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 #72
Topic: strerror return value Relevant Sections: XSH strerror Page: 1441 Line: 44901-44902

The RETURN VALUE section for strerror() says: "Upon successful completion, strerror() shall return a pointer to the generated message string. On error errno may be set, but no return value is reserved to indicate an error."

This is misleading since strerror() always returns a pointer to a message string, it doesn't only do that for successful calls. Also, there is some missing CX shading in this section and in the ERRORS section.

Change "Upon successful completion ..." to "Upon completion, whether successful or not, ..." Add CX shading to "On error errno may be set, but no return value is reserved to indicate an error."

In the ERRORS section add CX shading to line 44907, "[EINVAL] The value of errnum is not a valid error number."

Interpretation Response #72
The standards states the requirements for the return value for strerror(), and conforming implementations must conform to this. However, concerns have been raised about this which are being referred to the sponsor.

Rationale for Interpretation