Remove leftover PX4_BACKTRACE

[julianoes]

Remove PX4_BACKTRACE. This follows up #12099.

[dagar]

Verify we actually get a core now?

In the tests we can save any core files + exact binary and run gdb in batch to dump the backtrace for all threads in the output.

[julianoes]

Verify we actually get a core now?

Let me try.

[julianoes]

I had to remove the segfault handler to actually get core dumps working. @bkueng does that make sense?

I triggered a segfault like this:

diff --git a/src/modules/commander/Commander.cpp b/src/modules/commander/Commander.cpp
index 15a7c199d6..f3c887c633 100644
--- a/src/modules/commander/Commander.cpp
+++ b/src/modules/commander/Commander.cpp
@@ -326,6 +326,13 @@ int commander_main(int argc, char *argv[])
                return 0;
        }
 
+       if (!strcmp(argv[1], "segfault")) {
+
+               PX4_INFO("try to read something silly: %d.", *argv[70]);
+
+               return 0;
+       }
+
        /* commands needing the app to run below */
        if (!thread_running) {
                PX4_ERR("not started");

And of course I had to enable core files:

ulimit -c unlimited

And was able to get:

gdb build/px4_sitl_default/bin/px4 /tmp/core-px4.5491.fractal.1559196660 
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Reading symbols from build/px4_sitl_default/bin/px4...
[New LWP 5491]
[New LWP 5501]
[New LWP 5495]
[New LWP 5545]
[New LWP 5497]
[New LWP 5492]
[New LWP 5761]
[New LWP 5717]
[New LWP 5848]
[New LWP 5760]
[New LWP 5742]
[New LWP 5808]
[New LWP 5802]
[New LWP 5756]
[New LWP 5798]
[New LWP 5493]
[New LWP 5752]
[New LWP 5847]
[New LWP 5783]
[New LWP 5809]
[New LWP 5794]
[New LWP 5499]
[New LWP 5765]
[New LWP 5831]
[New LWP 5558]
[New LWP 5832]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/usr/lib/libthread_db.so.1".
Core was generated by `/home/julianoes/src/Firmware/build/px4_sitl_default/bin/px4 /home/julianoes/src'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00005572a742460b in commander_main (argc=2, argv=0x7fff1f1825f0) at /home/julianoes/src/Firmware/src/modules/commander/Commander.cpp:331
331			PX4_INFO("try to read something silly: %d.", *argv[70]);
[Current thread is 1 (Thread 0x7ff4f14ae780 (LWP 5491))]
(gdb) bt
#0  0x00005572a742460b in commander_main (argc=2, argv=0x7fff1f1825f0) at /home/julianoes/src/Firmware/src/modules/commander/Commander.cpp:331
#1  0x00005572a75abfe4 in px4_daemon::Pxh::process_line (line="commander segfault", silently_fail=silently_fail@entry=false)
    at /usr/include/c++/8.3.0/bits/basic_string.h:390
#2  0x00005572a75ac651 in px4_daemon::Pxh::process_line (silently_fail=false, line="commander segfault")
    at /usr/include/c++/8.3.0/bits/basic_string.h:1031
#3  px4_daemon::Pxh::run_pxh (this=0x7fff1f182bc0) at /home/julianoes/src/Firmware/platforms/posix/src/px4_daemon/pxh.cpp:170
#4  0x00005572a73fc42a in main (argc=<optimized out>, argv=<optimized out>) at /home/julianoes/src/Firmware/platforms/posix/src/main.cpp:285
(gdb) quit

[bkueng]

Can you also remove the definition of px4_backtrace, I don't think it's used anymore?

[julianoes]

@bkueng thanks, done in e2244c6.