"Ulrich Weigand" <uweig...@de.ibm.com> writes: > Ian Lance Taylor wrote: >> Andrew Pinski <pins...@gmail.com> writes: >> > On Tue, Mar 22, 2011 at 9:42 AM, Ian Lance Taylor <i...@google.com> wrote: >> >> >> >> Any target on which _Unwind_Word is larger than void * is broken today, >> >> so I don't think we need to care about that case. >> > >> > So a MIPS N32 is broken? Lots of people use that target already and >> > nothing like this has showed up yet. >> >> That is a fair question. It does seem to me that it must be broken in >> some cases. _Unwind_GetGRPtr will return &context->reg[index], which is >> a void** cast to void*. We will then pass that to _Unwind_SetGRPtr. If >> we later call _Unwind_SetGR on that register, it will write a value of >> size _Unwind_Word through that pointer. Similarly if we call >> _Unwind_GetGR, it will read a value of size _Unwind_Word. In both >> cases, we will be accessing a 4-byte field as an 8-byte value. >> >> If MIPS N32 works today, then something must be ensuring that that >> sequence can never occur, or that for some reason it never matters. > > Well, the whole problem only occurs when using the "by value" mechanism, > which is only triggered by DW_CFA_val_... CFI statements, which are new > in Dwarf-3 and seem to be very rarely used: they are apparently never > generated by GCC, and the only files I could find in current glibc that > create such CFI by hand are Intel-specific.
I see, thanks. H.J., what is the failure mode that you are seeing? This suggests that, at least, when sizeof(_Unwind_Word) > sizeof(void*), we need to extend _Unwind_Context with a new array at the end, and use that new array when by_value[REG] is true. Ian
