Re: [PATCH v2] [gdb] Fix "value is not available" with debug frame

[Kevin Buettner <kevinb@redhat.com>]

Hi Tom,

On Tue, 13 Feb 2024 18:17:18 +0100
Tom de Vries <tdevries@suse.de> wrote:

> On arm-linux, with a started hello world, running "info frame" works fine, but
> when I set debug frame to on, I run into:
> ...
> (gdb) info frame
>   ...
> [frame] frame_unwind_register_value: exit
> value is not available
> (gdb)
> ...
> 
> The problem is here in frame_unwind_register_value:
> ...
>           if (value->lazy ())
>             gdb_printf (&debug_file, " lazy");
>           else
>             {
>               int i;
>               gdb::array_view<const gdb_byte> buf = value->contents ();
> ...
> where we call value->contents () while !value->entirely_available ().
> 
> Fix this by checking value->entirely_available () and printing:
> ...
>     [frame] frame_unwind_register_value:   -> register=91 unavailable
> ...
> 
> Tested on arm-linux.

The fix looks good to me.

I'm wondering about the test case though.  Is it the case that the
failure depends on debug info from a particular compiler (or compiler
version)?  If so, would it be possible to devise a test using the
DWARF assembler which would not be dependent on compiler output that
may change over time?

Kevin