Interpretations

Answering questions that may arise related to the meaning of portions of an IEEE standard concerning specific applications.

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 #68
Topic: XSH 2.2.2 , SEEK_* namespace Relevant Sections: XSH 2.2.2 Page: 18 Line: 668

The standard specifies that the SEEK_CUR, SEEK_END, and SEEK_SET macros shall be defined in (XBD, P223, L7843-7844, XSI shaded), (XBD, P325, L11562-11564, unshaded), and in (XBD, P412, L14546-14548, unshaded) for use in various functions including fcntl(), fseek(), and lseek().

Some implementations are adding extensions to POSIX conforming systems allowing applications to use fcntl() and the *seek() functions to skip some holes in files when copying a file or when moving a file across file system boundaries. The obvious choice for macros specifying these new capabilities start with SEEK_. At least one implementation provides the macros SEEK_DATA and SEEK_HOLE as well as the standard SEEK_CUR, SEEK_END, and SEEK_SET, but the standard doesn't currently allow implementations to make these macros visible to conforming applications using extensions unless a new feature test macro is added to make them visible. This seems like overkill.

I therefore request an interpretation asking for the standard to allow implementations to define additional macros starting with SEEK_ in , , and .

I also request that the suggested changes below be considered for inclusion in the next revision of the standard. These changes add SEEK_ to the list of Reserved Prefix strings that implementations are allowed to provide but that applications can #undef and use as they choose after the last standard header has been included.

Change:
F_, O_, S_ on P18, L668 to:
F_, O_, S_, SEEK_ with XSI shading on SEEK_.

Add: SEEK_ with the entire line having CX shading after P18, L6784.

Add: SEEK_ unshaded after P18, L699.

Interpretation Response #68
The standards clearly states the current requirements for the namespace, and conforming implementations must conform to this. However, concerns have been raised about this which are being referred to the sponsor.

Rationale for Interpretation
There was concern about extending the namespace. For this reason this interpretation recognizes that such an extension to the namespace for the current standard is nonconforming. However it was felt that reservation of the SEEK_ namespace should be considered in a future revision, and concerns are being forwarded to the sponsor.