qemu build failure, hxtool is a bash script, not a /bin/sh script

[Felix von Leitner]

hxtool (part of the early build process) is a bash script. Running it with /bin/sh yields a syntax error on line 10:

 10 STEXI*|ETEXI*|SQMP*|EQMP*) flag=$(($flag^1))

$(( expr )) is a bash extension, not part of /bin/sh.

Note that replacing the sh in the first line in hxtool with /bin/bash does not help, because the script is run manually from the Makefile with sh:

154 $(call quiet-command,sh $(SRC_PATH)/scripts/hxtool -h < $< > $@," GEN $@")

The fix is to change those lines to

154 $(call quiet-command,bash $(SRC_PATH)/scripts/hxtool -h < $< > $@," GEN $@")

(there are five or so).

[Eric Blake (eblake)]

On 07/23/2014 04:21 AM, Felix von Leitner wrote:
> Public bug reported:
>
> hxtool (part of the early build process) is a bash script. Running it
> with /bin/sh yields a syntax error on line 10:
>
> 10 STEXI*|ETEXI*|SQMP*|EQMP*) flag=$(($flag^1))
>
> $(( expr )) is a bash extension, not part of /bin/sh.

Wrong. $(( expr )) is mandated by POSIX. What system are you on where
/bin/sh is not POSIX? (Solaris is the only platform where /bin/sh does
not try to be POSIX-compliant, but who uses that for qemu?)

What is the actual syntax error you are seeing? Is this a bug in dash
on your distribution? I can't get dash to fail for me on Fedora:

$ dash -c 'f=1; f=$(($f^1)); echo $f'
0
$ dash -n scripts/hxtool; echo $?
0

--
Eric Blake eblake redhat com [phone]
Libvirt virtualization library http://libvirt.org

[Felix von Leitner (felix-launchpad)]

I actually have bash installed as /bin/sh and /bin/bash.
But I also have heirloom sh installed, which installs itself as /sbin/sh, and that happened to be first in my $PATH.

Since the makefiles use "sh script" to run the scripts, that called the heirloom sh.

http://heirloom.sourceforge.net/sh.html

It is, it turns out, derived from OpenSolaris. So there you go :-)

When I delete /sbin/sh, qemu builds.

[Eric Blake (eblake)]

On 07/23/2014 10:13 AM, Felix von Leitner wrote:
> I actually have bash installed as /bin/sh and /bin/bash.
> But I also have heirloom sh installed, which installs itself as /sbin/sh, and that happened to be first in my $PATH.
>
> Since the makefiles use "sh script" to run the scripts, that called the
> heirloom sh.
>
> http://heirloom.sourceforge.net/sh.html
>
> It is, it turns out, derived from OpenSolaris. So there you go :-)
>
> When I delete /sbin/sh, qemu builds.

Then the bug is not in qemu, but in your environment. Installing
known-broken heirloom where it can be found first on a PATH search for
sh is just asking for problems, not just with qemu, but with all SORTS
of programs that expect POSIX semantics from a Linux /bin/sh.

Rather than change the Makefile to invoke the script with bash, we could
instead bend over backwards to rewrite the script in a way that works
with non-POSIX shells (as in, flag=`expr $flag ^ 1`), but that feels
backwards to me. Until someone is actively worried about porting qemu
to a true Solaris environment, rather than just an heirloom-as-/bin/sh
Linux environment, I don't think it's worth the effort.

--
Eric Blake eblake redhat com [phone]
Libvirt virtualization library http://libvirt.org

[Peter Maydell (pmaydell)]

On 23 July 2014 17:31, Eric Blake <email address hidden> wrote:
> Rather than change the Makefile to invoke the script with bash, we could
> instead bend over backwards to rewrite the script in a way that works
> with non-POSIX shells (as in, flag=`expr $flag ^ 1`), but that feels
> backwards to me. Until someone is actively worried about porting qemu
> to a true Solaris environment, rather than just an heirloom-as-/bin/sh
> Linux environment, I don't think it's worth the effort.

My view on this has always been "we shouldn't assume bash,
but we can assume POSIX shell semantics". (And also that
we should assume /bin/sh is a POSIX shell, because it's the
21st century, and Solaris should just get with it :-))

thanks
-- PMM

[Felix von Leitner (felix-launchpad)]

It turns out that expr does not support ^ (at least according to the man page). :-)

Still, you could do expr -$flag + 1 to do the same thing.

Is the ruckus just about this one place where $(( )) is used or are there other non-Bourne-shell constructs?

[Thomas Huth (th-huth)]

Closing this ticket, as it was rather a problem with the non-posix-compliant shell and not the QEMU build system.