GDB tracing: No current trace frame - gdb

Question

I am trying GDB tracepoints, but I can't get any data. I start gdbserver as following:
$ gdbserver :1234 ./a.out
Process ./a.out created; pid = 13610
Listening on port 1234
I then use the following commands on my client:
$ gdb ./a.out
...
Reading symbols from /home/simark/src/test/a.out...done.
(gdb) target remote :1234
Remote debugging using :1234
Reading symbols from /lib64/ld-linux-x86-64.so.2...done.
Reading symbols from /usr/lib/debug/lib/x86_64-linux-gnu/ld-2.15.so...done.
Loaded symbols for /lib64/ld-linux-x86-64.so.2
0x00007ffff7ddb6c0 in _start () from /lib64/ld-linux-x86-64.so.2
(gdb) l
1 #include <stdio.h>
2 int foo(int a, int b) {
3 return a + b + b;
4 }
5
6 int main() {
7 int n = foo(33, 4);
8 printf("%d\n", n);
9 return 0;
10 }
(gdb) trace 3
Tracepoint 1 at 0x400526: file test.c, line 3.
(gdb) b 9
Breakpoint 2 at 0x400563: file test.c, line 9.
(gdb) actions 1
Enter actions for tracepoint 1, one per line.
End with a line saying just "end".
>collect $regs,$args
>end
(gdb) tstart
(gdb) c
Continuing.
Breakpoint 2, main () at test.c:9
9 return 0;
(gdb) tstop
(gdb) tdump
warning: No current trace frame.
(gdb)
According to the examples I saw on the web, I should have one event, because control passed over my tracepoint. Any ideas why I get no data?

Answer 1

According to the examples I saw on the web, I should have one event, because control passed over my tracepoint.
You forgot to do tfind start before doing tdump. From help tdump:
Print everything collected at the current tracepoint.
But you are not stopped at any tracepoint, you are stopped at breakpoint#2.
The tfind start selects the first trace frame in the trace buffer.