Lex: Require that '#' be followed by a macro parameter name when preceded by '##'

After lexing a '##', we would look ahead and check to see if it was
followed by '__VA_ARGS__'.  After doing so, we would then go ahead and
lex the token.

However we would fail in the case where the '##' was followed by a '#'
followed by an identifier because we would have lexed the '#' separately
from the identifier, bypassing our parameter validation logic.

Instead, lex the tokens coming after the '##' later.

This fixes PR17804.

llvm-svn: 194059

1 files changed, 1 insertions, 6 deletions

diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
index a952b2ef1b9..9ba65a57a84 100644
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -2005,13 +2005,8 @@ void Preprocessor::HandleDefineDirective(Token &DefineTok,
             MI->getReplacementToken(NumTokens-1).is(tok::comma))
           MI->setHasCommaPasting();
 
-        // Things look ok, add the '##' and param name tokens to the macro.
+        // Things look ok, add the '##' token to the macro.
         MI->AddTokenToBody(LastTok);
-        MI->AddTokenToBody(Tok);
-        LastTok = Tok;
-
-        // Get the next token of the macro.
-        LexUnexpandedToken(Tok);
         continue;
       }