Variable-length array
A variable-length array is an array whose bound is determined at run time rather than fixed as a compile-time constant.
Modern C, Third Edition
A variable-length array is a C array whose bound is determined at run time rather than being an integer constant expression.
- How it is used
- Explains run-time-sized arrays through declaration constraints, lifetime rules, portability, and storage-exhaustion risks.
- How deep it goes
- Descends from classification to initialization, scope, lifetime, and stack behavior, but does not develop a complete implementation example.
- Examples
- Uses array-length classification, initializer-based fixed arrays, a control-flow lifetime example, and stack-exhaustion scenarios.
- What you can do after
- Evaluate VLA declarations for validity, lifetime behavior, portability, and potential stack exhaustion.
Read how Modern C, Third Edition explains variable-length array →
Modern C
A variable-length array is a C array whose length is determined at run time and whose lifetime rules differ from those of ordinary automatic objects.
- How it is used
- Distinguishes run-time-sized arrays from fixed-length arrays and establishes their declaration and lifetime restrictions.
- How deep it goes
- Defines classification, restrictions, length calculation, and lifetime, but defers broader storage details.
- Examples
- Uses initializer-sized arrays, a sizeof-based length formula, and a control-flow example contrasting VLA and non-VLA lifetime.
- What you can do after
- Apply C declaration rules to classify arrays, calculate array length, and reason about when VLA storage is valid.
Related concepts
- lifetimecontrasts with · A lifetime is the interval during which a program entity exists and remains valid or accessible under the applicable language rules.
- arraykind of · An array is an indexed, ordered collection of elements arranged in one or more dimensions, with elements accessed by position.
- initializercontrasts with · An initializer is a function, declaration, or language construct that establishes the initial value or state of an object, value, computation, or process.
- gotocontrasts with · A goto statement or instruction unconditionally transfers program execution to a labeled statement or location within the current execution unit.
- C99configured by · C99 is the ISO standard revision of the C programming language published in 1999.
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