[RFA_v4 2/8] Implement frame apply [all | COUNT | -COUNT | level LEVEL... ] [FLAG]... COMMAND.

Philippe Waroquiers
2018-07-10T21:39:47Z

Implement frame apply [all | COUNT | -COUNT | level LEVEL... ] [FLAG]... COMMAND.
Also implement the command 'faas COMMAND', a shortcut for
'frame apply all -s COMMAND'.

The syntax of 'frame apply' to specify some innermost or outermost
frames is similar to 'backtrace' command, using COUNT or -COUNT.

To apply a COMMAND to a more specific set of frames, the following
new command and syntax can be used:
frame apply level LEVEL... [FLAG]... COMMAND
where LEVEL is one or more frame levels or range of frame levels.

The new command 'frame apply' allows to apply a COMMAND to a number of frames,
or to all frames, or to a set of frames.
The optional [FLAG]... arguments allow to control what output to produce
and how to handle errors raised when applying COMMAND to a frame.

Some example usages for this new command:
frame apply all info frame
Produce info frame for all frames.
frame apply all p $sp
For each frame, print the location, followed by the frame sp.
frame apply all -q p $sp
Same as before, but -q flag (q = quiet) indicates to only print
the frames sp.
frame apply all p some_local_var_somewhere
Print some_local_var_somewhere in all frames. 'frame apply'
will abort as soon as the print command fails.
frame apply all -c p some_local_var_somewhere
Same as before, but -c flag (c = continue) means to
print the error and continue applying command in case the
print command fails.
frame apply all -s p some_local_var_somewhere
Same as before, but -s flag (s = silent) means to
be silent for frames where the print command fails.
In other words, this allows to 'search' the frame in which
some_local_var_somewhere can be printed.
frame apply all -s -q p some_local_var_somewhere
Same as before, but does not print the frame info in which
the variable is found.
frame apply level 2-4 5 8-10 -s p i = i + 1
Increments i in the identified frames.

gdb/ChangeLog
2018-07-09 Philippe Waroquiers <philippe.waroquiers@skynet.be>

* stack.c: (trailing_outermost_frame): New function, mostly
extracted from backtrace_command_1.
(leading_innermost_frame): New function.
(backtrace_command_1): Update to call trailing_outermost_frame.
(frame_apply_command_count): New function.
(frame_apply_level_command): New function.
(frame_apply_all_command): New function.
(frame_apply_command): New function.
(faas_command): New function.
(frame_cmd_list): New variable.
(_initialize_stack): Update to setup the new commands 'frame apply'
and 'faas'.
---
gdb/stack.c | 308 ++++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 285 insertions(+), 23 deletions(-)

diff --git a/gdb/stack.c b/gdb/stack.c
index 13d8cf22b5..e51c689f43 100644
--- a/gdb/stack.c
+++ b/gdb/stack.c
@@ -1687,6 +1687,58 @@ info_frame_command (const char *addr_exp, int from_tty)
}
}

+/* Return the innermost frame at level LEVEL. */
+
+static struct frame_info *
+leading_innermost_frame (int level)
+{
+ struct frame_info *leading;
+
+ leading = get_current_frame ();
+
+ gdb_assert (level >= 0);
+
+ while (leading != nullptr && level)
+ {
+ QUIT;
+ leading = get_prev_frame (leading);
+ level--;
+ }
+
+ return leading;
+}
+
+/* Return the starting frame needed to handle COUNT outermost frames. */
+
+static struct frame_info *
+trailing_outermost_frame (int count)
+{
+ struct frame_info *current;
+ struct frame_info *trailing;
+
+ trailing = get_current_frame ();
+
+ gdb_assert (count > 0);
+
+ current = trailing;
+ while (current != nullptr && count--)
+ {
+ QUIT;
+ current = get_prev_frame (current);
+ }
+
+ /* Will stop when CURRENT reaches the top of the stack.
+ TRAILING will be COUNT below it. */
+ while (current != nullptr)
+ {
+ QUIT;
+ trailing = get_prev_frame (trailing);
+ current = get_prev_frame (current);
+ }
+
+ return trailing;
+}
+
/* Print briefly all stack frames or just the innermost COUNT_EXP
frames. */

