[vlc-devel] [PATCH] libvlc: dump object names that are leaking

[Thomas Guillem]

On Wed, Jun 7, 2017, at 19:23, David Fuhrmann wrote:
> 
> > Am 07.06.2017 um 11:34 schrieb Thomas Guillem <thomas at gllm.fr>:
> > 
> > In case of a vlc_object_t leak, and if asserts are enabled, the error output
> > will be like the following:
> > 
> > === vlc_object LEAKS detected ===
> >  | art finder
> >  | meta fetcher
> >  | input
> >  |   \ input source
> >  |   |   \ demux meta
> >  |   |   | demux
> >  |   |   | stream
> >  |   |   |   \ stream
> > ---
> > src/libvlc.c | 28 ++++++++++++++++++++++++++++
> > 1 file changed, 28 insertions(+)
> > 
> > diff --git a/src/libvlc.c b/src/libvlc.c
> > index 4b220d2e31..45b0dd14d1 100644
> > --- a/src/libvlc.c
> > +++ b/src/libvlc.c
> > @@ -554,6 +554,22 @@ void libvlc_InternalCleanup( libvlc_int_t *p_libvlc )
> > #endif
> > }
> > 
> > +#ifndef NDEBUG
> > +static void DumpObjectLeaks(vlc_object_internals_t *priv, unsigned level)
> > +{
> > +    bool first = true;
> > +    for (priv = priv->first; priv != NULL;  priv = priv->next)
> > +    {
> > +        vlc_object_t *obj = vlc_externals(priv);
> > +        for( unsigned i = 0; i < level; i++ )
> > +            fprintf( stderr, "  %s ", first && i == level -1 ? "\\" : "|" );
> > +        fprintf( stderr, "%s\n", obj->obj.object_type );
> > +        DumpObjectLeaks( priv, level + 1 );
> > +        first = false;
> > +    }
> > +}
> > +#endif
> > +
> > /**
> >  * Destroy everything.
> >  * This function requests the running threads to finish, waits for their
> > @@ -567,6 +583,18 @@ void libvlc_InternalDestroy( libvlc_int_t *p_libvlc )
> > 
> >     vlc_ExitDestroy( &priv->exit );
> > 
> > +#ifndef NDEBUG
> > +    {
> > +        vlc_object_internals_t *priv = vlc_internals(p_libvlc);
> > +        if( atomic_load( &priv->refs ) != 1 )
> > +        {
> > +            vlc_mutex_lock( &priv->tree_lock );
> > +            fprintf( stderr, "=== vlc_object LEAKS detected ===\n" );
> > +            DumpObjectLeaks( priv, 1 );
> > +            vlc_mutex_unlock( &priv->tree_lock );
> > +        }
> > +    }
> > +#endif
> >     assert( atomic_load(&(vlc_internals(p_libvlc)->refs)) == 1 );
> >     vlc_object_release( p_libvlc );
> > }
> > -- 
> 
> Hi,
> 
> I would find such an addition quite helpful. Getting the information from
> a debugger was very complex last time I tried.
> So I would say add this as an additional helper.

Indeed, there is no leak sanitizer on macPs (there is asan but without
the leak feature).
It's always possible to attach a debugger and navigate through the list
of objects, but this is not as convenient as having the objects
displayed directly when the program crash. Furthermore, you can't attach
a debugger on every devices, there is some hardware constructors on
Android (like Samsung) that prevent to attach gdb to a process.

> 
> BR. David
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