Re: [PATCH v2] gdb/cli: fixes to newly added "list ." command

[Andrew Burgess <aburgess@redhat.com>]

Bruno Larsen via Gdb-patches <gdb-patches@sourceware.org> writes:

> After the series that added this command was pushed, Pedro mentioned
> that the news description could easily be misinterpreted, as well as
> some code and test improvements that should be made.
>
> While fixing the test, I realized that code repetition wasn't
> happening as it should, so I took care of that too.
> ---
> Changes for v2:
> * reworded documentation and help text
>
> ---
>  gdb/NEWS                        |  6 ++++--
>  gdb/cli/cli-cmds.c              | 21 ++++++++++++---------
>  gdb/doc/gdb.texinfo             |  6 +++---
>  gdb/testsuite/gdb.base/list.exp | 19 +++++++++----------
>  4 files changed, 28 insertions(+), 24 deletions(-)
>
> diff --git a/gdb/NEWS b/gdb/NEWS
> index ac5dc424d3f..93010178364 100644
> --- a/gdb/NEWS
> +++ b/gdb/NEWS
> @@ -87,8 +87,10 @@
>  * The Ada 2022 Enum_Rep and Enum_Val attributes are now supported.
>  
>  * The 'list' command now accepts '.' as an argument, which tells GDB to
> -  print the location where the inferior is stopped.  If the inferior hasn't
> -  started yet, the command will print around the main function.
> +  print the location around the default location. The default location
> +  is where the inferior is stopped in the current stack frame; if the

While reading this patch I struggled with the definition(s) of 'default
location'.  Here you talk about 'where the inferior is stopped', but I'm
not sure about that -- what about multi-threaded inferiors?  So maybe we
should say 'current thread is stopped'?

But then you also pull in the idea of the 'current stack frame'.  So I
wonder if we can actually drop reference to inferior/thread completely.
How about:

  The default location is the point of execution within the currently
  selected frame.

The phrase 'point of execution' is something I pulled from the manual --
it's used in several places.

> +  inferior didn't start yet, the command will print around the beginning
> +  of the 'main' function.

s/inferior didn't start/inferior hasn't started/ -- I think this reads
better.

>  
>  * Using the 'list' command with no arguments in a situation where the
>    command would attempt to list past the end of the file now warns the
> diff --git a/gdb/cli/cli-cmds.c b/gdb/cli/cli-cmds.c
> index 0fa24fd3df9..9b047513e02 100644
> --- a/gdb/cli/cli-cmds.c
> +++ b/gdb/cli/cli-cmds.c
> @@ -1272,10 +1272,10 @@ list_command (const char *arg, int from_tty)
>  	  print_source_lines (cursal.symtab, range, 0);
>  	}
>  
> -      /* "l ." lists the default location again.  */
> +      /* "list ." lists the default location again.  */
>        else if (arg[0] == '.')
>  	{
> -	  try
> +	  if (target_has_stack ())
>  	    {
>  	      /* Find the current line by getting the PC of the currently
>  		 selected frame, and finding the line associated to it.  */
> @@ -1283,19 +1283,19 @@ list_command (const char *arg, int from_tty)
>  	      CORE_ADDR curr_pc = get_frame_pc (frame);
>  	      cursal = find_pc_line (curr_pc, 0);
>  	    }
> -	  catch (const gdb_exception &e)
> +	  else
>  	    {
> -	      /* If there was an exception above, it means the inferior
> -		 is not running, so reset the current source location to
> -		 the default.  */
> +	      /* The inferior is not running, so reset the current source
> +		 location to the default.  */
>  	      clear_current_source_symtab_and_line ();
>  	      set_default_source_symtab_and_line ();
>  	      cursal = get_current_source_symtab_and_line ();
>  	    }
>  	  list_around_line (arg, cursal);
> -	  /* Advance argument so just pressing "enter" after using "list ."
> +	  /* Set the repeat args so just pressing "enter" after using "list ."
>  	     will print the following lines instead of the same lines again. */
> -	  arg++;
> +	  if (from_tty)
> +	    set_repeat_arguments ("");
>  	}
>  
>        return;
> @@ -2805,9 +2805,12 @@ and send its output to SHELL_COMMAND."));
>      = add_com ("list", class_files, list_command, _("\
>  List specified function or line.\n\
>  With no argument, lists ten more lines after or around previous listing.\n\
> -\"list .\" lists ten lines arond where the inferior is stopped.\n\
>  \"list +\" lists the ten lines following a previous ten-line listing.\n\
>  \"list -\" lists the ten lines before a previous ten-line listing.\n\
> +\"list .\" lists ten lines around the default location.\n\
> +The default location is around the location where the inferior is stopped\n\
> +in the current frame, or around the main function if the inferior didn't start.\n\
> +\n\
>  One argument specifies a line, and ten lines are listed around that line.\n\
>  Two arguments with comma between specify starting and ending lines to list.\n\
>  Lines can be specified in these ways:\n\
> diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
> index cd86da50f46..de44317ec6f 100644
> --- a/gdb/doc/gdb.texinfo
> +++ b/gdb/doc/gdb.texinfo
> @@ -9155,9 +9155,9 @@ Same as using with no arguments.
>  Print lines just before the lines last printed.
>  
>  @item list .
> -Print the lines surrounding the location that is where the inferior
> -is stopped.  If the inferior is not running, print around the main
> -function instead.
> +Print the default location. The default location is where the inferior

