3 files changed, 26 insertions, 0 deletions
diff --git a/core/fxcrt/fx_extension.cpp b/core/fxcrt/fx_extension.cpp
index 62cf8a0e04..371f1b5211 100644
--- a/core/fxcrt/fx_extension.cpp
+++ b/core/fxcrt/fx_extension.cpp
@@ -6,6 +6,8 @@
 
 #include "core/fxcrt/fx_extension.h"
 
+#include "core/fxcrt/fx_fallthrough.h"
+
 #include <algorithm>
 #include <cwctype>
 
@@ -21,6 +23,7 @@ float FXSYS_wcstof(const wchar_t* pwsStr, int32_t iLength, int32_t* pUsedLen) {
   switch (pwsStr[iUsedLen]) {
     case '-':
       bNegtive = true;
+      FX_FALLTHROUGH;
     case '+':
       iUsedLen++;
       break;
diff --git a/core/fxcrt/fx_fallthrough.h b/core/fxcrt/fx_fallthrough.h
new file mode 100644
index 0000000000..5587ee2295
--- /dev/null
+++ b/core/fxcrt/fx_fallthrough.h
@@ -0,0 +1,20 @@
+// Copyright 2018 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CORE_FXCRT_FX_FALLTHROUGH_H_
+#define CORE_FXCRT_FX_FALLTHROUGH_H_
+
+// When clang suggests inserting [[clang::fallthrough]], it first checks if
+// it knows of a macro expanding to it, and if so suggests inserting the
+// macro.  This means that this macro must be used only in code internal
+// to PDFium, so that PDFium's user code doesn't end up getting suggestions
+// for FX_FALLTHROUGH instead of the user-specific fallthrough macro.
+// So do not include this header in any of PDFium's public headers.
+#if defined(__clang__)
+#define FX_FALLTHROUGH [[clang::fallthrough]]
+#else
+#define FX_FALLTHROUGH
+#endif
+
+#endif  // CORE_FXCRT_FX_FALLTHROUGH_H_
diff --git a/core/fxcrt/xml/cxml_parser.cpp b/core/fxcrt/xml/cxml_parser.cpp
index ae5fd6d0fc..64bb0ec530 100644
--- a/core/fxcrt/xml/cxml_parser.cpp
+++ b/core/fxcrt/xml/cxml_parser.cpp
@@ -14,6 +14,7 @@
 #include "core/fxcrt/cfx_utf8decoder.h"
 #include "core/fxcrt/cfx_widetextbuf.h"
 #include "core/fxcrt/fx_extension.h"
+#include "core/fxcrt/fx_fallthrough.h"
 #include "core/fxcrt/xml/cxml_content.h"
 #include "core/fxcrt/xml/cxml_element.h"
 #include "core/fxcrt/xml/cxml_parser.h"
@@ -200,6 +201,7 @@ uint32_t CXML_Parser::GetCharRef() {
             break;
           }
           iState = 1;
+          FX_FALLTHROUGH;
         case 1:
           m_dwIndex++;
           if (ch == ';') {
@@ -226,6 +228,7 @@ uint32_t CXML_Parser::GetCharRef() {
             break;
           }
           iState = 3;
+          FX_FALLTHROUGH;
         case 3:
           m_dwIndex++;
           if (ch == ';') {