Libguestfs - Jul 2022 - [nbdkit PATCH] tests: Better quoting for cleanup_fn

On Tue, Jul 26, 2022 at 07:13:41AM +0200, Laszlo Ersek
wrote:
> On 07/25/22 16:02, Eric Blake wrote:
> > +    for (( _i = 0; _i < $_cleanup_hook_count; ++_i )); do
> > +        local -n _hook=_cleanup_hook$_i
> > +        "${_hook[@]}"
> 
> BTW, "nameref" variables seem like a relatively new addition to
bash;
> for example RHEL7 does not have them. Interestingly, the RHEL7 manual
> also does not document a nameref-like construct that *does* work in
> RHEL7, namely:
> 
> $ bar=foo
> $ baz=bar
> $ echo ${!baz}
> foo
Indeed it doesn't work on RHEL 7, eg:

$ make && make -C tests check TESTS=test-eflags.sh

leaves tests/eflags.{err,out} around.

Do you have a patch for this?

[...]
> I wonder if the bash release notes mention "nameref" as a more
flexible
> version of "indirect expansion"... Hm, nameref was new in
bash-4.3
> <https://lwn.net/Articles/589566/>, and RHEL7 has
bash-4.2.46-35.el7_9,
> so the lack of "nameref" is understandable (not that it matters
for
> upstream nbdkit :)); indirect expansion is not mentioned however as a
> similar feature.
Actually I'd like to keep things working on RHEL 7 if possible.  It's
still a widely used RHEL release.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
Fedora Windows cross-compiler. Compile Windows programs, test, and
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On 07/26/22 10:11, Richard W.M. Jones wrote:
> On Tue, Jul 26, 2022 at 07:13:41AM +0200, Laszlo Ersek wrote:
>> On 07/25/22 16:02, Eric Blake wrote:
>>> +    for (( _i = 0; _i < $_cleanup_hook_count; ++_i )); do
>>> +        local -n _hook=_cleanup_hook$_i
>>> +        "${_hook[@]}"
>>
>> BTW, "nameref" variables seem like a relatively new addition
to bash;
>> for example RHEL7 does not have them. Interestingly, the RHEL7 manual
>> also does not document a nameref-like construct that *does* work in
>> RHEL7, namely:
>>
>> $ bar=foo
>> $ baz=bar
>> $ echo ${!baz}
>> foo
> 
> Indeed it doesn't work on RHEL 7, eg:
> 
> $ make && make -C tests check TESTS=test-eflags.sh
> 
> leaves tests/eflags.{err,out} around.
> 
> Do you have a patch for this?
This should work:

local hook=_cleanup_hook$_i
eval "\${${hook}[@]}"

Thanks
Laszlo
> 
> [...]
>> I wonder if the bash release notes mention "nameref" as a
more flexible
>> version of "indirect expansion"... Hm, nameref was new in
bash-4.3
>> <https://lwn.net/Articles/589566/>, and RHEL7 has
bash-4.2.46-35.el7_9,
>> so the lack of "nameref" is understandable (not that it
matters for
>> upstream nbdkit :)); indirect expansion is not mentioned however as a
>> similar feature.
> 
> Actually I'd like to keep things working on RHEL 7 if possible. 
It's
> still a widely used RHEL release.
> 
> Rich.
>

On Tue, Jul 26, 2022 at 09:11:24AM +0100, Richard W.M. Jones
wrote:
> On Tue, Jul 26, 2022 at 07:13:41AM +0200, Laszlo Ersek wrote:
> > On 07/25/22 16:02, Eric Blake wrote:
> > > +    for (( _i = 0; _i < $_cleanup_hook_count; ++_i )); do
> > > +        local -n _hook=_cleanup_hook$_i
> > > +        "${_hook[@]}"
> > 
> > BTW, "nameref" variables seem like a relatively new addition
to bash;
> > for example RHEL7 does not have them. Interestingly, the RHEL7 manual
> > also does not document a nameref-like construct that *does* work in
> > RHEL7, namely:
> > 
> > $ bar=foo
> > $ baz=bar
> > $ echo ${!baz}
> > foo
> 
> Indeed it doesn't work on RHEL 7, eg:
> 
> $ make && make -C tests check TESTS=test-eflags.sh
> 
> leaves tests/eflags.{err,out} around.
> 
> Do you have a patch for this?
This might work, although I'm not sure if the eval is safe ...

diff --git a/tests/functions.sh.in b/tests/functions.sh.in
index 82f284a..ab44128 100644
--- a/tests/functions.sh.in
+++ b/tests/functions.sh.in
@@ -88,8 +88,8 @@ _run_cleanup_hooks ()
     echo $0: run cleanup hooks: exit code $_status
 
     for (( _i = 0; _i < $_cleanup_hook_count; ++_i )); do
-        local -n _hook=_cleanup_hook$_i
-        "${_hook[@]}"
+        local _hook=_cleanup_hook$_i
+        eval "\${$_hook[@]}"
     done
 
     exit $_status


Rich.
> [...]
> > I wonder if the bash release notes mention "nameref" as a
more flexible
> > version of "indirect expansion"... Hm, nameref was new in
bash-4.3
> > <https://lwn.net/Articles/589566/>, and RHEL7 has
bash-4.2.46-35.el7_9,
> > so the lack of "nameref" is understandable (not that it
matters for
> > upstream nbdkit :)); indirect expansion is not mentioned however as a
> > similar feature.
> 
> Actually I'd like to keep things working on RHEL 7 if possible. 
It's
> still a widely used RHEL release.
> 
> Rich.
> 
> -- 
> Richard Jones, Virtualization Group, Red Hat
http://people.redhat.com/~rjones
> Read my programming and virtualization blog: http://rwmj.wordpress.com
> Fedora Windows cross-compiler. Compile Windows programs, test, and
> build Windows installers. Over 100 libraries supported.
> http://fedoraproject.org/wiki/MinGW
> _______________________________________________
> Libguestfs mailing list
> Libguestfs at redhat.com
> https://listman.redhat.com/mailman/listinfo/libguestfs
-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://libguestfs.org