How to use ThreadSanitizer to debug C++ multi-threading errors?

ThreadSanitizer (TSan) can detect multi-threading errors when C++ code is running. The steps are as follows: Compile the code: clang++ -fsanitize=thread ...Add link flag: -ltsanTSan will detect race conditions and data races, and print errors information. If there is a data race error in the code, TSan will print a message similar to "data race".

How to use ThreadSanitizer to debug C++ multi-threading errors

Introduction

ThreadSanitizer ( TSan) is a dynamic analysis tool used to detect multi-threading errors in C++ code. Unlike other debugging tools, it can detect these errors during actual runtime, not just static analysis.

Install TSan

To use TSan in your project, please follow these steps:

1. Compile your Code:

clang++ -fsanitize=thread ...

2. Add the following flags to the link command:

-ltsan

Usage

TSan will automatically Insert checking code to detect race conditions and data races. If it detects an error, it prints a message and exits the program.

Here are some common TSan error messages:

• "data race": Two threads write to a shared variable simultaneously.
• "lock-order-inversion": Two threads acquire/release locks in the wrong order.
• "deadlock": Two threads wait for the lock released by the other party.

Practical Case

Consider the following code, which has a data race error:

#include <thread>
#include <vector>

std::vector<int> v;

void thread_function(int num) {
  std::this_thread::sleep_for(std::chrono::milliseconds(100));
  v.push_back(num);
}

int main() {
  std::vector<std::thread> threads;
  for (int i = 0; i < 10; i++) {
    threads.push_back(std::thread(thread_function, i));
  }
  for (auto& t : threads) {
    t.join();
  }
}

Compile and run this code, TSan will detect to the data race error and prints a message similar to the following:

==3677061== ThreadSanitizer: data race on write to size 4 at 0x7ffc48162990 in thread T1
...
==3677061== ThreadSanitizer: data race on write to size 4 at 0x7ffc481629d0 in thread T3

Conclusion

ThreadSanitizer is a powerful tool for debugging C++ multi-threading errors. It detects these errors while actually running, speeding up the development process and ensuring code robustness.

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