This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 115e. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2024-11-11

2870. Combining absent encoding-prefixes

[Accepted as a DR at the June, 2024 meeting.]

(From submission #511.)

Subclause 5.13.5 [lex.string] paragraph 7 does not properly handle the case where both encoding-prefixes are absent:

The common encoding-prefix for a sequence of adjacent string-literals is determined pairwise as follows: If two string-literals have the same encoding-prefix , the common encoding-prefix is that encoding-prefix . If one string-literal has no encoding-prefix , the common encoding-prefix is that of the other string-literal. Any other combinations are ill-formed.

Possible resolution [SUPERSEDED]:

Change in 5.13.5 [lex.string] paragraph 7 as follows:

The common encoding-prefix for a sequence of adjacent string-literals is determined pairwise as follows: If two string-literals have the same encoding-prefix, the common encoding-prefix is that encoding-prefix. If one string-literal has no encoding-prefix, the common encoding-prefix is that of the other string-literal or is absent if the other string-literal has no encoding-prefix. Otherwise, both string-literals shall have the same encoding-prefix, and the common encoding-prefix is that encoding-prefix. Any other combinations are ill-formed.

CWG 2024-05-03

CWG preferred a holistic instead of a pairwise approach.

Proposed resolution (approved by CWG 2024-05-17):

Change in 5.13.5 [lex.string] paragraph 7 as follows:

The common encoding-prefix for a sequence of adjacent string-literals is determined pairwise as follows: If two string-literals have the same encoding-prefix , the common encoding-prefix is that encoding-prefix . If one string-literal has no encoding-prefix , the common encoding-prefix is that of the other string-literal. Any other combinations are ill-formed.

The string-literals in any sequence of adjacent string-literals shall have at most one unique encoding-prefix among them. The common encoding-prefix of the sequence is that encoding-prefix, if any.