This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 114b. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2024-05-06


2747. Cannot depend on an already-deleted splice

Section: 5.2  [lex.phases]     Status: DRWP     Submitter: Jim X     Date: 2021-09-14

[Accepted as a DR at the November, 2023 meeting.]

(From editorial issue 4903.)

Subclause 5.2 [lex.phases] paragraph 2 specifies:

... Each sequence of a backslash character (\) immediately followed by zero or more whitespace characters other than new-line followed by a new-line character is deleted, splicing physical source lines to form logical source lines. ... A source file that is not empty and that does not end in a new-line character, or that ends in a splice, shall be processed as if an additional new-line character were appended to the file.

This is confusing, because the first sentence deletes all splices, and then the last sentence checks for a splice that has already been deleted.

Proposed resolution (approved by CWG 2023-07-14):

Change in 5.2 [lex.phases] paragraph 2 as follows:

... Each sequence of a backslash character (\) immediately followed by zero or more whitespace characters other than new-line followed by a new-line character is deleted, splicing physical source lines to form logical source lines. ... A source file that is not empty and that (after splicing) does not end in a new-line character, or that ends in a splice, shall be processed as if an additional new-line character were appended to the file.

CWG 2023-07-14

CWG noted that a lone backslash at the end of a file remains (in the status quo and with the proposed change) and turns into an ill-formed preprocessing-token. The wording as amended seems sufficiently clear to consider issue 1698 resolved.