On 01/11/2012 12:43 AM, Torvald Riegel wrote:
>> One could steal code from bohem-gc for this.
>> See GC_get_stack_base in os_dep.c.
>
> Thanks for the pointer. I looked at this code, and it seems fairly
> complex given the dependencies on OS/libc and OS/libc behavior. From a
> maintenance point-of-view, does it make sense to copy that complexity
> into libitm? boehm-gc is used in GCC, so perhaps that's not much of a
> problem, however. I also looked at glibc's memcpy implementations, and
> copying those plus a simple byte-wise copy for the generic case could be
> also a fairly clean solution.
> Also, is the license compatible with the GPL wrt. mixing sources?
>From the maintenance point of view, I do think it makes sense to copy.
As for the license, I expect we'd want to copy into a separate file so
that we can keep things vaguely separated.
> What about keeping the patch/hack that I posted for now, creating a PR,
> and looking at this again for another release?
I suppose that's not unreasonable. Ok with...
> +static inline void *
> +mask_stack_bottom(gtm_thread *tx)
> +{
> + return (uint8_t*)__builtin_dwarf_cfa() - 128;
> +}
Not only can this not be inline, it must be out-of-line. Otherwise you're not
including the stack frame of gtm_undolog::rollback much less memcpy. You could
get this result inline if you specialized for the arch by looking at the hard
stack pointer register, but __builtin_dwarf_cfa is at the wrong end of the
stack.
You might as well make the fudge factor a lot larger. Like 4-8k.
> + if (likely(ptr > top || (uint8_t*)ptr + len <=bot))
Missing space before "bot".
r~
