stl 里面的 map 是否自带锁的?

[Sandrer]

今天调试程序的时候, 崩在图片上的位置了
发现 map 里面自带锁的?

vs2010 + win7

[Sandrer]

引用 1 楼 zhao4zhong1 的回复:

否

那为什么程序会崩在加锁的地方??? 崩溃的地方是从 std::map::begin() 函数一直深入进去的

[赵4老师]

崩溃的时候在弹出的对话框按相应按钮进入调试，按Alt+7键查看Call Stack即“调用堆栈”里面从上到下列出的对应从里层到外层的函数调用历史。双击某一行可将光标定位到此次调用的源代码或汇编指令处，看不懂时双击下一行，直到能看懂为止。 《Windows核心编程》

[xskxzr]

加不加锁，怎么加锁是实现问题。 标准规定容器的线程安全如下：

引用

1. All container functions can be called concurrently by different threads on different containers. More generally, the C++ standard library functions do not read objects accessible by other threads unless those objects are directly or indirectly accessible via the function arguments, including the this pointer. 2. All const member functions can be called concurrently by different threads on the same container. In addition, the member functions begin(), end(), rbegin(), rend(), front(), back(), data(), find(), lower_bound(), upper_bound(), equal_range(), at(), and, except in associative containers, operator[], behave as const for the purposes of thread safety (that is, they can also be called concurrently by different threads on the same container). More generally, the C++ standard library functions do not modify objects unless those objects are accessible, directly or indirectly, via the function's non-const arguments, including the this pointer. 3. Different elements in the same container can be modified concurrently by different threads, except for the elements of std::vector<bool> (for example, a vector of std::future objects can be receiving values from multiple threads). 4. Iterator operations (e.g. incrementing an iterator) read, but do not modify the underlying container, and may be executed concurrently with operations on other iterators on the same container, with the const member functions, or reads from the elements. Container operations that invalidate any iterators modify the container and cannot be executed concurrently with any operations on existing iterators even if those iterators are not invalidated. 5. Elements of the same container can be modified concurrently with those member functions that are not specified to access these elements. More generally, the C++ standard library functions do not read objects indirectly accessible through their arguments (including other elements of a container) except when required by its specification. 6. In any case, container operations (as well as algorithms, or any other C++ standard library functions) may be parallelized internally as long as this does not change the user-visible results (e.g. std::transform may be parallelized, but not std::for_each which is specified to visit each element of a sequence in order)

——http://en.cppreference.com/w/cpp/container

[走好每一步]

没加锁的，自己加一下，很简单的。

[FoolCarpe]

STL标准中未提出map为线程安全 std::map崩溃可能是迭代器访问失效？

[跑马溜溜的山上]

应该没有加锁！我以前两个线程同时push_back一个list，结果挂了。 VC2010。 如果默认加锁的话，可能会影响到单线程操作的性能。

[paschen]

map标准是没有加锁的，需要进行加锁，代码里有个lock不代表是为了同步访问而去加锁，可能是为了其他需要，也可能是debug下的异常检测，具体取决于代码实现

[赵4老师]

否