Re: [Qemu-devel] [PATCH 07/10] roms: build edk2 firmware binaries and variable store templates

[Eric Blake]

On 3/12/19 10:15 AM, Laszlo Ersek wrote:

> I'm acutely aware of portable vs. non-portable shell scripts. While
> working on the code, I specifically checked that "local" was not
> specified in SUSv4. The point is, I didn't care, because I didn't target
> a POSIX system, but a GNU system.
> 
> We already require GNU Make, to my knowledge. Perhaps not by decree, but
> through the feature set that we use.

Indeed, qemu fails to build under BSD make.

> I really want to keep "local", as it keeps the shell variable namespace
> clean. Regarding the functions that I did put in the "global namespace",
> I was careful to prefix them suitably.

Yes, using local makes bash functions easier to write. (And I've been
trying to argue that POSIX should adopt local, but there is a
fundamental difference between ksh local (static scoping) and bash local
(dynamic scoping) that neither shell is willing to switch their existing
practice to meet at common ground - which is why POSIX hasn't
standardized anything yet)

> 
> IMO, it's perfectly fine to require the shell to be bash here, given
> that this feature is meant for a subset of maintainers (and not for
> end-users), and that building edk2 already requires a quite sizeable set
> of packages installed (such as nasm, iasl, ...) So this feature is not
> meant for any random POSIX system.
> 
> What I did miss in fact was that "GNU Make" didn't imply "/bin/bash":

Yep, I can see how that was not obvious, and I also agree that:

> Thus, the real fix here is to be explicit about the bash requirement. I
> should add
> 
>   SHELL=/bin/bash
> 
> near the top of "Makefile.edk2".

this should indeed force the use of bash for all shell snippets and
$(shell) invocations in that makefile (and let you get away with
'source' instead of '.', as well as the use of 'local' within the
sourced functions).

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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