Re: [Flightgear-devel] Segmentation fault acquiring SGPropertyLock

[TheFGFSEagle <the...@gm...>]

Uh, I didn't remove any asserts - I had pulled current next SG and FG and
just ran cmake --build . && cmake --install . !

Am Di., 18. Juli 2023 um 11:59 Uhr schrieb Julian Smith <ju...@op...>:

> On Tue, 18 Jul 2023 11:18:22 +0200
> Florent Rougon <f.r...@fr...> wrote:
>
> > Hi,
> >
> > Julian Smith <ju...@op...> wrote:
> >
> > > This diff seems to fix things for me:
> >
> > Many thanks, same here!
> >
> > > The problem was that tiedProperties.Tie() was calling
> > > FGProperties::setFreeze(true) before it returned, but we were only
> setting
> > > _simFreezeNode *after* tiedProperties.Tie() had returned.
> >
> > Indeed, TiedPropertyList::Tie() calls SGPropertyNode::tie()
> > (simgear/simgear/props/props.cxx:4217) which, when the “useDefault” arg
> > is true which is the case here, does setValue(exclusive, old_val) which,
> > in the case at hand, calls the setter method FGProperties::setFreeze().
> > As you explained, this executes _simFreezeNode->fireValueChanged() but
> > _simFreezeNode hasn't been set at this point yet.
> >
> > > tiedProperties.Tie() simply returns the node that it was given as its
> > > first arg, so the diff simply sets _simFreezeNode to the value it would
> > > have taken later, before calling tiedProperties.Tie().
> >
> > > Please note that it's entirely possible that i've missed something
> > > subtle here. I haven't considered what's going on in any great detail,
> > > and i've never used tied properties myself.
> >
> > I've read the code of SGRawValueMethods, TiedPropertyList and
> > SGPropertyNode::tie() to understand this but that's about what I know on
> > the subject matter — and nothing about the freeze process per se. Your
> > analysis looks good to me and your patch fixes the crash I reported
> > yesterday.
> >
> > Maybe James will want to double-check, but since he seems to be busy
> > with RL, given the non-invasiveness of your patch and our understanding
> > of this issue, I believe it's pretty safe to commit.
>
> Great, good to know you think it's ok. I've just pushed the fix.
>
> >
> > Thanks & regards
> >
> > P.S.: your patch (the attachment) had all explanations plus your
> >       signature inside (yeah, I know the patch tool tolerates
> >       “trailing, uh... garbage”). :)
>
> I reckon that might be your email client? - i didn't attach the patch,
> just included it inline.
>
> Thanks,
>
> - Jules
>
> --
> http://op59.net
>
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