Re: [Libunwind-devel] Fix word size for MIPS architecture

[Vicente Olivert Riera]

On 12/02/2014 02:35 AM, Arun Sharma wrote:
> On Mon, Dec 1, 2014 at 6:07 PM, Vicente Olivert Riera
> <address@hidden> wrote:
> 
>> Both n32 and n64 are MIPS64 ABIs. The only difference is that n32 has
>> 32bit pointers and integers, and n64 has 64bit pointers and integers.
>> But both are a MIPS64 architecture.
>>
> 
> This sounds more like:
> http://en.wikipedia.org/wiki/X32_ABI
> 
> We don't have a precedent for this in the code base as far as I know.
> I still think it should be exposed as a new ABI for everything to work
> right (eg: n64 unwinder unwinding a n32 target and vice versa).
> 
> For the specific patch you attached to the bug report, assuming n32
> has 64 bit registers: Changing unw_word_t to 32 bit will break
> interfaces like:
> 
> unw_get_reg (unw_cursor_t *cursor, int regnum, unw_word_t *valp)

Uhm..., I don't think so. Take a look to this:

http://www.imgtec.com/mips/architectures/mips64.asp

The last part:

"[...] the architecture features a 32-bit compatibility mode, in which
all registers and addresses are 32-bit wide [...]"

> Could you solve the X problem by using a different type that
> represents the size of a pointer (Eg: ptrdiff_t or size_t?)
> 
>  -Arun
> 


-- 
Vicente Olivert Riera
Graduate Software Engineer, MIPS Platforms
Imagination Technologies Limited
t: +44 (0)113 2429814
www.imgtec.com