Re: _Unwind_FindEnclosingFunction vs darwin

[Bryce McKinlay <bmckinlay at gmail dot com>]

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