On 03/22/2011 10:01 PM, H.J. Lu wrote:
>>> Will there be a case where 2 copies of unwind-dw2.c are within the same
>>> process?
>>
>> Sure, that's easy. I think what you are really asking is: will there be
>> a case where we could call functions from one copy and then pass the
>> context to the functions from a different copy. I don't know the answer
>> to that, but it doesn't seem impossible.
It really shouldn't be, but judging from the existance of
_Unwind_IsExtendedContext
it appears that it really is. Which, frankly, I assume is some sort of strange
packaging problem between glibc and libgcc_s.so.
Jakub, do you recall anything more specific about this?
2007-01-03 Jakub Jelinek <ja...@redhat.com>
* unwind-dw2.c (SIGNAL_FRAME_BIT, EXTENDED_CONTEXT_BIT): Define.
(struct _Unwind_Context): Rename args_size to flags, remove
signal_frame field, add a new args_size field and version field.
(_Unwind_IsSignalFrame, _Unwind_SetSignalFrame,
_Unwind_IsExtendedContext): New inline functions.
(_Unwind_GetGR, _Unwind_SetGR, _Unwind_GetGRPtr, _Unwind_SetGRPtr):
Assume by_value array is only present if _Unwind_IsExtendedContext.
(_Unwind_GetIPInfo, execute_cfa_program, uw_frame_state_for): Use
_Unwind_IsSignalFrame.
...
> Then. will this be acceptable?
No.
Ideally we'd remove the by_value array, but I guess that's now versioned
so it'll have to stay even though unused.
Add a new
_Unwind_Word data[DWARF_FRAME_REGISTERS+1];
at the end. Increment the context version number. If the version is
sufficiently high, implement _Unwind_SetGRValue via
context->data[index] = val;
context->reg[index] = &context->data[index];
and do not set by_value at all.
r~
