Re: [PATCH] [gdb/cli] Add maint info screen

[Tom de Vries <tdevries@suse.de>]

On 4/27/23 22:49, John Baldwin wrote:
> On 4/17/23 7:09 AM, Tom de Vries via Gdb-patches wrote:
>> While working on PRs tui/30337 and cli/30346 I came across various 
>> notions of
>> width in gdb, as reported by gdb, readline, curses and the environment
>> variables.
>>
>> As for gdb, readline and the environment variables, the way things work
>> is:
>> - Gdb asks readline to detect screen size,
>> - readline sets the actual screen size in the environment variables
>>    COLUMNS and LINES,
>> - readline reports back a screen size to gdb, which may have one column
>>    less than the actual screen size, to deal with lack of auto-wrap.
>>    This becomes gdb's notion of screen size (in other words the point 
>> where
>>    we can expect the gdb command line to wrap),
>> - Gdb then explicitly sets readline's screen size, which readline 
>> itself may
>>    adjust to deal with lack of auto-wrap.  This becomes readlines notion
>>    of screen size (well, internally the unadjusted one, but it'll 
>> report back
>>    the adjusted one).
>>
>> Add a command "maint info screen" that prints these notions, both for 
>> width
>> and height.
>>
>> For TERM=xterm we have:
>> ...
>> $ TERM=xterm gdb -ex "maint info screen"
>> Number of characters gdb thinks are in a line is 118.
>> Number of characters readline reports are in a line is 118.
>> Number of characters curses thinks are in a line is 118.
>> Number of characters environment thinks are in a line is 118 (COLUMNS).
>> Number of lines gdb thinks are in a page is 27.
>> Number of lines readline reports are in a page is 27.
>> Number of lines curses thinks are in a page is 27.
>> Number of lines environment thinks are in a page is 27 (LINES).
>> ...
>>
>> And for TERM=ansi:
>> ...
>> $ TERM=ansi gdb -ex "maint info screen"
>> Number of characters gdb thinks are in a line is 117.
>> Number of characters readline reports are in a line is 116.
>> Number of characters curses thinks are in a line is 118.
>> Number of characters environment thinks are in a line is 118 (COLUMNS).
>> Number of lines gdb thinks are in a page is 27.
>> Number of lines readline reports are in a page is 27.
>> Number of lines curses thinks are in a page is 27.
>> Number of lines environment thinks are in a page is 27 (LINES).
>> ...
>>
>> [ The fact that we have "characters readline reports are in a line is 
>> 116" is
>> is due to gdb making readline adjust twice for the lack of auto-wrap, 
>> this is
>> PR cli/30346.
>>
>> Likewise we can detect tui/30337 by doing a resize in TUI mode and doing
>> "maint info screen":
>> ...
>> Number of characters characters curses thinks are in a line is 110.
>> Number of characters environment thinks are in a line is 111 (COLUMNS). ]
>>
>> And for TERM=ansi, with width and heigth set to 0:
>> ...
>> Number of characters gdb thinks are in a line is 4294967295 (unlimited).
>> Number of characters readline reports are in a line is 32766 
>> (unlimited - 1).
>> Number of characters curses thinks are in a line is 118.
>> Number of characters environment thinks are in a line is 118 (COLUMNS).
>> Number of lines gdb thinks are in a page is 4294967295 (unlimited).
>> Number of lines readline reports are in a page is 32767 (unlimited).
>> Number of lines curses thinks are in a page is 27.
>> Number of lines environment thinks are in a page is 27 (LINES).
>> ...
>>
>> [ Note that when doing a resize by say maximizing or de-maximizing a 
>> terminal,
>> all reported values are updated, except for curses when not in TUI mode.
>>
>> Maybe that means there's a bug.  If not, then maybe we should not print
>> the curses lines unless in TUI mode, or annotate those lines such that 
>> it's
>> clear that the values may be not up-to-date. ]
>>
>> I'd like to use this command in the regression test for PR cli/30346.
>>
>> Tested on x86_64-linux.
> 
> I was building GDB in a Linux x86-64 VM that didn't have curses-dev 
> installed and
> this change causes GDB to no longer build:

Hi, this was already reported before ( 
https://sourceware.org/bugzilla/show_bug.cgi?id=30391 ), but using your 
report I can now also reproduce it after doing "sudo zypper remove 
ncurses-devel", thanks.

- Tom