[PATCH] tracepoint: add new trace command "printf"[0] gdb

[Hui Zhu <teawater at gmail dot com>]

Hi,

I add a new patch add new trace command "printf".
This printf is same with the simple gdb command, it can do formatted
output.  But it will happen in gdbserver part when it break by a
tracepoint.
Then the user can get the format value that he want in tracepint.  It
will be more easy and clear to handle the bug sometimes.

For example:
(gdb) trace 16
During symbol reading, DW_AT_name missing from DW_TAG_base_type.
Tracepoint 1 at 0x4004c3: file 1.c, line 16.
(gdb) tvariable $c
Trace state variable $c created, with initial value 0.
(gdb) actions
Enter actions for tracepoint 1, one per line.
End with a line saying just "end".
>printf "%d 0x%lx %d\n",$c=$c+1,$rax,argc
>end
(gdb) target remote localhost:1234
(gdb) tstart
(gdb) c

gdbserver/gdbserver  localhost:1234 ./a.out
Process ./a.out created; pid = 25804
Listening on port 1234
Remote debugging from host 127.0.0.1
1 0x7f2cb8711ec8 1
2 0x7f2cb8711ec8 2
3 0x7f2cb8711ec8 3
4 0x7f2cb8711ec8 4
5 0x7f2cb8711ec8 5
6 0x7f2cb8711ec8 6
7 0x7f2cb8711ec8 7


About the command part, I use the "printf" instead add a new commands
because the behavior of  this command is same with printf. They will
use the same function string_printf(update from ui_printf) to parse
the command arg.

To support the printf command, I add a new agent expression 0x31
printf, the format for it is:
0x31(op_printf) + arg(1/0) + format string with end by 0x0.
The arg is the number of argument of printf.  It will only be 1 (one
argument) or 0 (no argument).  I make it cannot have more than one
argument because I cannot found a good way to handle va_list that send
arguments to vprintf.
The format string with end by 0x0 is the simple format string.  It end
by 0x0 then the gdbserver can use it directly.

I didn't make the patch for doc because I am still not sure about
every part of this patch.  When this patch is OK.  I will make doc
patch for it.

Thanks,
Hui

2011-01-04  Hui Zhu  <teawater@gmail.com>

	* ax-gdb.c (gen_printf_expr_callback): New function.
	* ax-general.c (ax_memcpy): New function.
	(aop_map): Add new entry for "printf".
	(ax_print): Handle "printf".
	(ax_reqs): Ditto.
	* ax.h (agent_op): Add aop_printf.
	(ax_memcpy): Forward declare.
	* printcmd.c (printf_callback): New typedef.
	(string_printf): New function from ui_printf.
	(ui_printf): Call string_printf.
	(printf_command): Remove static.
	* tracepoint.c (printf_command, gen_printf_expr_callback,
	printf_callback, string_printf): Forward declares.
	(validate_actionline, encode_actions_1): handle printf_command.

Attachment: tp_print.txt
Description: Text document