gdb: make get_chars_per_line return an unsigned value

gdb: make get_chars_per_line return an unsigned value

I noticed that get_chars_per_line currently returns an 'int', but the
value it is returning, from utils.c, is an 'unsigned int'.  In some
cases this can cause weird behaviour as an unlimited width terminal
will have UINT_MAX characters per line, which will appear as negative
when returned from get_chars_per_line.

This has been the case since get_chars_per_line was added in commit:

  commit 2f2287318b33ddf855a692fcc191f6b25caf4644
  Date:   Wed Dec 16 18:18:40 2020 +0100

      [gdb/cli] Add a progress meter

Lets make get_chars_per_line return an unsigned value, and update all
the uses of this function to hold the result in an unsigned variable.

I ran into this issue when looking at print_gdb_hints (from top.c)
where a very large get_chars_per_line() value would appear negative,
and so the startup hints would be printed without a box when really
they should have been boxed.  Someone else noticed this problem while
I was building this patch, and pushed commit:

  commit 06e470d8fc0ae0e83fe0977fdf8c011998980891
  Date:   Sat Nov 29 15:48:55 2025 +0100

      gdb: handle unlimited screen width case in print_gdb_hints

This commit works around the signed / unsigned confusion entirely
within print_gdb_hints by adding a case to 'int' in one place.  The
change I present here reverts parts of 06e470d8fc0a in favour of
fixing the type of WIDTH within print_gdb_hints.

It is worth nothing that there are other bugs in print_gdb_hints
relating to how WIDTH is handled, but these are fixed in the next
commit.

By updating the return type of get_chars_per_line, I ran into some
issues in cli-out.c relating to how progress bars are handled.  The
existing code includes code like:

   if (!stream->isatty ()
       || !current_ui->input_interactive_p ()
       || chars_per_line < MIN_CHARS_PER_LINE)
     return;

The early return here triggers when progress bars should not be
printed.  Notice that when the terminal width is unlimited,
CHARS_PER_LINE will appear negative, and so the early return will
trigger.

It turns out that our testsuite depends on this; the debuginfod tests
don't expect to see a progress bar, and they don't because within the
tests we set the width to unlimited.

By "fixing" the type of CHARS_PER_LINE to 'unsigned int', an unlimited
width terminal no longer triggers the early return, and GDB starts
trying to print a progress bar in our debuginfod tests, which cause
the tests to fail.

I think the real fix is to add a new flag to allow progress bars to be
disabled, the tests can then use this.  I will add just such a flag at
the end of this series.

For now though, I propose adding a bodge.  If CHARS_PER_LINE is
UINT_MAX, then we should act as if progress bars are disabled.  The
above code now becomes:

   if (!stream->isatty ()
       || !current_ui->input_interactive_p ()
       || chars_per_line < MIN_CHARS_PER_LINE
       || chars_per_line == UINT_MAX)
     return;

This change is in cli_ui_out::clear_progress_notify.  There is a
similar change in cli_ui_out::do_progress_notify.  With these two
changes, the debuginfod tests are working again.  This bodge will be
removed by the last patch in this series.

There's no tests with this commit yet as print_gdb_hints has other
bugs which will be fixed in the next commit.  At this point I'll add
some tests.

Reviewed-By: Guinevere Larsen <guinevere@redhat.com>
Approved-By: Tom Tromey <tom@tromey.com>