13-272r1
From:    Bill Long
To:      J3
Date:    2013 June 24
Subject: OLD argument in ATOMIC intrinsics in TS 18508
References : N1967, 10-007r1


Discussion
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The OLD argument in the ATOMIC intrinsics is assigned the old value of
the ATOM variable just before the atomic operation takes
place. Assignment of the value to OLD is not part of the atomic
operation itself. Edits are included to clarify this.

Edits to N1967 (TS 18508 draft)
--------------------------------------

[15:9+] Add a new subclause after 7.1 General

"7.2 Atomic subroutines

An atomic subroutine is an intrinsic subroutine that performs an
action on its ATOM argument atomically. The effect of executing an
atomic subroutine is as if the subroutine were executed
instantaneously, thus not overlapping other atomic actions that might
occur asynchronously. The sequence of atomic actions within ordered
segments is specified in 2.3.5 of ISO/IEC 1539-1:2010. How sequences
of atomic actions in unordered segments interleave with each other is
processor dependent. For invocation of an atomic subroutine with an
argument OLD, the assignment of the value to OLD is not part of the
atomic action."


[16:7] In 7.3.1 change "becomes" to "is".

[16:21] In 7.3.2 change "becomes" to "is".

[16:35] In 7.3.3 change "becomes" to "is".

[17:10] In 7.3.4 change "becomes" to "is".

[17:23] In 7.3.5 change "becomes" to "is".


[28:9+] Add a new edit to 8.6 Edits to clause 13:

"{In 13.1 Classes of intrinsic procedures, append the following text
to the end of paragraph 3}

For invocation of an atomic subroutine with an argument OLD, the
assignment of the value to OLD is not part of the atomic action."