Re: [PATCH v3 3/4] gdb/cli: add '.' as an argument for 'list' command

[Andrew Burgess <aburgess@redhat.com>]

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

> Currently, after the user has used the list command once, there is no
> way to ask GDB to print the location where the inferior is stopped.

  (gdb) list *$pc

should do the job.

> This commit adds a way to do that using '.' as a new argument for the
> 'list' command.  If the inferior isn't running, the command throws an
> error.

If you start GDB with an executable, but don't start the executable, and
then just 'list', GDB does list a location.  Could 'list .' not just
replicate this behaviour instead of throwing an error?

>          The test gdb.base/list.exp was updated to test this new argument.
>
> Because this necessitated having the inferior running and the test was
> (seemingly unnecessarily) using printf in a non-essential way and it
> would make the resulting log harder to read for no benefit, it was
> replaced by a differen t statement.
>
> Reviewed-By: Eli Zaretskii <eliz@gnu.org>
> ---
>  gdb/NEWS                        |  4 ++++
>  gdb/cli/cli-cmds.c              | 26 ++++++++++++++++++++--
>  gdb/doc/gdb.texinfo             |  5 +++++
>  gdb/testsuite/gdb.base/list.exp | 38 +++++++++++++++++++++++++++++++++
>  gdb/testsuite/gdb.base/list1.c  |  2 +-
>  5 files changed, 72 insertions(+), 3 deletions(-)
>
> diff --git a/gdb/NEWS b/gdb/NEWS
> index 348e73dd15f..d3779c1e953 100644
> --- a/gdb/NEWS
> +++ b/gdb/NEWS
> @@ -85,6 +85,10 @@
>    this purpose is the last solitary line printed, if there was one,
>    else the lines around the main function.
>  
> +* 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 error out.
> +
>  * New commands
>  
>  maintenance print record-instruction [ N ]
> diff --git a/gdb/cli/cli-cmds.c b/gdb/cli/cli-cmds.c
> index 5973aebfad3..a966142eaea 100644
> --- a/gdb/cli/cli-cmds.c
> +++ b/gdb/cli/cli-cmds.c
> @@ -1232,14 +1232,14 @@ list_command (const char *arg, int from_tty)
>    const char *p;
>  
>    /* Pull in the current default source line if necessary.  */
> -  if (arg == NULL || ((arg[0] == '+' || arg[0] == '-') && arg[1] == '\0'))
> +  if (arg == NULL || ((arg[0] == '+' || arg[0] == '-' || arg[0] == '.') && arg[1] == '\0'))
>      {
>        set_default_source_symtab_and_line ();
>        symtab_and_line cursal = get_current_source_symtab_and_line ();
>  
>        /* If this is the first "list" since we've set the current
>  	 source line, center the listing around that line.  */
> -      if (get_first_line_listed () == 0)
> +      if (get_first_line_listed () == 0 && (arg == nullptr || arg[0] != '.'))
>  	{
>  	  list_around_line (arg, cursal);
>  	}
> @@ -1293,6 +1293,27 @@ list_command (const char *arg, int from_tty)
>  	  print_source_lines (cursal.symtab, range, 0);
>  	}
>  
> +      /* "l *" lists the default location again.  */

Is 'l *' here a typo?

Thanks,
Andrew

> +      else if (arg[0] == '.')
> +	{
> +	  try
> +	    {
> +	      /* Find the current line by getting the PC of the currently
> +		 selected frame, and finding the line associated to it.  */
> +	      frame_info_ptr frame = get_selected_frame (nullptr);
> +	      CORE_ADDR curr_pc = get_frame_pc (frame);
> +	      cursal = find_pc_line (curr_pc, 0);
> +	    }
> +	  catch (const gdb_exception &e)
> +	    {
> +	      /* If there was an exception above, it means the inferior
> +		 is not running, so reset the current source location to
> +		 the default.  */
> +	      error (_("Inferior is not running. No current location."));
> +	    }
> +	  list_around_line (arg, cursal);
> +	}
> +
>        return;
>      }
>  
> @@ -2800,6 +2821,7 @@ 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 before a previous ten-line listing.\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\
> diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
> index 55010f69a1c..e4e374d138c 100644
> --- a/gdb/doc/gdb.texinfo
> +++ b/gdb/doc/gdb.texinfo
> @@ -9151,8 +9151,13 @@ it prints the lines around the function @code{main}.
>  
>  @item list -
>  Print lines just before the lines last printed.
> +
> +@item list .
> +Print the lines surrounding the location that is where the inferior
> +is stopped.
>  @end table
>  
> +
>  @cindex @code{list}, how many lines to display
>  By default, @value{GDBN} prints ten source lines with any of these forms of
>  the @code{list} command.  You can change this using @code{set listsize}:
> diff --git a/gdb/testsuite/gdb.base/list.exp b/gdb/testsuite/gdb.base/list.exp
> index 35e099ebaff..f853a9b814d 100644
> --- a/gdb/testsuite/gdb.base/list.exp
> +++ b/gdb/testsuite/gdb.base/list.exp
> @@ -400,6 +400,41 @@ proc test_list_invalid_args {} {
>  	"second use of \"list +INVALID\""
>  }
>  
> +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.
> +    clean_restart
> +    gdb_file_cmd ${binfile}
> +
> +    # Ensure that we are printing 10 lines
> +    if {![set_listsize 10]} {
> +	return
> +    }
> +
> +    # First guarantee that GDB correctly identifies that the inferior
> +    # isn't running.
> +    gdb_test "list ." "Inferior is not running. No current location." \
> +	"list . with inferior not running"
> +
> +    if {![runto_main]} {
> +	warning "couldn't start inferior"
> +	return
> +    }
> +
> +    # 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"
> +
> +    # Test that list . will reset to current location
> +    gdb_test "list ." ".*" "list around current line again"
> +}
> +
>  clean_restart
>  gdb_file_cmd ${binfile}
>  
> @@ -519,4 +554,7 @@ test_list "list -" 10 2 "7-8" "5-6"
>  # the current line.
>  test_list "list -" 10 1 "7" "6"
>  
> +# Test printing the location where the inferior is stopped.
> +test_list_current_location
> +
>  remote_exec build "rm -f list0.h"
> diff --git a/gdb/testsuite/gdb.base/list1.c b/gdb/testsuite/gdb.base/list1.c
> index d694495c3fb..9297f958f46 100644
> --- a/gdb/testsuite/gdb.base/list1.c
> +++ b/gdb/testsuite/gdb.base/list1.c
> @@ -7,7 +7,7 @@ void bar (int x)
>     -
>     - */
>  {
> -    printf ("%d\n", x);
> +    x++;
>  
>      long_line ();
>  }
> -- 
> 2.40.1