How to QT Creator not stopping at OS Signals while debugging multithreaded programms

schnedan · 4 Feb 2021, 11:50

I have this Problem since several month now...

whenever I debug a multi-threaded Program, the debugger stops at Operating system Signals (you can turn of the popup Dialog, but not the stopping itself...) which makes it impossible to debug a program!

Here a small demo program:

#include <iostream>
#include <iomanip>
#include <thread>
#include <vector>
#include <cstdint>
#include <functional>
#include <atomic>

using namespace std;

int main(){

  constexpr int32_t const max = 1000;

  bool volatile run = false;
  int32_t volatile cnt = 0;
  std::atomic_int8_t state;

  state.store(0);

  auto worker = [&cnt,&state,&run](){
    uint32_t active = 0;
    while(run && (cnt<max)){
      if(0==state){
        ++state;
        if(1==state){
          cnt = (1+cnt);
          cout << "[" <<  std::this_thread::get_id() << "] - Value: " << cnt << endl;
          ++active;
        }
        --state;
      }
      std::this_thread::sleep_for(std::chrono::microseconds(100*cnt));
    }
    cout << "[" <<  std::this_thread::get_id() << "] - Active: " << active << endl;
    return;
  };

  static constexpr int const numthreads = 10;
  std::vector<std::thread> tlst(numthreads);
  for(auto& _t:tlst){
    auto tmp = std::thread(worker);
    _t.swap(tmp);
  }

  run = true;

  while(cnt<max){}

  run = false;

  for(auto& _t:tlst){
    _t.join();
  }

  return 0;
}

plus the QT-Creator Project file:

TEMPLATE = app
CONFIG += console
CONFIG -= app_bundle
CONFIG -= qt

QMAKE_CXXFLAGS += -std=c++11 -pthread
QMAKE_CFLAGS   += -std=c99 -pthread
LIBS += -pthread

SOURCES += \
        main.cpp

If you set a Breakpoint to the line with "run = true;", you need to continue debugging (because the debugger stops at OS Signals) lets say 20-30 times like that...

prior to reaching the Breakpoint.

So if you have a cyclic process, loops, whatever, you end in a "continue debug" hell as you never know if your click ends in the next wrong stop or a line with a breakpoint.... and only 5% or less of your clicks ending up in a usefull position (a real breakpoint)

How to get normal debugging behaviour with QT Creator (like in any decent IDE)???

What it is needed: Only Stop at real breakpoints - no OS Signals! Or only Stop at OS Signals when a certain condition is meet - like only after a certain event in Code or after a certain breakpoint.

Also if a OS event is received I do not want to end in Assembler of some clib code, but in the line (after the line) of my code, where the signal was received (but again - if pthread code causes / reacts on OS Signals, I am not interested in these Signals at all! - I am Only interested in Signals which are intended for or caused by my code)

PS:
gcc (GCC) 10.2.0 - but it was the same with 9.x versions...
Linux 5.11.10-arch1-1 #1 SMP PREEMPT - but it was the same with all versions of the last lets say 12 month...

... any solution / help welcome!