From c1e32fca96743194a28519bb90add1137d96f65c Mon Sep 17 00:00:00 2001
From: Alex Lorenz <arphaman@gmail.com>
Date: Wed, 11 Oct 2017 00:41:20 +0000
Subject: [PATCH] A '<' with a trigraph '#' is not a valid editor placeholder

Credit to OSS-Fuzz for discovery:
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=3137#c5

rdar://34923985

llvm-svn: 315398
---
 clang/lib/Lex/Lexer.cpp                           | 3 ++-
 clang/test/Parser/editor-placeholder-recovery.cpp | 4 ++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
index 9885ab9d3e29..0c179c0fb875 100644
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -3542,7 +3542,8 @@ LexNextToken:
     } else if (LangOpts.Digraphs && Char == '%') {     // '<%' -> '{'
       CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
       Kind = tok::l_brace;
-    } else if (Char == '#' && lexEditorPlaceholder(Result, CurPtr)) {
+    } else if (Char == '#' && /*Not a trigraph*/ SizeTmp == 1 &&
+               lexEditorPlaceholder(Result, CurPtr)) {
       return true;
     } else {
       Kind = tok::less;
diff --git a/clang/test/Parser/editor-placeholder-recovery.cpp b/clang/test/Parser/editor-placeholder-recovery.cpp
index 48c290ee9a14..d68e087d6fba 100644
--- a/clang/test/Parser/editor-placeholder-recovery.cpp
+++ b/clang/test/Parser/editor-placeholder-recovery.cpp
@@ -69,3 +69,7 @@ void Struct::method(<#Struct &x#>, noSupressionHere) { // expected-error {{unkno
   // expected-error@-2 {{editor placeholder in source file}}
 #endif
 }
+
+void handleTrigraph() {
+  <??=placeholder#> // expected-error {{expected expression}} expected-error {{expected expression}} expected-warning {{trigraph converted to '#' character}}
+}