IEEE Standards Interpretations for IEEE Std 1003.1c™-1995 IEEE Standard for Information Technology--Portable Operating System Interface (POSIX(R)) - System Application Program Interface (API) Amendment 2: Threads Extension (C Language)
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Interpretation Request #35
Topic: cancellation points Relevant Clauses: 18.1.2
In the second list ("A cancellation point may also occur"), several functions from ISO/ANSI C 1990 are omitted, specifically (at least), vprintf and vfprintf. Because printf is present, these should be also. (This is critical, since the standard specifically prohibits additional cancellation points for functions in POSIX.1 or ISO C.)
The standard is clear that vprintf and vfprintf shall not be cancellation points. Conforming implementations must conform to this. However, it it the opinion of the interpretations committee that this is an oversight on the part of the working and balloting groups and that they may be a cancellation point. This is being referred to the sponsor for consideration.
Rationale for Interpretation
Printf may be a cancellation point and it is inconsistent to not also allow vprintf and vfprintf.