

One other thing: if you are really going wth GNU make across the
board, as opposed to the native make, you should assign SHELL (and
most other variables) with the := syntax e.g. "SHELL := /bin/ksh".
This is more efficient but a GNU-only feature.

David Boyce