Re: [PATCH] dynamic printf

[Hui Zhu <teawater@gmail.com>]

Hi Stan,

This work is really cool!

I will try to make KGTP support it when it commit to trunk.


+	case gdb_agent_op_printf:
+	  {
+	    int chan, nargs, slen, i;
+	    int args[100];

Just use support 10 args, I suggest this line should be: int args[10];

+	    char *format;
+
+	    chan = aexpr->bytes[pc++];
+	    nargs = aexpr->bytes[pc++];
+	    slen = aexpr->bytes[pc++];
+	    format = (char *) &(aexpr->bytes[pc]);
+	    pc += slen;
+	    for (i = 0; i < nargs; ++i)
+	      {
+		args[i] = top;
Suggest add a check in this part, then when i bigger than 9, stop set
top tp args[i]

+		if (--sp >= 0)
+		  top = stack[sp];
+	      }
I think this part need keep, because all to value that in the stack
need be clean.


+	    /* (should re-check format before calling?) */
+	    printf (format,
+		    args[0], args[1], args[2], args[3], args[4],
+		    args[5], args[6], args[7], args[8], args[9]);
+	  }
+	  break;
+

Best,
Hui

On Wed, Feb 29, 2012 at 15:03, Stan Shebs <stanshebs@earthlink.net> wrote:
> This patch implements a "dynamic printf", which is basically a breakpoint
> with a printf;continue as its command list - but with additional features
> that make it more interesting.  First, there is an option to send the result
> to the inferior's output stream rather than to the GDB console; second,
> there is an option to do the printing in a remote agent/stub; and third, the
> agent version can continue printf'ing even after GDB detaches(!).
>
> (For those who pay attention to the competitive landscape, this is an
> Ericsson-requested GDBification of a Wind River feature.)
>
> The syntax of the command is
>
>    dprintf <location> <format>,<arg>,<arg>...
>
> where the location is as for breakpoints, while the format and args are as
> for the printf command.  So you could have something like
>
>    dprintf myfun "myfun args are %d,%d\n",arg1,arg2
>
> A setshow variable dprintf-style controls whether the printing is done by
> GDB, the inferior, or by a remote agent, and another variable
> disconnected-dprintf controls persistence upon disconnection, similarly to
> disconnected tracing.
>
> The patch itself is somewhat of a hack-n-slash through the middle of GDB,
> and there is much to critique. :-)  Partly this is because I wanted to push
> through to a genuinely useful example of target-side breakpoint commands,
> rather than doing limited-functionality "commands" in the abstract.  It also
> points up our continuing need for being able to define types of breakpoints
> by properties rather than adding enums...  I borrowed some of Luis'
> target-side conditional code, and got some inspiration from Hui Zhu's
> previous try at a printf bytecode.
>
> Anyway, without further ado, here's the patch itself.  I've skipped the
> testsuite for now, as I expect everybody will want nontrivial modifications.
> :-)
>
> Stan
>
> 2012-02-28  Stan Shebs <stan@codesourcery.com>
>
>    Add dynamic printf.
>    * breakpoint.h (enum bptype): New type bp_dprintf.
>    (struct bp_target_info): New field commands and persist.
>    (struct bp_location): New field cmd_bytecode.
>    (struct breakpoint): New field extra_string.
>    * breakpoint.c (dprintf_breakpoint_ops): New.
>    (disconnected_dprintf): New global.
>    (is_breakpoint): Add bp_dprintf.
>    (parse_format_string): New function.
>    (parse_cmd_to_aexpr): New function.
>    (build_target_command_list): New function.
>    (insert_bp_location): Call it.
>    (remove_breakpoints_pid): Skip dprintf breakpoints.
>    (bpstat_what): Add dprintf case.
>    (bptype_string): Ditto.
>    (print_one_breakpoint_location): Ditto.
>    (init_bp_location): Ditto.
>    (bkpt_print_mention): Ditto.
>    (dprintf_style_enums): New array.
>    (dprintf_style): New global.
>    (glob_extra_string): New global.
>    (init_breakpoint_sal): Handle extra string.
>    (addr_string_to_sals): Ditto.
>    (find_condition_and_thread): Add extra argument.
>    (create_breakpoint): Save away additional text at end of command.
>    (dprintf_command): New function.
>    (_initialize_breakpoint): Add new commands.
>    * common/ax.def (printf): New bytecode.
>    * ax-gdb.c (gen_printf): New function.
>    (agent_print_command): New function.
>    (_initialize_ax_gdb): Add maint agent-printf command.
>    * ax-gdb.h (gen_printf): Declare.
>    * ax-general.c (ax_print): Add printf disassembly.
>    * remote.c (remote_state) <cond_breakpoints>: New field.
>    (PACKET_BreakpointCommandss): New enum.
>    (remote_breakpoint_commands_feature): New function.
>    (remote_protocol_features): Add new BreakpointCommands entry.
>    (remote_can_run_breakpoint_commands): New function.
>    (remote_add_target_side_commands): New function.
>    (remote_insert_breakpoint): Call it.
>    (remote_insert_hw_breakpoint): Ditto.
>    (_initialize_remote): Add new packet configuration for
>    target-side breakpoint commands.
>    * target.h (struct target_ops): New field
>    to_can_run_breakpoint_commands.
>    (target_can_run_breakpoint_commands): New macro.
>    * target.c (update_current_target): Handle
>    to_can_run_breakpoint_commands.
>
>    [gdbserver]
>    * server.c (handle_query): Claim support for breakpoint commands.
>    (process_point_options): Add command case.
>    (process_serial_event): Leave running if there are printfs in
>    effect.
>    * mem-break.c (struct point_command_list): New struct.
>    (struct breakpoint): New field command_list.
>    (any_persistent_commands): New function.
>    (add_commands_to_breakpoint): New function.
>    (add_breakpoint_commands): New function.
>    (gdb_no_commands_at_breakpoint): New function.
>    (run_breakpoint_commands): New function.
>    * mem-break.h (any_persistent_commands): Declare.
>    (add_breakpoint_commands): Declare.
>    (gdb_no_commands_at_breakpoint): Declare.
>    (run_breakpoint_commands): Declare.
>    * linux-low.c (linux_wait_1): Test for and run breakpoint commands
>    locally.
>    * ax.c (gdb_eval_agent_expr): Add printf opcode.
>
>    [doc]
>    * gdb.texinfo (Dynamic Printf): New subsection.
>