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In RAII, holding a resource is a class invariant, and is tied to object lifetime. Resource allocation (or acquisition) is done during object creation (specifically initialization), by the constructor, while resource deallocation (release) is done during object destruction (specifically finalization), by the destructor. In other words, resource ...
Data-flow analysis is a technique for gathering information about the possible set of values calculated at various points in a computer program.A program's control-flow graph (CFG) is used to determine those parts of a program to which a particular value assigned to a variable might propagate.
In compilers, live variable analysis (or simply liveness analysis) is a classic data-flow analysis to calculate the variables that are live at each point in the program. A variable is live at some point if it holds a value that may be needed in the future, or equivalently if its value may be read before the next time the variable is written to.
Initialization is distinct from (and preceded by) declaration, although the two can sometimes be conflated in practice. The complement of initialization is finalization, which is primarily used for objects, but not variables. Initialization is done either by statically embedding the value at compile time, or else by assignment at run time.
In C#, this analysis was formalized by Fruja, and is precise as well as sound, in the sense that all variables assigned along all control flow paths will be considered definitely assigned. [4] The Cyclone language also requires programs to pass a definite assignment analysis, but only on variables with pointer types, to ease porting of C programs.
That is, a statement such as x = expression; (i.e. the assignment of the result of an expression to a variable) clearly calls for the expression to be evaluated and the result placed in x, but what actually is in x is irrelevant until there is a need for its value via a reference to x in some later expression whose evaluation could itself be ...
a more complex model based on a shape analysis, the type of the allocation, or; one single allocation (this is called heap-insensitivity). Heap cloning: Heap- and context-sensitive analyses may further qualify each allocation site by a summary of the control flow leading to the instruction or statement performing the allocation.
Additionally, they permit lazy allocation and initialization, whereas global variables in many languages will always consume resources. [ 1 ] [ 3 ] The singleton pattern can also be used as a basis for other design patterns, such as the abstract factory , factory method , builder and prototype patterns.