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[RFC] Improving compatibility of NetBSD's unwind.h (or replacing it?)


While working on building more LLVM projects on NetBSD, I've noticed
that libcxxabi fails to build due to incompatible unwind.h.  The example
of problematic code is [1]:

  _Unwind_SetGR(context, __builtin_eh_return_data_regno(0),
  _Unwind_SetGR(context, __builtin_eh_return_data_regno(1),
  _Unwind_SetIP(context, results.landingPad);

This fails to build because NetBSD's unwind.h expects the last argument
to _Unwind_Set{GR,IP} to be a pointer.  However, it seems that other
implementations expect an unsigned integer type instead.  The types used
for the last argument of appropriate functions (and return type of their
respective _Unwind_Get* counterparts) are:

                        SetGR/GetGR   SetIP/GetIP
  gcc 7.3.0 on Linux    _Unwind_Word  _Unwind_Ptr   (-> unsigned [a])
  clang                 _Unwind_Word  _Unwind_Word  (-> uintptr_t)
  llvm-libunwind        uintptr_t     uintptr_t
  libunwind 1.2.1       uns. long     uns. long

  [a] gcc is doing some __attribute__ magic on top of it

I think changing our header to use unsigned integer type alike other
implementations is the way to go.  Does this sound like the right thing
to do?


Best regards,
Michał Górny

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