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This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 119a. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2025-12-20

438. Possible flaw in wording for multiple accesses to object between sequence points

Lisa Lippincott mentioned this case to me:

  A[0] = 0;  A[A[0]] = 1;

This seems to use the old value of A[0] other than to calculate the newvalue, which is said to be undefined, but it also seems reasonable, sincethe old value is used in order to select the object to modify, so there'sno ordering ambiguity.

Steve Adamczyk: the ordering rule referred to is inClause 7 [expr] paragraph 4.

Notes from the March 2004 meeting:

Clark Nelson mentions that the C committee may have done something onthis.

Note (July, 2009):

This issue was resolved by the adoption of the “sequencedbefore” wording.