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™-1990 IEEE Standard for Information Technology--Portable Operating System Interfaces (POSIX®)

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Interpretation Request #73
Topic: ERROR numbers and additional actions Relevant Sections: 2.4

In section 2.4 [Error Numbers], lines 511-526 describe the abilities and restrictions of implementations regarding error detection. In particular, implementations "may generate errors included in this clause under circumstances other than those described in this clause, or may contain extensions or limitations that prevent some errors from occurring." Is it conforming to perform _additional_ actions upon detection of an error condition described in the Standard? For example, would it be conforming for an implementation, upon detecting a condition in write() calling for an error return and errno being set to EFBIG, to _also_ send a signal to the process? Many operating systems send a signal to a process performing a write() after having received an EFBIG for hitting the maximum file size limit. Is this conforming behavior?

Interpretation Response
Yes, the behavior is conforming, as long as it is described in the conformance documentation.

Rationale for Interpretation
The last paragraph of 3.3.1.2 Signal Generation and Delivery states: An implementation shall document any conditions not specified in this part of ISO/IEC 9945 under which the implementation generates signals. (See 1.3.1.2) This paragraph clearly states that an implementation may generate signals at times not described in this standard, as long as the conditions are described in the conformance documentation.