Segmentation fault (when assigning boolean?)

zeyus

This is on a bela mini running v0.3.8g and I've tried both master and dev branches of the bela library (now on dev, it fixed a debugging issue where math_neon wasn't getting built in when I used make ... debug)

Latest code I'm trying is here: https://github.com/zeyus/QTM_Bela_Sonification/tree/main/src

Essentially, I'm using a 3rd party SDK which compiles and works fine, in fact I've had it running previously, and I'm struggling to find out what is causing the problem, when I run the project I get a segmentation fault, and buliding with debug and using gdb it doesn't actually seem to be very helpful in this case.

Reading symbols from /root/Bela/projects/QTM_Bela_Sonification/QTM_Bela_Sonification...done.
(gdb) run
Starting program: /root/Bela/projects/QTM_Bela_Sonification/QTM_Bela_Sonification -p32 -C4 -B2 -N0 -G0 -M0 -D0 --audio-input-gain=0 --high-performance-mode -X0 -H0,0 -H1,0 -H2,-30 -H3,-30 -H4,-30 -H5,-30 -H6,-30 -H7,-30
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/arm-linux-gnueabihf/libthread_db.so.1".
[New Thread 0xb6c8f450 (LWP 4182)]
[New Thread 0xb63ce450 (LWP 4183)]
Starting project. SR: 44100.000, ChOut: 2

Thread 1 "QTM_Bela_Sonifi" received signal SIGSEGV, Segmentation fault.
0x00049c84 in CRTProtocol::Connect (this=0x0, pServerAddr=0x9dd6f <setup::serverAddr> "192.168.6.1",
    nPort=22222, pnUDPServerPort=0xbefff81c, nMajorVersion=1, nMinorVersion=22, bBigEndian=false)
    at /root/Bela/projects/QTM_Bela_Sonification/qsdk/RTProtocol.cpp:102
102         mbBigEndian = bBigEndian;
(gdb)

gdp points to a line which assigns a bool which I'm assuming isn't the actual issue here, but as an inexperienced c++ dev I'm not used to figuring out where this is coming from. I've tried a bunch of things and haven't had success so I'm hoping to someone more experienced it's an obvious bug/fix in my code!

Calling line in render.cpp: https://github.com/zeyus/QTM_Bela_Sonification/blob/main/src/render.cpp#L188

Error line in RTProtocol.cpp: https://github.com/zeyus/QTM_Bela_Sonification/blob/main/src/qsdk/RTProtocol.cpp#L102

Link to the previously working version: (still compiles and runs)

Cheers,

zeyus

giuliomoro

zeyus 0x00049c84 in CRTProtocol::Connect (this=0x0, pServerAddr=0x9dd6f <setup::serverAddr> "192.168.6.1",
nPort=22222, pnUDPServerPort=0xbefff81c, nMajorVersion=1, nMinorVersion=22, bBigEndian=false)
at /root/Bela/projects/QTM_Bela_Sonification/qsdk/RTProtocol.cpp:102

This shows that this is 0x0. This means you called the method on an invalid pointer. Use the backtrace command to see where this got called for and then frame X to move across the call stack to see where the null pointer came in ...

zeyus

Great thanks, that explains where the error is coming from, Sunday I will be able to spend some time on this and I'm sure I can figure out where it went wrong. 🙂

zeyus

In retrospect it's obvious, but I'd copy/pasted some code (or a default param) without checking too clearly exactly what it was for, which meant I was allocating a stupid amount of memory incorrectly to a variable.

Although this did turn out to be a little more difficult to debug due to the error not being where the problem in the code was. All I had to do was change:

  // allocate char to stor version
  char *qtmVer = new char();
  // request version from QTM
  rtProtocol->GetQTMVersion(qtmVer, 5000000U);

  // allocate char to stor version
  char qtmVer[64];
  // request version from QTM
  rtProtocol->GetQTMVersion(qtmVer, sizeof(qtmVer));

But all in all, a win because I learned something, understand more, and also went through the c++ debugging process 🙂

Thanks for the help @giuliomoro