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posix_memalign(3) [mojave man page]

POSIX_MEMALIGN(3)					   BSD Library Functions Manual 					 POSIX_MEMALIGN(3)

NAME
posix_memalign -- aligned memory allocation SYNOPSIS
#include <stdlib.h> int posix_memalign(void **memptr, size_t alignment, size_t size); DESCRIPTION
The posix_memalign() function allocates size bytes of memory such that the allocation's base address is an exact multiple of alignment, and returns the allocation in the value pointed to by memptr. 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). (Note however, that the allocation returned by realloc(3) or reallocf(3) is not guaranteed to preserve the original alignment). NOTES
posix_memalign() should be used judiciously as the algorithm that realizes the alignment constraint can incur significant memory overhead. RETURN VALUES
The posix_memalign() function returns the value 0 if successful; otherwise it returns an error value. ERRORS
The posix_memalign() function will fail if: [EINVAL] The alignment parameter is not a power of 2 at least as large as sizeof(void *). [ENOMEM] Memory allocation error. SEE ALSO
free(3), malloc(3), realloc(3), reallocf(3), valloc(3), malloc_zone_memalign(3) STANDARDS
The posix_memalign() function conforms to IEEE Std 1003.1-2001 (``POSIX.1''). BSD
April 9, 2008 BSD

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POSIX_MEMALIGN(3)					     Linux Programmer's Manual						 POSIX_MEMALIGN(3)

NAME
posix_memalign, memalign, valloc - Allocate aligned memory SYNOPSIS
#include <stdlib.h> int posix_memalign(void **memptr, size_t alignment, size_t size); void *memalign(size_t boundary, size_t size); void *valloc(size_t size); DESCRIPTION
The function posix_memalign() allocates size bytes and places the address of the allocated memory in *memptr. The address of the allocated memory will be a multiple of alignment, which must be a power of two and a multiple of sizeof(void *). The obsolete function memalign() allocates size bytes and returns a pointer to the allocated memory. The memory address will be a multiple of boundary, which must be a power of two. The obsolete function valloc() allocates size bytes and returns a pointer to the allocated memory. The memory address will be a multiple of the page size. It is equivalent to memalign(sysconf(_SC_PAGESIZE),size). For all three routines, the memory is not zeroed. RETURN VALUE
memalign() and valloc() return the pointer to the allocated memory, or NULL if the request fails. posix_memalign() returns zero on success, or one of the error values listed in the next section on failure. Note that errno is not set. ERRORS
EINVAL The alignment parameter was not a power of two, or was not a multiple of sizeof(void *). ENOMEM There was insufficient memory to fulfill the allocation request. NOTES
posix_memalign() verifies that alignment matches the requirements detailed above. memalign() may not check that the boundary parameter is correct. POSIX requires that memory obtained from posix_memalign() can be freed using free(). Some systems provide no way to reclaim memory allo- cated with memalign() or valloc() (because one can only pass to free() a pointer gotten from malloc(), while e.g. memalign() would call malloc() and then align the obtained value). GNU libc allows memory obtained from any of these three routines to be reclaimed with free(). GNU libc malloc() always returns 8-byte aligned memory addresses, so these routines are only needed if you require larger alignment values. AVAILABILITY
The functions memalign() and valloc() have been available in all Linux libc libraries. The function posix_memalign() is available since glibc 2.1.91. CONFORMING TO
The function valloc() appeared in 3.0 BSD. It is documented as being obsolete in BSD 4.3, and as legacy in SUSv2. It no longer occurs in SUSv3. The function memalign() appears in SunOS 4.1.3 but not in BSD 4.4. The function posix_memalign() comes from POSIX 1003.1d. SEE ALSO
malloc(3), free(3), getpagesize(2), brk(2) GNU
2001-10-11 POSIX_MEMALIGN(3)

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