[libvirt] [PATCH] tests: link virpcimock with utils

[Daniel P. Berrange]

On Mon, Apr 10, 2017 at 01:18:05PM +0200, Michal Privoznik wrote:
> On 04/10/2017 01:04 PM, Daniel P. Berrange wrote:
> > On Mon, Apr 10, 2017 at 01:00:58PM +0200, Michal Privoznik wrote:
> >> On 04/10/2017 09:52 AM, Pavel Hrdina wrote:
> >>> In virpcimock we use some functions from utils so we should link
> >>> utils library to provide required symbols.
> >>>
> >>> Signed-off-by: Pavel Hrdina <phrdina at redhat.com>
> >>> ---
> >>>  tests/Makefile.am | 3 ++-
> >>>  1 file changed, 2 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/tests/Makefile.am b/tests/Makefile.am
> >>> index 279e9b7da8..8b9bba31ce 100644
> >>> --- a/tests/Makefile.am
> >>> +++ b/tests/Makefile.am
> >>> @@ -1131,7 +1131,8 @@ virpcimock_la_SOURCES = \
> >>>  	virpcimock.c
> >>>  virpcimock_la_CFLAGS = $(AM_CFLAGS)
> >>>  virpcimock_la_LDFLAGS = $(MOCKLIBS_LDFLAGS)
> >>> -virpcimock_la_LIBADD = $(MOCKLIBS_LIBS)
> >>> +virpcimock_la_LIBADD = $(MOCKLIBS_LIBS) \
> >>> +	../src/libvirt_util.la
> >>
> >> You forgot to include $(PROBES_O). But even with that added in, this will
> >> not fly. While you make it work under libvirt it fails without it because
> >> 'stat' is undefined but called. Look into virtestmock.c for explanation.
> >>
> >> I'm not sure how to address this issue. I know about it for quite some time
> >> now but all my previous attempts to fix it (including this one) failed. I've
> >> tried to mimic what virtestmock.c does, but without any luck.
> > 
> > What is the actual build problem with the virpcimock ? It seems to work
> > fine for me right now.
> 
> It does build fine. You want to run it under valgrind:
> 
> libvirt.git/tests $ ../run valgrind --trace-children=yes ./virpcitest
> ==30672== Memcheck, a memory error detector
> ==30672== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
> ==30672== Using Valgrind-3.12.0 and LibVEX; rerun with -h for copyright info
> ==30672== Command: libvirt.git/tests/.libs/virpcitest
> ==30672== 
> valgrind: symbol lookup error: libvirt.git/tests/.libs/virpcimock.so: undefined symbol: virFree
> 
> 
> 
> > 
> > FWIW, the original intenion was that the mock impls should not use any
> > libvirt APIs, just pure POSIX / Linux APIs, so as to avoid dependancies
> > which could end up being circular.
> 
> Yeah, I was just about to suggests this. However, in general would
> it be a problem if a mock library would link with say libvirt_utils
> statically? That way we shouldn't have any dependency problems,
> should we?

Yep, static linking makes you immune from LD_PRELOADs.

The one caveat is about global data & any 3rd party library initialization
though. eg You'd now have 2 copies of any global variables, and if you
trigger code that initializes 3rd party libraries that'd get run twice.

Probably ok if we're only using very simple things like virfile & virstring
but if we get into the more advanced modules it could cause trouble.

Regards,
Daniel
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