Re: [PATCH 4/6] backends/: should use size_t n_regs_mapping for *_sample_sp_pc

[Aaron Merey]

Hi Serhei,

On Thu, Apr 9, 2026 at 4:07 PM Serhei Makarov <ser...@serhei.io> wrote:
> On Sun, Apr 5, 2026, at 8:24 PM, Aaron Merey wrote:
> >> @@ -84,8 +84,8 @@ generic_sample_sp_pc (const Dwarf_Word *regs, uint32_t 
> >> n_regs,
> >>    /* TODO: Register locations could be cached and rechecked on a
> >>       fastpath without needing to loop, though the overhead reduction
> >>       is minimal.  */
> >> -  int j, need_sp = (sp != NULL), need_pc = (pc != NULL);
> >> -  for (j = 0; (need_sp || need_pc) && n_regs_mapping > (uint32_t)j; j++)
> >> +  int need_sp = (sp != NULL), need_pc = (pc != NULL);
> >> +  for (size_t j = 0; (need_sp || need_pc) && n_regs_mapping > j; j++)
> >>      {
> >>        if (n_regs < (uint32_t)j) break;
> >
> > This cast will truncate j when size_t is uint64_t, although having
> > more than 2^32 registers is unlikely.
> Agreed, don't see a better way to do this.
> The comparison will be fixed to use <= in the revised patch (cf the 
> discussion on patch1),
> so even in a deliberately-pathological case we would have j reach UINT32_MAX
> and trigger this correctly.

Ack.

Aaron