[Preprocessor] Always discard body of #define if we failed to parse it

Summary:
Preivously we would only discard it if we failed to parse parameter lists.
If we do not consume the body, parser sees tokens inside directive. In
turn, this leads to spurious diagnostics and a crash in TokenBuffer, see
the added tests.

Reviewers: sammccall

Reviewed By: sammccall

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D65517

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@367530 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Lex/PPDirectives.cpp

@@ -33,6 +33,7 @@
 #include "clang/Lex/Token.h"
 #include "clang/Lex/VariadicMacroSupport.h"
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/STLExtras.h"
@@ -2399,6 +2400,13 @@ MacroInfo *Preprocessor::ReadOptionalMacroParameterListAndBody(
   Token Tok;
   LexUnexpandedToken(Tok);
 
+  // Ensure we consume the rest of the macro body if errors occur.
+  auto _ = llvm::make_scope_exit([&]() {
+    // The flag indicates if we are still waiting for 'eod'.
+    if (CurLexer->ParsingPreprocessorDirective)
+      DiscardUntilEndOfDirective();
+  });
+
   // Used to un-poison and then re-poison identifiers of the __VA_ARGS__ ilk
   // within their appropriate context.
   VariadicMacroScopeGuard VariadicMacroScopeGuard(*this);
@@ -2420,12 +2428,8 @@ MacroInfo *Preprocessor::ReadOptionalMacroParameterListAndBody(
   } else if (Tok.is(tok::l_paren)) {
     // This is a function-like macro definition.  Read the argument list.
     MI->setIsFunctionLike();
-    if (ReadMacroParameterList(MI, LastTok)) {
-      // Throw away the rest of the line.
-      if (CurPPLexer->ParsingPreprocessorDirective)
-        DiscardUntilEndOfDirective();
+    if (ReadMacroParameterList(MI, LastTok))
       return nullptr;
-    }
 
     // If this is a definition of an ISO C/C++ variadic function-like macro (not
     // using the GNU named varargs extension) inform our variadic scope guard

test/Preprocessor/stringize_skipped.c

@@ -0,0 +1,5 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+// Ensure we see the error from PP and do not see errors from the parser.
+
+// expected-error@+1{{'#' is not followed by a macro parameter}}
+#define INVALID() #B 10+10

unittests/Tooling/Syntax/TokensTest.cpp

@@ -298,6 +298,21 @@ file './input.cpp'
   spelled tokens:
     <empty>
   no mappings.
+)"},
+      // Should not crash on errors inside '#define' directives. Error is that
+      // stringification (#B) does not refer to a macro parameter.
+      {
+          R"cpp(
+a
+#define MACRO() A #B
+)cpp",
+          R"(expanded tokens:
+  a
+file './input.cpp'
+  spelled tokens:
+    a # define MACRO ( ) A # B
+  mappings:
+    ['#'_1, '<eof>'_9) => ['<eof>'_1, '<eof>'_1)
 )"}};
   for (auto &Test : TestCases)
     EXPECT_EQ(collectAndDump(Test.first), Test.second)