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

Andrew Burgess via Gdb-patches
2023-06-22T13:51:29Z

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