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Resource acquisition is initialization
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<p>Resource acquisition is initialization (RAII) is a <a href="/facts/Programming_idiom/jgggjC2n">programming idiom</a> used in several <a href="/facts/Object-oriented_programming/TxNMEcao">object-oriented</a>, <a href="/facts/Statically-typed_programming_language/Tz0bAMS9">statically typed</a> programming languages to describe a particular language behavior. In RAII, holding a resource is a <a href="/facts/Class_invariant/PqDFHgQy">class invariant</a>, and is tied to <a href="/facts/Object_lifetime/QgCnhNlf">object lifetime</a>. <a href="/facts/Resource_allocation_(computer)/nDcAW72z">Resource allocation</a> (or acquisition) is done during object creation (specifically initialization), by the <a href="/facts/Constructor_(object-oriented_programming)/8JNHsH5H">constructor</a>, while resource deallocation (release) is done during object destruction (specifically finalization), by the <a href="/facts/Destructor_(computer_programming)/gr4051ve">destructor</a>. In other words, resource acquisition must succeed for initialization to succeed. Thus, the resource is guaranteed to be held between when initialization finishes and finalization starts (holding the resources is a class invariant), and to be held only when the object is alive. Thus, if there are no object leaks, there are no <a href="/facts/Resource_leak/6zxNKPXA">resource leaks</a>. </p><p>RAII is associated most prominently with <a href="/facts/C%252B%252B/Et0F2qn9">C++</a>, where it originated, but also <a href="/facts/Ada_(programming_language)/Y2yHel4l">Ada</a>, <a href="/facts/Vala_(programming_language)/VnSxeM1b">Vala</a>, and <a href="/facts/Rust_(programming_language)/8JNMV19F">Rust</a>. The technique was developed for <a href="/facts/Exception_safety/Hevphbsh">exception-safe</a> <a href="/facts/Resource_management_(computing)/Nd3YPa3P">resource management</a> in C++ during 1984–1989, primarily by <a href="/facts/Bjarne_Stroustrup/Be1Yq6rn">Bjarne Stroustrup</a> and <a href="/facts/Andrew_Koenig_(programmer)/bxV8gICv">Andrew Koenig</a>, and the term itself was coined by Stroustrup. </p><p>Other names for this idiom include <i>Constructor Acquires, Destructor Releases</i> (CADRe) and one particular style of use is called <i>Scope-based Resource Management</i> (SBRM). This latter term is for the special case of <a href="/facts/Automatic_variable/S6KdHa7p">automatic variables</a>. RAII ties resources to object <i>lifetime,</i> which may not coincide with entry and exit of a scope. (Notably variables allocated on the <a href="/facts/Heap_(programming)/vthLkUpz">free store</a> have lifetimes unrelated to any given scope.) However, using RAII for automatic variables (SBRM) is the most common use case. </p>