This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 116a. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2024-12-19

1689. Syntactic nonterminal for operand of alignas

[Moved to DR at the February, 2014 meeting.]

Issue 1323 dealt with correcting the specification of the operand of alignas, which was originally given as the nonexistent term alignment-expression. It was corrected editorially to match the use of assignment-expression in 9.12.2 [dcl.align].

In 9.12.2 [dcl.align] paragraph 2, the expression is semantically constrained to be an integral constant expression. Since a constant-expression is syntactically a conditional-expression rather than an assignment-expression, it would probably make sense to change the syntactic nonterminal for the operand of alignas to be either a constant-expression or a conditional-expression.

Proposed resolution (November, 2013):

1. Change 9.12.1 [dcl.attr.grammar] paragraph 1 as follows:

alignment-specifier:
alignas ( type-id ..._opt )
alignas ( assignment-expression constant-expression ..._opt )

2. Change 9.12.2 [dcl.align] paragraph 2 as follows:

When the alignment-specifier is of the form alignas( assignment-expression constant-expression ):

• the assignment-expression constant-expression shall be an integral constant expression