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 #90
Topic: sem_getvalue() Relevant Sections: Page 251 , clause 11.2.8 PASC
The description for sem_getvalue() states on lines 362-365: "If sem is locked, then the value returned by sem_getvalue() shall be either zero or a negative number whose absolute value represents the number of processes waiting for the semaphore at some unspecified call during the call." Is an implementation that always returns zero when sem is locked conforming? Such an implementation interprets the wording of the specification to be that the return value is EITHER zero OR a negative value ....
Yes this is conforming, the intent of the specification is to permit either implementation - either the one that always returns zero or the one that indicates the number of processes waiting on the semaphore.
Rationale for Interpretation
As noted in the proposed solution the rationale behind the current specification should allow both behaviours to be conforming. Forwarded to Interpretations group: 3 May 1998 Proposed Interpretation: 17 Jul 1998 Finalised: February 17 1999
Note to Project Editor (not part of interpretation)
The rationale should be updated to note that this is the intent.