Re: [E-devel] Crash using C++ Layout signal API

Cedric Bail <[email protected]> Wed, 23 Jun 2021 22:41:02 +0000

Newsgroups	gmane.comp.window-managers.enlightenment.devel
Message-ID	<I_hl8aKk_-ed_NY7h334ZigQ3qcqZcyuIXrfLi-h2BBFNJnoLpTqlfMWhavB51Q5rJEuoHWIVW4ebYC2AQVIaR4Bp5TgXaogXdbhTp9PF0A=@ddlm.me>

On Wednesday, June 23rd, 2021 at 3:53 PM, Andreas Volz <[email protected]> wrote:
> Am 23.06.21 um 18:02 schrieb Cedric Bail:
> > On Tuesday, June 22nd, 2021 at 11:36 PM, Andreas Volz [email protected] wrote:
> > > Hello together,
> > 

> > > after some waiting time I would like to ask here if some other user
> > > could at least verify the same crash with C++ API that I described here:
> > 

> > > https://phab.enlightenment.org/T8943
> > 

> > > If I'm not strongly misusing the API than it's a very basic error. Just
> > > loading an Edje file into a Layout.
> > 

> > I vaguely remember discussion about this issue. I don't think we actually support function pointer in auto generated code, except for eo callback mechanism, due to some memory lifecycle uncertainty. And it kind of match what your bug report says.
> > 

> > > Would be good to know someone else does see the same.
> > > Do you know a workaround to come around this? Maybe use another C++
> > > compatible API / mix with C API to continue work on my application?
> > > regards
> > 

> > I remember that the workaround would be to switch to use the C API instead of the C++ one as I think we do have a smart pointer trick that allow you to directly use the C pointer and C function from the C++ object.
> 

> To make it explicit as question. You suggest to not use the C++ API at
> all in my application or just not for this use case?

Not use the C++ API that does take a function as a parameter except for
efl_event.

> Is it a good idea to mix usage of C and C++ API as long as it's not
> fully stable and then adapt later to full C++ usage? Do you know an
> example how to access the C API object?

The C++ API is header only, directly use the C API under it and the
this pointer of a C++ object is actually the Eo* resulting in no
overhead and no ABI in using the C++ binding. It does also means you
can safely go from C to C++ and back. When I played with it last time
you could just pass a C++ Eo object to a C function and the cast
would be done magically. If it isn't done magically anymore, I think
there is a _eo_ref() on the C++ object to get the Eo* pointer.

Cedric

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