2 files changed, 80 insertions, 1 deletions

diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index 9ef5d1514d9..aaed97c3020 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -323,6 +323,22 @@ void UnwrappedLineParser::parsePPDirective() {
   switch (FormatTok.Tok.getIdentifierInfo()->getPPKeywordID()) {
   case tok::pp_define:
     parsePPDefine();
+    return;
+  case tok::pp_if:
+    parsePPIf();
+    break;
+  case tok::pp_ifdef:
+  case tok::pp_ifndef:
+    parsePPIfdef();
+    break;
+  case tok::pp_else:
+    parsePPElse();
+    break;
+  case tok::pp_elif:
+    parsePPElIf();
+    break;
+  case tok::pp_endif:
+    parsePPEndIf();
     break;
   default:
     parsePPUnknown();
@@ -330,6 +346,48 @@ void UnwrappedLineParser::parsePPDirective() {
   }
 }
 
+void UnwrappedLineParser::pushPPConditional() {
+  if (!PPStack.empty() && PPStack.back() == PP_Unreachable)
+    PPStack.push_back(PP_Unreachable);
+  else
+    PPStack.push_back(PP_Conditional);
+}
+
+void UnwrappedLineParser::parsePPIf() {
+  nextToken();
+  if ((FormatTok.Tok.isLiteral() &&
+       StringRef(FormatTok.Tok.getLiteralData(), FormatTok.Tok.getLength()) ==
+           "0") ||
+      FormatTok.Tok.is(tok::kw_false)) {
+    PPStack.push_back(PP_Unreachable);
+  } else {
+    pushPPConditional();
+  }
+  parsePPUnknown();
+}
+
+void UnwrappedLineParser::parsePPIfdef() {
+  pushPPConditional();
+  parsePPUnknown();
+}
+
+void UnwrappedLineParser::parsePPElse() {
+  if (!PPStack.empty())
+    PPStack.pop_back();
+  pushPPConditional();
+  parsePPUnknown();
+}
+
+void UnwrappedLineParser::parsePPElIf() {
+  parsePPElse();
+}
+
+void UnwrappedLineParser::parsePPEndIf() {
+  if (!PPStack.empty())
+    PPStack.pop_back();
+  parsePPUnknown();
+}
+
 void UnwrappedLineParser::parsePPDefine() {
   nextToken();
 
@@ -1020,6 +1078,12 @@ void UnwrappedLineParser::readToken() {
       flushComments(FormatTok.NewlinesBefore > 0);
       parsePPDirective();
     }
+
+    if (!PPStack.empty() && (PPStack.back() == PP_Unreachable) &&
+        !Line->InPPDirective) {
+      continue;
+    }
+
     if (!FormatTok.Tok.is(tok::comment))
       return;
     if (FormatTok.NewlinesBefore > 0 || FormatTok.IsFirst) {
diff --git a/clang/lib/Format/UnwrappedLineParser.h b/clang/lib/Format/UnwrappedLineParser.h
index 4746951dcd7..bf3db1ea03b 100644
--- a/clang/lib/Format/UnwrappedLineParser.h
+++ b/clang/lib/Format/UnwrappedLineParser.h
@@ -17,7 +17,6 @@
 #define LLVM_CLANG_FORMAT_UNWRAPPED_LINE_PARSER_H
 
 #include "clang/Basic/IdentifierTable.h"
-#include "clang/Basic/SourceManager.h"
 #include "clang/Format/Format.h"
 #include "clang/Lex/Lexer.h"
 #include <list>
@@ -140,6 +139,11 @@ private:
   void parseBlock(bool MustBeDeclaration, unsigned AddLevels = 1);
   void parsePPDirective();
   void parsePPDefine();
+  void parsePPIf();
+  void parsePPIfdef();
+  void parsePPElIf();
+  void parsePPElse();
+  void parsePPEndIf();
   void parsePPUnknown();
   void parseStructuralElement();
   bool tryToParseBracedList();
@@ -167,6 +171,7 @@ private:
   void flushComments(bool NewlineBeforeNext);
   void pushToken(const FormatToken &Tok);
   void calculateBraceTypes();
+  void pushPPConditional();
 
   // Represents what type of block a left brace opens.
   enum LBraceState {
@@ -224,6 +229,16 @@ private:
   // position of the token in the stream (see \c AllTokens).
   SmallVector<LBraceState, 16> LBraces;
 
+  // Represents preprocessor branch type, so we can find matching
+  // #if/#else/#endif directives.
+  enum PPBranchKind {
+    PP_Conditional,  // Any #if, #ifdef, #ifndef, #elif, block outside #if 0
+    PP_Unreachable   // #if 0 or a conditional preprocessor block inside #if 0
+  };
+
+  // Keeps a stack of currently active preprocessor branching directives.
+  SmallVector<PPBranchKind, 16> PPStack;
+
   friend class ScopedLineState;
 };