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Because the implementation of shared_ptr uses reference counting, circular references are potentially a problem. A circular shared_ptr chain can be broken by changing the code so that one of the references is a weak_ptr. Multiple threads can safely simultaneously access different shared_ptr and weak_ptr objects that point to the same object. [11]
For this purpose, the C++11 standard library defines the smart pointer classes std::unique_ptr for single-owned objects and std::shared_ptr for objects with shared ownership. Similar classes are also available through std::auto_ptr in C++98, and boost::shared_ptr in the Boost libraries. Also, messages can be sent to network resources using RAII.
Thread safe, MT-safe: Use a mutex for every single resource to guarantee the thread to be free of race conditions when those resources are accessed by multiple threads simultaneously. Thread safety guarantees usually also include design steps to prevent or limit the risk of different forms of deadlocks , as well as optimizations to maximize ...
In a hazard-pointer system, each thread keeps a list of hazard pointers indicating which nodes the thread is currently accessing. (In many systems this "list" may be probably limited to only one [1] [2] or two elements.) Nodes on the hazard pointer list must not be modified or deallocated by any other thread.
Since C++11, the C++ standard library also provides smart pointers (unique_ptr, shared_ptr and weak_ptr) which can be used in some situations as a safer alternative to primitive C pointers. C++ also supports another form of reference, quite different from a pointer, called simply a reference or reference type .
Reentrancy is neither necessary nor sufficient for thread-safety in multi-threaded environments. In other words, a reentrant subroutine can be thread-safe, [1] but is not guaranteed to be [citation needed]. Conversely, thread-safe code need not be reentrant (see below for examples). Other terms used for reentrant programs include "sharable code ...
The C++11 standard made auto_ptr deprecated, replacing it with the unique_ptr class template. [3] [4] auto_ptr was fully removed in C++17. [5] For shared ownership, the shared_ptr template class can be used. shared_ptr was defined in C++11 and is also available in the Boost library for use with previous C++ versions. [6]
In multithreaded computing, the ABA problem occurs during synchronization, when a location is read twice, has the same value for both reads, and the read value being the same twice is used to conclude that nothing has happened in the interim; however, another thread can execute between the two reads and change the value, do other work, then change the value back, thus fooling the first thread ...