@@ -1751,32 +1803,14 @@ backtrace_command_1 (const char *count_exp, frame_filter_flags flags,
variable TRAILING to the frame from which we should start
printing. Second, it must set the variable count to the number
of frames which we should print, or -1 if all of them. */
- trailing = get_current_frame ();

if (count_exp != NULL && count < 0)
{
- struct frame_info *current;
-
- count = -count;
-
- current = trailing;
- while (current && count--)
- {
- QUIT;
- current = get_prev_frame (current);
- }
-
- /* Will stop when CURRENT reaches the top of the stack.
- TRAILING will be COUNT below it. */
- while (current)
- {
- QUIT;
- trailing = get_prev_frame (trailing);
- current = get_prev_frame (current);
- }
-
+ trailing = trailing_outermost_frame (-count);
count = -1;
}
+ else
+ trailing = get_current_frame ();

for (fi = trailing; fi && count--; fi = get_prev_frame (fi))
{
@@ -2494,9 +2528,198 @@ func_command (const char *arg, int from_tty)
}
}

+/* Apply a GDB command to all stack frames, or a set of identified frames,
+ or innermost COUNT frames.
+ With a negative COUNT, apply command on outermost -COUNT frames.
+
+ frame apply 3 info frame Apply 'info frame' to frames 0, 1, 2
+ frame apply -3 info frame Apply 'info frame' to outermost 3 frames.
+ frame apply all x/i $pc Apply 'x/i $pc' cmd to all frames.
+ frame apply all -s p local_var_no_idea_in_which_frame
+ If a frame has a local variable called
+ local_var_no_idea_in_which_frame, print frame
+ and value of local_var_no_idea_in_which_frame.
+ frame apply all -s -q p local_var_no_idea_in_which_frame
+ Same as before, but only print the variable value.
+ frame apply level 2-5 0 4-7 -s p i = i + 1
+ Adds 1 to the variable i in the specified frames.
+ Note that i will be incremented twice in
+ frames 4 and 5. */
+
+/* Apply a GDB command to COUNT stack frames, starting at TRAILING.
+ CMD starts with 0 or more qcs flags followed by the GDB command to apply.
+ COUNT -1 means all frames starting at TRAILING. WHICH_COMMAND is used
+ for error messages. */
+
+static void
+frame_apply_command_count (const char *which_command,
+ const char *cmd, int from_tty,
+ struct frame_info *trailing, int count)
+{
+ qcs_flags flags;
+ struct frame_info *fi;
+
+ while (cmd != NULL && parse_flags_qcs (which_command, &cmd, &flags))
+ ;
+
+ if (cmd == NULL || *cmd == '\0')
+ error (_("Please specify a command to apply on the selected frames"));
+
+ /* The below will restore the current inferior/thread/frame.
+ Usually, only the frame is effectively to be restored.
+ But in case CMD switches of inferior/thread, better restore
+ these also. */
+ scoped_restore_current_thread restore_thread;
+
+ for (fi = trailing; fi && count--; fi = get_prev_frame (fi))
+ {
+ QUIT;
+
+ select_frame (fi);
+ TRY
+ {
+ std::string cmd_result;
+ {
+ /* In case CMD switches of inferior/thread/frame, the below
+ restores the inferior/thread/frame. FI can then be
+ set to the selected frame. */
+ scoped_restore_current_thread restore_fi_current_frame;
+
+ cmd_result = execute_command_to_string (cmd, from_tty);
+ }
+ fi = get_selected_frame (_("frame apply "
+ "unable to get selected frame."));
+ if (!flags.silent || cmd_result.length () > 0)
+ {
+ if (!flags.quiet)
+ print_stack_frame (fi, 1, LOCATION, 0);
+ printf_filtered ("%s", cmd_result.c_str ());
+ }
+ }
+ CATCH (ex, RETURN_MASK_ERROR)
+ {
+ fi = get_selected_frame (_("frame apply "
+ "unable to get selected frame."));
+ if (!flags.silent)
+ {
+ if (!flags.quiet)
+ print_stack_frame (fi, 1, LOCATION, 0);
+ if (flags.cont)
+ printf_filtered ("%s\n", ex.message);
+ else
+ throw_exception (ex);
+ }
+ }
+ END_CATCH;
+ }
+}
+
+/* Implementation of the "frame apply level" command. */
+
+static void
+frame_apply_level_command (const char *cmd, int from_tty)
+{
+ if (!target_has_stack)
+ error (_("No stack."));
+
+ bool level_found = false;
+ const char *levels_str = cmd;
+ number_or_range_parser levels (levels_str);
+
+ /* Skip the LEVEL list to find the flags and command args. */
+ while (!levels.finished ())
+ {
+ const int level_beg = levels.get_number ();
+
+ level_found = true;
+ if (levels.in_range ())
+ levels.skip_range ();
+ }
+
+ if (!level_found)
+ error (_("Missing or invalid LEVEL... argument"));
+
+ cmd = levels.cur_tok ();
+
+ /* Redo the LEVELS parsing, but applying COMMAND. */
+ levels.init (levels_str);
+ while (!levels.finished ())
+ {
+ const int level_beg = levels.get_number ();
+ int n_frames;
+
+ if (levels.in_range ())
+ {
+ n_frames = levels.end_value () - level_beg + 1;
+ levels.skip_range ();
+ }
+ else
+ n_frames = 1;
+
+ frame_apply_command_count ("frame apply level", cmd, from_tty,
+ leading_innermost_frame (level_beg), n_frames);
+ }
+}
+
+/* Implementation of the "frame apply all" command. */
+
+static void
+frame_apply_all_command (const char *cmd, int from_tty)
+{
+ if (!target_has_stack)
+ error (_("No stack."));
+
+ frame_apply_command_count ("frame apply all", cmd, from_tty,
+ get_current_frame (), INT_MAX);
+}
+
+/* Implementation of the "frame apply" command. */
+
+static void
+frame_apply_command (const char* cmd, int from_tty)
+{
+ int count;
+ struct frame_info *trailing;
+
+ if (!target_has_stack)
+ error (_("No stack."));
+
+ if (cmd == NULL)
+ error (_("Missing COUNT argument."));
+ count = get_number_trailer (&cmd, 0);
+ if (count == 0)
+ error (_("Invalid COUNT argument."));
+
+ if (count < 0)
+ {
+ trailing = trailing_outermost_frame (-count);
+ count = -1;
+ }
+ else
+ trailing = get_current_frame ();
+
+ frame_apply_command_count ("frame apply", cmd, from_tty,
+ trailing, count);
+}
+
+/* Implementation of the "faas" command. */
+
+static void
+faas_command (const char *cmd, int from_tty)
+{
+ std::string expanded = std::string ("frame apply all -s ") + cmd;
+ execute_command (expanded.c_str (), from_tty);
+}
+
+
+/* Commands with a prefix of `frame'. */
+struct cmd_list_element *frame_cmd_list = NULL;
+
void
_initialize_stack (void)
{
+ static struct cmd_list_element *frame_apply_list = NULL;
+
add_com ("return", class_stack, return_command, _("\
Make selected stack frame return to its caller.\n\
Control remains in the debugger, but when you continue\n\
@@ -2519,14 +2742,53 @@ An argument says how many frames down to go."));
Same as the `down' command, but does not print anything.\n\
This is useful in command scripts."));

