C++ Concurrent Programming: How to monitor and debug concurrent programs?

Key libraries and tools for monitoring and debugging concurrent programs: Library: Thread Sanitizer (TSan) Detect data races and deadlocks std::concurrent_unordered_map Thread-safe hash map tool: GDB (GNU Debugger) Multi-thread debugging LLDB (Low Level Debugger) Advanced multi-thread debugging capabilities

C Concurrent Programming: Monitoring and Debugging Concurrent Programs

In concurrent programming, monitoring and the health of the debugger are critical. This article explains how to use libraries and tools to monitor and debug concurrent programs.

Use the library to monitor concurrent programs

1. Thread Sanitizer (TSan)

TSan is a tool used to detect data races and deadlock thread-safe libraries. It does this by inserting code at compile time and monitoring it in real time while the program is running. Using TSan is very simple, just add -fsanitize=thread to the compilation command.

// example.cpp
#include <iostream>
#include <vector>

int main() {
  std::vector<int> v;
  v.push_back(1);

  // 模拟并发访问
  std::thread t([&v] {
    v.pop_back();
  });

  t.join();
  return 0;
}

Compile this program using TSan:

g++ -fsanitize=thread example.cpp

If the program has a data race or deadlock, TSan will report an error at runtime.

2. ConcurrentHashMap

std::concurrent_unordered_map and std::concurrent_hash_map are thread-safe hash maps, Can be used to store and retrieve data in a multi-threaded environment. These mappings provide operations such as concurrent inserts, deletes, and lookups that can help avoid data races.

// example.cpp
#include <iostream>
#include <concurrent_unordered_map>

int main() {
  std::concurrent_unordered_map<int, int> data;
  data[1] = 10;

  // 模拟并发访问
  std::thread t([&data] {
    data[1]++;
  });

  t.join();

  std::cout << data[1] << std::endl;  // 输出11
  return 0;
}

Use tools to debug concurrent programs

1. GDB

GDB (GNU debugger) is a powerful Debugging tool, which supports debugging of multi-threaded programs. It allows setting breakpoints, viewing variables and tracing the call stack. To debug multi-threaded programs, you can start GDB with the -pthread option.

gdb -pthread program

2. LLDB

LLDB (low-level debugger) is a debugging tool developed by Apple. It also supports debugging of multi-threaded programs. It has many advanced features, including real-time thread monitoring, concurrency graph generation, and advanced memory debugging.

lldb program

Practical case

Suppose we have a multi-threaded server that handles concurrent requests from multiple clients. To monitor and debug this server we can:

• Use the TSan library when compiling the server code, thus detecting data races and deadlocks.
• Use std::concurrent_unordered_map in server code to store client data to avoid data races.
• Use GDB or LLDB to connect to the server process and perform real-time monitoring and debugging while it is running.

By using these technologies, we can effectively monitor and debug concurrent programs to ensure their reliability and correctness.

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