error: ‘mtx_buffer’ does not name a type mtx_buffer.unlock();
时间: 2024-05-11 13:17:29 浏览: 9
这个错误通常出现在使用锁的时候,因为 `mtx_buffer` 并没有被定义为类型。请确保你已经正确地声明和初始化了 `mtx_buffer` 变量,例如:
```
#include <mutex>
std::mutex mtx_buffer;
...
mtx_buffer.lock();
// some critical code
mtx_buffer.unlock();
```
如果仍然出现此错误,请检查是否包含了 `<mutex>` 头文件。
相关问题
libc++abi: terminating with uncaught exception of type std::__1::system_error: condition_variable wait failed: Invalid argument
This error occurs when a condition_variable is waiting for a notification, but the underlying condition is not valid. This can happen if the function is called with an invalid argument or if the condition was not initialized properly.
To fix this error, you need to check the arguments being passed to the condition_variable and ensure that they are valid. You may also need to initialize the condition properly before using it.
Here's an example of how to use a condition_variable:
```
#include <iostream>
#include <condition_variable>
#include <mutex>
#include <thread>
std::condition_variable cv;
std::mutex mtx;
bool ready = false;
void thread_func()
{
std::unique_lock<std::mutex> lock(mtx);
ready = true;
cv.notify_one();
}
int main()
{
std::thread t(thread_func);
std::unique_lock<std::mutex> lock(mtx);
while (!ready) {
cv.wait(lock);
}
t.join();
return 0;
}
```
In this example, we create a condition_variable named `cv`, a mutex named `mtx`, and a boolean flag called `ready`. We start a new thread that sets the `ready` flag to true and notifies the condition_variable. In the main thread, we wait for the notification by calling `cv.wait(lock)` in a loop.
Note that we need to acquire the lock before calling `cv.wait()` or `cv.notify_one()`. This ensures that the condition is modified atomically and prevents race conditions.
If you are still experiencing the error after checking your code, you may need to consult the documentation for the specific function that is throwing the exception to see if there are any known issues or limitations.
std::lock_quardstd::mutex lck(mtx):
std::lock_guard 是 C++ 标准库中的一个类模板,用于提供互斥锁的自动管理。它是基于 RAII(资源获取即初始化)原则设计的,可以确保在作用域结束时自动释放互斥锁,避免了手动管理锁的麻烦和可能的遗漏。
std::mutex 是 C++ 标准库中的一个互斥量类,用于实现线程之间的互斥访问。当多个线程需要访问共享资源时,可以使用互斥量来保证同一时间只有一个线程可以访问该资源,从而避免数据竞争和不确定的结果。
std::lock_guard<std::mutex> lck(mtx) 是使用 std::lock_guard 类模板创建一个对象 lck,并传入一个 std::mutex 对象 mtx。在创建 lck 对象时,它会自动调用 std::mutex 的 lock() 成员函数来锁定互斥量 mtx,当 lck 对象的作用域结束时,会自动调用 std::mutex 的 unlock() 成员函数来释放互斥量 mtx。
这样使用 std::lock_guard 可以确保在任何情况下都会正确地释放互斥锁,避免了因为异常或其他原因导致锁没有被释放而造成的死锁问题。