Realloc
realloc is a C standard-library function that changes the size of an allocated memory block while preserving its existing contents up to the applicable size.
Modern C, Third Edition
realloc is a C library function that changes the size of an allocated storage region while preserving its existing contents up to the applicable size.
- How it is used
- Resizes dynamic arrays and output buffers while retaining their existing contents.
- How deep it goes
- Explains return values, relocation, preserved contents, pointer invalidation, and failure cleanup, without prescribing how the runtime chooses an address.
- Examples
- Uses circular-buffer growth and an optimized number-printing buffer that doubles its capacity.
- What you can do after
- Build it from scratch: resize an allocated buffer, check failure before replacing its pointer, and arrange cleanup.
Modern C
realloc is a C standard library function that changes the size of a previously allocated memory block while preserving its existing contents up to the applicable size.
- How it is used
- Uses realloc to grow or shrink dynamically allocated storage while implementing a variable-capacity circular buffer.
- How deep it goes
- Explains return-pointer relocation, prefix preservation, failure checks, and allocation accounting, while deferring broader implementation details.
- Examples
- Demonstrates realloc on a double array backing a circular buffer whose live data may occupy two wrapped chunks.
- What you can do after
- Apply it via stdlib.h to resize allocated arrays, check failure, update the owning pointer, and preserve or relocate live data safely.
Related concepts
- mallockind of · malloc is a C standard-library function that allocates a specified number of uninitialized bytes and returns a pointer to the storage or a null pointer on failure.
- freecontrasts with · free is a C standard-library function that releases dynamically allocated storage previously obtained from a compatible allocation function.
- exceptionuses · An exception is a runtime signal or object representing an abnormal condition that interrupts ordinary program flow and may be handled or propagated.
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