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

1104. Global-scope template arguments vs the <: digraph

[Voted into the WP at the November, 2010 meeting.]

Passing a name qualified by the global scope operator :: as a template argument can inadvertently trigger recognition of the <: digraph, causing a syntax error. This should be handled by a lexical rule similar to the special treament given to >> so that <:: would be recognized as an open angle-bracket followed by the scope-resolution operator.

Proposed resolution (August, 2010):

Insert a bullet into the list in 5.4 [lex.pptoken] paragraph 3 as follows:

If the input stream has been parsed into preprocessing tokens up to a given character:

• if the next character begins a sequence of characters that could be the prefix and initial double quote of a raw string literal, such as R", the next preprocessing token shall be a raw string literal;

• otherwise, if the next three characters are <:: and the subsequent character is neither : nor >, the < is treated as a preprocessor token by itself (and not as the first character of the alternative token <:);

• otherwise, the next preprocessing token is the longest sequence...