[RFC PATCH v4 02/15] GDB: Use gdb::array_view for buffers used in register reading and unwinding

[Maciej W. Rozycki]

On Fri, 10 Jan 2025, Thiago Jung Bauermann wrote:

> >> diff --git a/gdb/mips-tdep.c b/gdb/mips-tdep.c
> >> index c00efbd02ad0..24970c7637ad 100644
> >> --- a/gdb/mips-tdep.c
> >> +++ b/gdb/mips-tdep.c
> >> @@ -951,14 +951,17 @@ mips_register_to_value (const frame_info_ptr &frame, int
> >> regnum,
> >>
> >>    if (mips_convert_register_float_case_p (gdbarch, regnum, type))
> >>      {
> >> -      get_frame_register (frame, regnum + 0, to + 4);
> >> -      get_frame_register (frame, regnum + 1, to + 0);
> >> +      gdb::array_view<gdb_byte> first_half = gdb::make_array_view (to, 4);
> >> +      gdb::array_view<gdb_byte> second_half = gdb::make_array_view (to + 4, 4);
> >>
> >> -      if (!get_frame_register_bytes (next_frame, regnum + 0, 0, { to + 4, 4 },
> >> +      get_frame_register (frame, regnum + 0, second_half);
> >> +      get_frame_register (frame, regnum + 1, first_half);
> >> +
> >> +      if (!get_frame_register_bytes (next_frame, regnum + 0, 0, second_half,
> >>  				     optimizedp, unavailablep))
> >>  	return 0;
> >>
> >> -      if (!get_frame_register_bytes (next_frame, regnum + 1, 0, { to + 0, 4 },
> >> +      if (!get_frame_register_bytes (next_frame, regnum + 1, 0, first_half,
> >>  				     optimizedp, unavailablep))
> >>  	return 0;
> >>        *optimizedp = *unavailablep = 0;
> >> @@ -6257,8 +6260,10 @@ mips_read_fp_register_single (const frame_info_ptr &frame, int
> >> regno,
> >>    struct gdbarch *gdbarch = get_frame_arch (frame);
> >>    int raw_size = register_size (gdbarch, regno);
> >>    gdb_byte *raw_buffer = (gdb_byte *) alloca (raw_size);
> >> +  gdb::array_view<gdb_byte> raw_view = gdb::make_array_view (raw_buffer,
> >> +							     raw_size);
> >
> > I noticed one thing after sending the previous email on this patch.
> > For simpler code, can we use here
> >
> >   gdb::byte_vector raw_buffer (raw_size);
> >
> > and eliminate raw_view?
> 
> That's a good idea. I took this approach in order to make a minimally
> invasive patch, given that I can't test on a MIPS system.

 What needs testing?  Perhaps I can push it through (although I find MIPS 
testing unreliable in my lab recently: a lot of intermittent failures and 
I don't yet know if it's a target regression or an issue specific to 
hardware, which I had to replace with a different one not so long ago due 
to a catastrophic failure).

  Maciej