[Libguestfs] [PATCH libnbd] tests: Use libc_malloc_debug.so.0 instead of MALLOC_CHECK_ for glibc 2.34

[Eric Blake]

On Tue, Aug 24, 2021 at 05:13:24PM +0100, Richard W.M. Jones wrote:
> This is the nbdkit change transplanted to libnbd.  Because there are
> several subdirectory Makefiles which define the MALLOC_CHECK_
> environment variables, I turned it into a macro which is placed in the
> top level subdir-rules.mk.

Nice refactoring to avoid duplication.

> 
> Note this currently breaks valgrinding because of:
> https://sourceware.org/bugzilla/show_bug.cgi?id=28256
> and because there's not a good place to unset GLIBC_TUNABLES in libnbd.

Patch looks good to apply (I almost tackled the same project myself
before seeing your email).  Could we modify run.in to define _VG to
start with 'env -u GLIBC_TUNABLES valgrind' on systems where 'env -u'
is supported? (Sadly, POSIX doesn't require 'env -u')

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org