posix_memalign - aligned memory allocation (ADVANCED REALTIME)
The posix_memalign() function shall allocate size bytes aligned on a boundary specified by alignment, and shall return a pointer to the allocated memory in memptr. The value of alignment shall be a power of two multiple of sizeof(void *).
Upon successful completion, the value pointed to by memptr shall be a multiple of alignment.
If the size of the space requested is 0, the behavior is implementation-defined: either a null pointer shall be returned in memptr, or the behavior shall be as if the size were some non-zero value, except that the behavior is undefined if the the value returned in memptr is used to access an object.
[CX] The free() function shall deallocate memory that has previously been allocated by posix_memalign().
Upon successful completion, posix_memalign() shall return zero; otherwise, an error number shall be returned to indicate the error and the contents of memptr shall either be left unmodified or be set to a null pointer.
If size is 0, either:
posix_memalign() shall not attempt to allocate any space, in which case either an implementation-defined error number shall be returned, or zero shall be returned with a null pointer returned in memptr, or
posix_memalign() shall attempt to allocate some space and, if the allocation succeeds, zero shall be returned and a pointer to the allocated space shall be returned in memptr. The application shall ensure that the pointer is not used to access an object.
The posix_memalign() function shall fail if:
- The value of the alignment parameter is not a power of two multiple of sizeof(void *).
- There is insufficient memory available with the requested alignment.
The following example shows how applications can obtain consistent behavior on error by setting * memptr to be a null pointer before calling posix_memalign().void *ptr = NULL; ... //do some work, which might goto error if (posix_memalign(&ptr, align, size)) goto error;
//do some more work, which might goto error ... error: free(ptr); //more cleanup;
The posix_memalign() function is part of the Advisory Information option and need not be provided on all implementations.
First released in Issue 6. Derived from IEEE Std 1003.1d-1999.
In the SYNOPSIS, the inclusion of <sys/types.h> is no longer required.
Austin Group Interpretation 1003.1-2001 #058 is applied, clarifying the value of the alignment argument in the DESCRIPTION.
Austin Group Interpretation 1003.1-2001 #152 is applied, clarifying the behavior when the size of the space requested is 0.
POSIX.1-2008, Technical Corrigendum 2, XSH/TC2-2008/0251  and XSH/TC2-2008/0252 [520,526] are applied.
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