_Unwind_FindEnclosingFunction vs darwin

Sun Dec 20 12:14:00 GMT 2009

On Sun, Dec 20, 2009 at 2:02 AM, Jack Howarth <howarth@bromo.med.uc.edu> wrote:
> Bryce,
>  This approach seems cleaner to me...
>> Index: libgcc/config/t-slibgcc-darwin
> ===================================================================
> --- libgcc/config/t-slibgcc-darwin      (revision 155366)
> +++ libgcc/config/t-slibgcc-darwin      (working copy)
> @@ -24,7 +24,7 @@
>>  SHLIB_MKMAP = $(gcc_srcdir)/mkmap-flat.awk
>  SHLIB_MKMAP_OPTS = -v leading_underscore=1
> -SHLIB_MAPFILES += $(gcc_srcdir)/libgcc-std.ver
> +SHLIB_MAPFILES += $(gcc_srcdir)/libgcc-std.ver $(gcc_srcdir)/libgcc-darwin10.ver
>>  # we're only going to build the stubs if the target slib is /usr/lib
>  # there is no other case in which they're useful in a live system.
> Index: gcc/unwind-dw2-fde-darwin.c
> ===================================================================
> --- gcc/unwind-dw2-fde-darwin.c (revision 155366)
> +++ gcc/unwind-dw2-fde-darwin.c (working copy)
> @@ -273,3 +273,15 @@
>                                          the_obj_info);
>   return ret;
>  }
> +
> +void *
> +_darwin10_Unwind_FindEnclosingFunction (void *pc)
> +{
> +  struct dwarf_eh_bases bases;
> +  const struct dwarf_fde *fde = _Unwind_Find_FDE (pc-1, &bases);
> +  if (fde)
> +    return bases.func;
> +  else
> +    return NULL;
> +}
> +
> Index: libjava/include/posix.h
> ===================================================================
> --- libjava/include/posix.h     (revision 155366)
> +++ libjava/include/posix.h     (working copy)
> @@ -56,6 +56,11 @@
>  #define _Jv_platform_solib_suffix ".so"
>  #endif
>> +#if defined(__APPLE__) && defined(__MACH__)
> +#undef _Unwind_FindEnclosingFunction
> +#define _Unwind_FindEnclosingFunction(PC) _darwin10_Unwind_FindEnclosingFunction(PC)
> +#endif
> +
>  // Some POSIX systems don't have O_SYNC and O_DYSNC so we define them here.
>  // Needed in java/io/natFileDescriptorPosix.cc.
>  #if !defined (O_SYNC) && defined (O_FSYNC)
>> with a newly created file gcc/libgcc-darwin10.ver containing _darwin10_Unwind_FindEnclosingFunction.
> This has the advantages of...
>> 1) Not duplicating as much code.
> 2) Being easier to maintain when the duplicated code needs to be synchronized with
> new changes to the original routines.
> 3) Allowing for other sections of gcc to utilize the restored calls as well
> as providing an mechanism to easily restore additional calls from FSF libgcc
> that have been silently nooped by Darwin10.

I thought the plan was to put _Unwind_FindEnclosingFunction into
libgcj, and call _Unwind_Find_FDE instead. But, if that doesn't work
or the libgcc/darwin folks think this approach is a better idea, then
it is fine.
Either way, put the posix.h code inside a static inline _Jv_...
function rather than overriding the function name directly.
Bryce