Difference between revisions of "cpp/memory/c/realloc"
From cppreference.com
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| − | Reallocates the given area of memory. It must be previously allocated by {{lc|malloc()}}, {{lc|calloc()}} or {{tt|realloc()}} and not yet freed with {{lc|free()}}, otherwise, the results are undefined. | + | Reallocates the given area of memory. It must be previously allocated by {{lc|std::malloc()}}, {{lc|std::calloc()}} or {{tt|std::realloc()}} and not yet freed with {{lc|std::free()}}, otherwise, the results are undefined. |
The reallocation is done by either: | The reallocation is done by either: | ||
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===Return value=== | ===Return value=== | ||
| − | Pointer to the beginning of newly allocated memory or {{lc|NULL}} if error has occurred. The pointer must be deallocated with {{lc|free()}}. | + | Pointer to the beginning of newly allocated memory or {{lc|NULL}} if error has occurred. The pointer must be deallocated with {{lc|std::free()}}. |
===Example=== | ===Example=== | ||
Revision as of 07:51, 15 August 2013
| Defined in header <cstdlib>
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| void* realloc( void* ptr, std::size_t new_size ); |
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Reallocates the given area of memory. It must be previously allocated by std::malloc(), std::calloc() or std::realloc() and not yet freed with std::free(), otherwise, the results are undefined.
The reallocation is done by either:
a) expanding or contracting the existing area pointed to by
ptr, if possible. The contents of the area remain unchanged up to the lesser of the new and old sizes. If the area is expanded, the contents of the new part of the array are undefined. b) allocating a new memory block of size
new_size bytes, copying memory area with size equal the lesser of the new and the old sizes, and freeing the old block.If there is not enough memory, the old memory block is not freed and null-pointer is returned.
Contents |
Notes
Because reallocation may involve bytewise copying (regardless of whether it's to expand or to contract), only the objects of Template:concept types are safe to access in the preserved part of the memory block after a call to realloc.
Parameters
| ptr | - | pointer to the memory area to be reallocated |
| new_size | - | new size of the array |
Return value
Pointer to the beginning of newly allocated memory or NULL if error has occurred. The pointer must be deallocated with std::free().
Example
| This section is incomplete Reason: no example |
See also
| C documentation for realloc
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