情况一：多线程代码操作的是同一个shared_ptr的对象 比如std::thread的回调函数，是一个lambda表达式，...
This is fine, in fact you can do this in all threads as much as you want. And then when local_instance is destructed (by going out of scope), it is also thread-safe. Somebody can be accessing global_instance and it won't make a difference. The snippet you pulled from msdn basically...
#include<iostream>#include<memory>#include<thread>#include<chrono>#include<mutex>#include<vector>std::shared_ptr<int>global_instance=std::make_shared<int>(0);std::mutexm;constexprintmax_loop=10000;voidthread_fcn(){// thread-safe reference countingfor(inti=0;i<max_loop;i++){std::shared_...
【Different shared_ptr instances can be "written to"(accessed using mutable operations such as operator= or reset) simultaneouslyby multiple threads (even when these instances are copies, and share the samereference count underneath.) 】 3. 任何其他并发访问的结果都是无定义的。【Any other simultane...
// thread Ashared_ptr<int>p2(p);// reads p// thread Bshared_ptr<int>p3(p);// OK, multiple reads are safe Code Example 5. Writing differentshared_ptrinstances from two threads 引用计数改变 原子操作 安全 代码语言:javascript 复制
std::shared_ptr<Base> lp= p;// thread-safe, even though the// shared use_count is incremented{staticstd::mutexio_mutex;std::lock_guard<std::mutex> lk(io_mutex);std::cout<<"local pointer in a thread:\n"<<" lp.get() = "<< lp.get()<<", lp.use_count() = "<< lp.use_...
However, std::weak_ptr has a neat trick up its sleeve -- because it has access to the reference count for an object, it can determine if it is pointing to a valid object or not! If the reference count is non-zero, the resource is still valid. If the reference count is zero, ...
s byconst&. It will not likely cause trouble (except in the unlikely case that the referencedshared_ptris deleted during the function call, as detailed by Earwicker) and it will likely be faster if you pass a lot of these around. Remember; the defaultboost::shared_ptris thread safe, so...
Note that the control block of ashared_ptris thread-safe: different non-atomicstd::shared_ptrobjects can be accessed using mutable operations, such asoperator=orreset, simultaneously by multiple threads, even when these instances are copies, and share the same control block internally. ...
这里没有std::unique_ptr提供的一些东西，特别是别名构造函数(因此您可以拥有所引用的对象的包含对象)和...