This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 120c. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
2026-08-20
———
2901. Unclear semantics for near-match aliased access
Section: 7.2.1 [
] Status: CD7 Submitter: Jan Schultke Date: 2024-06-14 [Accepted as a DR at the November, 2024 meeting.]
(From submission
.)
Subclause 7.2.1 [
] paragraph 11 specifies:
... If a program attempts to access (3.1 [
]) the stored value of an object through a glvalue through which it is not type-accessible, the behavior is undefined. ...
Thus, access (read or write) to an int object using an lvalue of type unsigned int is valid. However, 7.3.2 [
] bullet 3.4 does not specify the resulting value when, for example, the object contains the value -1:
Otherwise, the object indicated by the glvalue is read (3.1 [
]), and the value contained in the object is the prvalue result. ...
Similarly, 7.6.19 [
] paragraph 2 is silent for the assignment case:
In simple assignment (=), the object referred to by the left operand is modified (3.1 [
]) by replacing its value with the result of the right operand.
Any concerns about accesses to the object representation are handled in the context of
.
Proposed resolution (approved by CWG 2024-09-13):
Change in 7.3.2 [
] bullet 3.4 as follows:
Otherwise, the object indicated by the glvalue is read (3.1 [
]), and the value contained in the object is the prvalue result. Let V be the value contained in the object. If T is an integer type, the prvalue result is the value of type T congruent (6.9.3 [
]) to V, and V otherwise. ...
Change in 7.6.1.6 [
] paragraph 1 as follows:
The value of a postfix ++ expression is the value ofobtained by applying the lvalue-to-rvalue conversion (7.3.2 [
]) to its operand. [Note 1: The value obtained is a copy of the original value. —end note] ...
Change in 7.6.19 [
] paragraph 2 as follows:
In simple assignment (=), let V be the result of the right operand; the object referred to by the left operand is modified (3.1 [
]) by replacing its value with the result of the right operandV or, if the object is of integer type, with the value congruent (6.9.3 [
]) to V.