IEEE Standards Interpretation for IEEE Std 1003.1™-2001 IEEE Standard Standard for Information Technology -- Portable Operating System Interface (POSIX®)
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Interpretation Request #58
Topic: posix_memalign , alignment Relevant Sections: XSH posix_memalign Page: 885 Line: 28831
This wording in the description of posix_memalign() is ambiguous:
"The value of alignment shall be a multiple of sizeof(void *), that is also a power of two."
It can be interpreted as meaning that the value of alignment must be a power of two, but presumably what it really means is that the multiple must be a power of two, as implied by the wording of the EINVAL error:
"The value of the alignment parameter is not a power of two multiple of sizeof(void *)."
It would not make any sense to require that the value of alignment must be a power of two and must also be a multiple of sizeof(void *), as that would be impossible if sizeof(void *) is not a power of two.
on page 885 line 28831 change "shall be a multiple of sizeof(void *), that is also a power of two" to "shall be a power of two multiple of sizeof(void *)".
Interpretation Response #58
The standard is unclear on this issue, and no conformance distinction can be made between alternative implementations based on this. This is being referred to the sponsor.
Rationale for Interpretation