Re: static class member as interrupt handler works, but not if class is templated

[Anton Staaf <anton@socialhacker.com>]

Klaus, I'm not sure if my previous answer didn't make it through or was
just missed, but I believe your problem is related to this GCC bug:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70435

-Anton


On Mon, Apr 12, 2021 at 5:14 AM Klaus Rudolph <lts-rudolph@gmx.de> wrote:

> Am 12.04.21 um 13:53 schrieb Matthijs Kooijman:
> >>> - figure out, where the special handling of the __vector_10 seems to
> >>> happen, and why it is not happening in the class template case. This
> >>> might help diagnose if and where to fix it within the compiler.
> >>
> >> That is compiler internals... yes, if it is a compiler bug, it is the
> >> way to have a solution. But in that case, it seems to be a generic
> >> problem for gcc as attributes are not assigned to any templated class
> >> member functions. No idea if this is related to the target ( avr ) or
> >> generic for all platforms. But I never did any change inside the
> >> compiler. Any help is welcome!
> >
> > My suspiciou would be that this is a generic gcc problem, where the
> > "asm" attribute is not honoured for template functions. It probably also
> > makes some sense, since a template is intended to be instantiated
> > multiple times, and each instantiation gets a name that is generated
> > based on (I believe) the template arguments passed, so I suspect that
> > the "generate a name for this template instantiation" code doesn't look
> > at the asm attribute.
> >
> > Also note that *if* it would, then each instantiation would use the same
> > name and multiple instanations would result in duplicate symbols. If you
> > would bring this up as a gcc bug, I wouldn't be surprised that it would
> > be closed as wontfix for this reason.
>
> I disagree as a template "always" would be instantiated multiple times.
> And even if it would be, the linker will fire a error message, as it
> sees multiple definitions. So there is no "general" problem in
> "renaming" a templated function. It simply *can* work.
>
> But it looks that not only the "renaming" stuff did not work, all the
> flags are not handled with the templated function. Looks like that the
> asm declaration did not find its target :-)
>
> >
> > Another workaround that I think hasn't been suggested yet, would be to
> > just define a global `__vector_10` function and from that just call your
> > templated static member.
>
> That is the classical way "we" all work. And it optimizes well in that
> case as the code from the static templated member is fully inlined. But
> it is still a workaround and it simply breaks standard c++ coding. Yes,
> we can write C with classes, but I simply dislike :-)
>
> > Combined with the `always_inline` attribute,
> > you can ensure that the call is inlined and there is no runtime overhead
> > (with LTO, this probably already happens when there's just a single call
> > to the member).
>
> It already optimizes well in O2 if templated member function and free
> handler definition is in same translation unit.
>
> Klaus
>
>
>