Resource acquisition is initialization: Difference between revisions

Revision as of 20:01, 12 July 2020

Revision as of 07:39, 24 July 2020

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Another typical example is interacting with files: We could have an object that represents a file that is open for writing, wherein the file is opened in the constructor and closed when execution leaves the object's scope. In both cases, RAII ensures only that the resource in question is released appropriately; care must still be taken to maintain exception safety. If the code modifying the data structure or file is not exception-safe, the mutex could be unlocked or the file closed with the data structure or file corrupted.

Ownership of dynamically allocated objects (memory allocated with <ttcode>new</ttcode> in C++) can also be controlled with RAII, such that the object is released when the RAII (stack-based) object is destroyed. For this purpose, the [[C++11]] standard library defines the [[smart pointer]] classes <code>[[Smart pointer#unique_ptr|std::unique_ptr]]</code> for single-owned objects and <code>[[Smart_pointer#shared_ptr_and_weak_ptr|std::shared_ptr]]</code> for objects with shared ownership. Similar classes are also available through <code>[[auto ptr|std::auto_ptr]]</code> in C++98, and <code>boost::shared_ptr</code> in the [[Boost (C++ libraries)|Boost libraries]].

== Clang and GCC "cleanup" extension for C ==