- add_com ("frame", class_stack, frame_command, _("\
+ add_prefix_cmd ("frame", class_stack, frame_command, _("\
Select and print a stack frame.\nWith no argument, \
print the selected stack frame. (See also \"info frame\").\n\
An argument specifies the frame to select.\n\
-It can be a stack frame number or the address of the frame."));
+It can be a stack frame number or the address of the frame."),
+ &frame_cmd_list, "frame ", 1, &cmdlist);

add_com_alias ("f", "frame", class_stack, 1);

+#define FRAME_APPLY_FLAGS_HELP "\
+Prints the frame location information followed by COMMAND output.\n\
+FLAG arguments are -q (quiet), -c (continue), -s (silent).\n\
+Flag -q disables printing the frame location information.\n\
+By default, if a COMMAND raises an error, frame apply is aborted.\n\
+Flag -c indicates to print the error and continue.\n\
+Flag -s indicates to silently ignore a COMMAND that raises an error\n\
+or produces no output."
+
+ add_prefix_cmd ("apply", class_stack, frame_apply_command,
+ _("Apply a command to a number of frames.\n\
+Usage: frame apply COUNT [FLAG]... COMMAND\n\
+With a negative COUNT argument, applies the command on outermost -COUNT frames.\n"
+FRAME_APPLY_FLAGS_HELP),
+ &frame_apply_list, "frame apply ", 1, &frame_cmd_list);
+
+ add_cmd ("all", class_stack, frame_apply_all_command,
+ _("\
+Apply a command to all frames.\n\
+\n\
+Usage: frame apply all [FLAG]... COMMAND\n"
+FRAME_APPLY_FLAGS_HELP),
+ &frame_apply_list);
+
+ add_cmd ("level", class_stack, frame_apply_level_command,
+ _("\
+Apply a command to a list of frames.\n\
+\n\
+Usage: frame apply level LEVEL... [FLAG]... COMMAND\n\
+ID is a space-separated list of LEVELs of frames to apply COMMAND on.\n"
+FRAME_APPLY_FLAGS_HELP),
+ &frame_apply_list);
+
+ add_com ("faas", class_stack, faas_command, _("\
+Apply a command to all frames (ignoring errors and empty output).\n\
+Usage: faas COMMAND\n\
+shortcut for 'frame apply all -s COMMAND'"));
+
add_com_suppress_notification ("select-frame", class_stack, select_frame_command, _("\
Select a stack frame without printing anything.\n\
An argument specifies the frame to select.\n\
--
2.18.0