Preprocessor: Recover instead of mutating a token in ExpandBuiltinMacro

We would CreateString on arbitrary garbage instead of just skipping to
the end of the builtin macro.  Eventually, this would cause us to crash
because we would end up replacing the contents of a character token with
a numeric literal.

This fixes PR21825.

llvm-svn: 224238

1 files changed, 10 insertions, 4 deletions

diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
index d9a7f39913a..cd05d06633f 100644
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -1415,6 +1415,10 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
         if (IsScopeValid && Tok.is(tok::r_paren))
           IsValid = true;
       }
+      // Eat tokens until ')'.
+      while (Tok.isNot(tok::r_paren) && Tok.isNot(tok::eod) &&
+             Tok.isNot(tok::eof))
+        LexUnexpandedToken(Tok);
     }
 
     int Value = 0;
@@ -1441,9 +1445,10 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
       Value = HasFeature(*this, FeatureII);
     }
 
+    if (!IsValid)
+      return;
     OS << Value;
-    if (IsValid)
-      Tok.setKind(tok::numeric_constant);
+    Tok.setKind(tok::numeric_constant);
   } else if (II == Ident__has_include ||
              II == Ident__has_include_next) {
     // The argument to these two builtins should be a parenthesized
@@ -1507,9 +1512,10 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
                               WarningName.substr(2), Diags);
     } while (false);
 
+    if (!IsValid)
+      return;
     OS << (int)Value;
-    if (IsValid)
-      Tok.setKind(tok::numeric_constant);
+    Tok.setKind(tok::numeric_constant);
   } else if (II == Ident__building_module) {
     // The argument to this builtin should be an identifier. The
     // builtin evaluates to 1 when that identifier names the module we are