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.Dd April 9, 2008 .Dt POSIX_MEMALIGN 3 .Os .Sh NAME .Nm posix_memalign .Nd aligned memory allocation .Sh SYNOPSIS n stdlib.h .Ft int .Fo posix_memalign .Fa "void **memptr" .Fa "size_t alignment" .Fa "size_t size" .Fc .Sh DESCRIPTION The .Fn posix_memalign function allocates .Fa size bytes of memory such that the allocation's base address is an exact multiple of .Fa alignment , and returns the allocation in the value pointed to by .Fa memptr .
p The requested .Fa alignment must be a power of 2 at least as large as .Fn sizeof "void *" .
p Memory that is allocated via .Fn posix_memalign can be used as an argument in subsequent calls to .Xr realloc 3 , .Xr reallocf 3 , and .Xr free 3 . (Note however, that the allocation returned by .Xr realloc 3 or .Xr reallocf 3 is not guaranteed to preserve the original .Fa alignment ) . .Sh NOTES .Fn posix_memalign should be used judiciously as the algorithm that realizes the .Fa alignment constraint can incur significant memory overhead. .Sh RETURN VALUES The .Fn posix_memalign function returns the value 0 if successful; otherwise it returns an error value. .Sh ERRORS The .Fn posix_memalign function will fail if: l -tag -width Er t Bq Er EINVAL The .Fa alignment parameter is not a power of 2 at least as large as .Fn sizeof "void *" . t Bq Er ENOMEM Memory allocation error. .El .Sh SEE ALSO .Xr free 3 , .Xr malloc 3 , .Xr realloc 3 , .Xr reallocf 3 , .Xr valloc 3 , .Xr malloc_zone_memalign 3 .Sh STANDARDS The .Fn posix_memalign function conforms to .St -p1003.1-2001 .