Defect Report #407

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Submitter: Batty
Submission Date: 2011-10-14
Source: WG 14
Reference Document: N1584
Version: 1.0
Date: October 2011
Subject:

Summary

C11 seems to omit the restriction imposed in C++11 in 29.3p7 (from N3291):
For atomic operations A and B on an atomic object M, if there are memory_order_seq_cst fences X and Y such that A is sequenced before X, Y is sequenced before B, and X precedes Y in S, then B occurs later than A in the modification order of M.
Furthermore, it seems that both C11 and C++11 are missing the following two derivatives of this rule:
For atomic modifications A and B of an atomic object M, if there is a memory_order_seq_cst fence X such that A is sequenced before X, and X precedes B in S, then B occurs later than A in the modification order of M.
For atomic modifications A and B of an atomic object M, if there is a memory_order_seq_cst fence Y such that Y is sequenced before B, and A precedes Y in S, then B occurs later than A in the modification order of M.

Suggested Technical Corrigendum

See above.

Committee discussion

Oct 2011 meeting
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