DragonFly On-Line Manual Pages

Search: Section:  

POSIX_MEMALIGN(3)     DragonFly Library Functions Manual     POSIX_MEMALIGN(3)


posix_memalign, aligned_alloc -- aligned memory allocation


Standard C Library (libc, -lc)


#include <stdlib.h> int posix_memalign(void **ptr, size_t alignment, size_t size); void * aligned_alloc(size_t alignment, size_t size);


The posix_memalign() function allocates size bytes of memory such that the allocation's base address is an even multiple of alignment, and returns the allocation in the value pointed to by ptr. The requested alignment must be a power of 2 at least as large as sizeof(void *). Memory that is allocated via posix_memalign() can be used as an argument in subsequent calls to realloc(3), reallocf(3), and free(3). The aligned_alloc() is similar to posix_memalign(), but it does not have the sizeof(void *) restriction, takes just alignment and size and the allocation pointer is returned.


The posix_memalign() function is directly supported by matching the requested alignment against a zone of the slab allocator with a compatible chunking, and using the power-of-2 shortcut whenever possible. Alignments beyond those supported by the zone mechanism are still guaranteed using cute mmap(2) tricks. Our posix_memalign() is thus able to take advantage of the slab allocator to produce well-fitted results when the requests are reasonable.


The posix_memalign() function returns the value 0 if successful; otherwise it returns an error value. The aligned_alloc() returns a pointer to the allocated memory if successful; otherwise a NULL pointer is returned and errno is set.


The posix_memalign() and aligned_alloc() functions will fail if: [EINVAL] The alignment parameter is not a power of 2 at least as large as sizeof(void *). [ENOMEM] Memory allocation error.


free(3), malloc(3), realloc(3), reallocf(3), valloc(3)


The posix_memalign() function conforms to IEEE Std 1003.1-2008 (``POSIX.1''). The aligned_alloc() function conforms to ISO/IEC 9899:2011 (``ISO C11''). DragonFly 5.5 April 7, 2019 DragonFly 5.5

Search: Section: