US 8-021 5.5p1 [lex.pptoken] Allow skipping non-preprocessing tokens via #if #595
Description
The program is ill-formed if it has a preprocessing token matching the category of a single "other" character. [cpp.pre]p5 relaxes the directive syntax to ignore all preprocessor tokens within a skipped group. Surveying known implementations, all believe that [cpp.pre] dominates, so add a note/normative text to [lex.pptoken] to endorse the current behavior.
Proposed change:
Revise in [lex.pptoken]p1: :"If a U+0027 APOSTROPHE, a U+0022 QUOTATION MARK, or any character not in the basic character set matches the last category, the program is ill-formed unless skipping a group [cpp.cond]."