Re: [PATCH] gdb/debuginfod: Prevent prompt for continue during downloading.

[Aaron Merey <amerey@redhat.com>]

On Sat, Jan 28, 2023 at 10:01 AM Tom Tromey <tom@tromey.com> wrote:
> >>>>> "Aaron" == Aaron Merey via Gdb-patches <gdb-patches@sourceware.org> writes:
>
> Aaron> In some cases the prompt "--Type <RET> for more, q to quit, c to
> Aaron> continue without paging--" can appear during a large series of
> Aaron> debuginfod downloads when lines_printed exceeds lines_allowed.
>
> Aaron> This is inconvenient plus ctrl-c during this prompt could leave some
> Aaron> of gdb's internal structures in a broken state.
>
> Aaron> Fix this by adding a bool count_lines_printed to control whether
> Aaron> lines_printed is incremented when a newline is printed.  Set this
> Aaron> value to false when performing a download.
>
> There's already pagination_disabled for this.  Or you can print to a
> stream other than gdb_stdout.
>
> However, my question is why pagination is even enabled at the likely
> spots where debuginfod might be called.  I thought infrun generally
> disabled it.

I was able to get a prompt to show up with the command

  gdb  -ex 'set height 25' -ex 'start' qemu-kvm

Setting pagination_enabled to false does stop the prompt in this case,
however during testing of the on-demand downloading feature that I'm
working on [1] I saw cases where this still didn't prevent the prompt.

For example 'list main.c:50' might trigger a number of downloads where
debuginfod-related output increases lines_printed past the lines_allowed
limit.  When the source lines actually print, the prompt immediately
shows up since pagination has been re-enabled and lines_allowed was
exceeded.

Adding a count_lines_printed toggle takes care of this case too.
However I didn't realise that printing to a stream besides gdb_stdout
should avoid this.  I'll try to implement this fix using another stream.

Aaron

[1] https://sourceware.org/pipermail/gdb-patches/2022-November/193416.html