gdb tracepoint 使用demo

gdb对tracepoint的描述

In some applications, it is not feasible for the debugger to interrupt
the program's execution long enough for the developer to learn anything
helpful about its behavior.  If the program's correctness depends on
its real-time behavior, delays introduced by a debugger might cause the
program to change its behavior drastically, or perhaps fail, even when
the code itself is correct.  It is useful to be able to observe the
program's behavior without interrupting it.

I.demo
i.tracepoint.c

#include <stdio.h>
#include <unistd.h>

int indx;

int main(int argc, char *argv[])
{
    int res;

    indx = 0;
    while ( indx < 10000 ) {
        res = indx * 2;
        printf("%d\n", res);
        sleep(1);
        indx++;
    }

    return 0;
}

ii.Makefile

all:
	gcc -g tracepoint.c -o tracepoint

iii.command

file tracepoint
target remote 127.0.0.1:1234
trace tracepoint.c:15
actions
collect indx
end
tstart
break tracepoint.c:14
continue
continue 10
tstop
tstatus
tfind start
while($trace_frame != -1)
printf "Frame %d : indx = %d\n", $trace_frame, indx
tfind
end

II 测试
i ./tracepoint

[redhat@localhost test]$ ./tracepoint 
0
2
4

ii gdbserver

[redhat@localhost src]$ gdbserver --attach 127.0.0.1:1234 `pidof tracepoint`
Attached; pid = 18812
Listening on port 1234
Remote debugging from host 127.0.0.1

iii gdb

[redhat@localhost test]$ gdb --command=command
GNU gdb (GDB) Red Hat Enterprise Linux (7.2-50.el6)
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-redhat-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
0x00000038d8aaab80 in __nanosleep_nocancel () from /lib64/libc.so.6
Created trace state variable $trace_timestamp for target's variable 1.
Tracepoint 1 at 0x40054b: file tracepoint.c, line 15.
Breakpoint 2 at 0x400541: file tracepoint.c, line 14.

Breakpoint 2, main (argc=1, argv=0x7fff716cb1c8) at tracepoint.c:14
14	        sleep(1);

Breakpoint 2, main (argc=1, argv=0x7fff716cb1c8) at tracepoint.c:14
14	        sleep(1);
Trace stopped by a tstop command.
Collected 11 trace frames.
Trace buffer has 5242649 bytes of 5242880 bytes free (0% full).
Trace will stop if GDB disconnects.
Not looking at any trace frame.
Found trace frame 0, tracepoint 1
Frame 0 : indx = 325
Found trace frame 1, tracepoint 1
Frame 1 : indx = 326
Found trace frame 2, tracepoint 1
Frame 2 : indx = 327
Found trace frame 3, tracepoint 1
Frame 3 : indx = 328
Found trace frame 4, tracepoint 1
Frame 4 : indx = 329
Found trace frame 5, tracepoint 1
Frame 5 : indx = 330
Found trace frame 6, tracepoint 1
Frame 6 : indx = 331
Found trace frame 7, tracepoint 1
Frame 7 : indx = 332
Found trace frame 8, tracepoint 1
Frame 8 : indx = 333
Found trace frame 9, tracepoint 1
Frame 9 : indx = 334
Found trace frame 10, tracepoint 1
Frame 10 : indx = 335
No trace frame found
Missing separate debuginfos, use: debuginfo-install glibc-2.12-1.47.el6.x86_64
(gdb) 

III.locals

局部变量目前有问题，暂未找到原因

(gdb) actions
Enter actions for tracepoint 1, one per line.
End with a line saying just "end".
>collect res
DWARF operator DW_OP_call_frame_cfa cannot be translated to an agent expression
(gdb) actions
Enter actions for tracepoint 1, one per line.
End with a line saying just "end".
>collect $locals
>end
(gdb) tstart
DWARF operator DW_OP_call_frame_cfa cannot be translated to an agent expression
(gdb)