Here is a simple bpftrace script:

```none
#!/usr/bin/env bpftrace

tracepoint:syscalls:sys_enter_kill
{
  $tpid = args->pid;
  printf("%d %d %d\n", $tpid, $tpid < 0, $tpid >= 0);
}

```

It traces `kill` syscalls, prints the target PID and two additional values: whether it is negative, and whether it is non-negative.

Here is the output that I get:

```none
# ./test.bt
Attaching 1 probe...
-1746 0 1
-2202 0 1
4160 0 1
4197 0 1
4197 0 1
-2202 0 1
-1746 0 1

```

Weirdly, both positive and negative pids appear to be positive for the comparison operator.

Just as a sanity, check, if I replace the assignment line with:

```none
  $tpid = -10;

```

what I get is exactly what I expect:

```none
# ./test.bt
Attaching 1 probe...
-10 1 0
-10 1 0
-10 1 0

```

What am I doing wrong?