Maybe:

  Print lines surrounding the default location.  The default location is
  the point of execution within the currently selected frame.

> +is stopped in the current frame or around the beginning of the 'main'
> +function, if the inferior didn't start yet.
>  @end table
>  
>  @cindex @code{list}, how many lines to display
> diff --git a/gdb/testsuite/gdb.base/list.exp b/gdb/testsuite/gdb.base/list.exp
> index 582355996b0..520424c37c6 100644
> --- a/gdb/testsuite/gdb.base/list.exp
> +++ b/gdb/testsuite/gdb.base/list.exp
> @@ -402,18 +402,16 @@ proc test_list_invalid_args {} {
>  
>  proc test_list_current_location {} {
>      global binfile
> -    # If the first "list" command that GDB runs is "list ." GDB may be
> -    # unable to recognize that the inferior isn't running, so we should
> -    # reload the inferior to test that condition.
> +    # Restart the inferior to test "list ." before the inferior is started.

I think you mean 'Restart GDB to test ....', otherwise this sentence
makes no sense!

>      clean_restart
>      gdb_file_cmd ${binfile}
>  
> -    # Ensure that we are printing 10 lines
> +    # Ensure that we are printing 10 lines.
>      if {![set_listsize 10]} {
>  	return
>      }
>  
> -    # First guarantee that GDB prints around the main function correctly
> +    # First guarantee that GDB prints around the main function correctly.
>      gdb_test "list ." \
>  	"1.*\r\n2\[ \t\]+\r\n3\[ \t\]+int main \[)(\]+.*5\[ \t\]+int x;.*" \
>  	"list . with inferior not running"
> @@ -423,17 +421,18 @@ proc test_list_current_location {} {
>  	return
>      }
>  
> -    # Walk forward some lines
> +    # Walk forward some lines.
>      gdb_test "until 15" ".*15.*foo.*"
>  
>      # Test that the correct location is printed and that
>      # using just "list" will print the following lines.
> -    gdb_test "list ." ".*" "list current line after starting"
> -    gdb_test "list" ".*" "confirm we are printing the following lines"
> +    gdb_test "list ." "10\[ \t\]+foo \(.*\);.*19\[ \t\]+foo \(.*\);" "list current line after starting"
> +    gdb_test "list" "20\[ \t\]+foo \(.*\);.*29\[ \t\]+foo \(.*\);" "confirm we are printing the following lines"

Here, and below, you should wrap these long lines.

Within the regexp you should consider using a '^' anchor, e.g.:

    gdb_test "list ." "^10\[ \t\]+foo \(.*\);.*19\[ \t\]+foo \(.*\);" \
	"list current line after starting"

this ensures there is no output before the lines starting '10 ....'.
Obviously that suggestion applies in the other 3 locations too.

>  
>      # Test that list . will reset to current location
> -    gdb_test "list ." ".*" "list around current line again"
> -    gdb_test " " ".*" "testing repeated invocations with GDB's auto-repeat"
> +    # and that an empty line lists the following lines.
> +    gdb_test "list ." "10\[ \t\]+foo \(.*\);.*19\[ \t\]+foo \(.*\);" "list around current line again"
> +    gdb_test " " "20\[ \t\]+foo \(.*\);.*29\[ \t\]+foo \(.*\);" "testing repeated invocations with GDB's auto-repeat"
>  }
>  
>  clean_restart
> -- 
> 2.41.0

Thanks,
Andrew