DragonFly On-Line Manual Pages
POSIX_MEMALIGN(3) DragonFly Library Functions Manual POSIX_MEMALIGN(3)
posix_memalign, aligned_alloc -- aligned memory allocation
Standard C Library (libc, -lc)
posix_memalign(void **ptr, size_t alignment, size_t size);
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
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() function is the same as posix_memalign(), but it
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 compati-
ble chunking, and using the power-of-2 shortcut whenever possible.
Alignments beyond those supported by the zone mechanism are still guaran-
teed 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; other-
wise 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 5.3 August 9, 2012 DragonFly 5.3