[PATCH] PR preprocessor/84517 allow double-underscore macros after string literals

[Jonathan Wakely <jwakely dot gcc at gmail dot com>]

Since the fix for PR c++/80955 any suffix on a string literal that
begins with an underscore is assumed to be a user-defined literal
suffix, not a macro. This assumption is invalid for a suffix beginning
with two underscores, because such names are reserved and can't be used
for UDLs anyway. Checking for exactly one underscore restores support
for macro expansion in cases like "File: "__FILE__ or "Date: "__DATE__
(which are formally ill-formed but accepted with a warning, as a
conforming extension).

gcc/testsuite:

        PR preprocessor/84517
        * g++.dg/cpp0x/udlit-macros.C: Expect a warning for ""__FILE__.

libcpp:

        PR preprocessor/84517
        * lex.c (is_macro_not_literal_suffix): New function.
        (lex_raw_string, lex_string): Use is_macro_not_literal_suffix to
        decide when to issue -Wliteral-suffix warnings.


Tested powerpc64le-linux, OK for trunk?

Attachment: patch.txt
Description: Text document