1 files changed, 33 insertions, 5 deletions

diff --git a/lib/Lex/PPDirectives.cpp b/lib/Lex/PPDirectives.cpp
index 89c2ebd00a683..8c79e50176e18 100644
--- a/lib/Lex/PPDirectives.cpp
+++ b/lib/Lex/PPDirectives.cpp
@@ -538,7 +538,7 @@ void Preprocessor::SkipExcludedConditionalBlock(SourceLocation IfTokenLoc,
           assert(CurPPLexer->LexingRawMode && "We have to be skipping here!");
           CurPPLexer->LexingRawMode = false;
           IdentifierInfo *IfNDefMacro = nullptr;
-          const bool CondValue = EvaluateDirectiveExpression(IfNDefMacro);
+          const bool CondValue = EvaluateDirectiveExpression(IfNDefMacro).Conditional;
           CurPPLexer->LexingRawMode = true;
           if (Callbacks) {
             const SourceLocation CondEnd = CurPPLexer->getSourceLocation();
@@ -635,7 +635,7 @@ void Preprocessor::PTHSkipExcludedConditionalBlock() {
     // Evaluate the condition of the #elif.
     IdentifierInfo *IfNDefMacro = nullptr;
     CurPTHLexer->ParsingPreprocessorDirective = true;
-    bool ShouldEnter = EvaluateDirectiveExpression(IfNDefMacro);
+    bool ShouldEnter = EvaluateDirectiveExpression(IfNDefMacro).Conditional;
     CurPTHLexer->ParsingPreprocessorDirective = false;
 
     // If this condition is true, enter it!
@@ -2654,7 +2654,13 @@ void Preprocessor::HandleIfdefDirective(Token &Result, bool isIfndef,
   }
 
   // Should we include the stuff contained by this directive?
-  if (!MI == isIfndef) {
+  if (PPOpts->SingleFileParseMode && !MI) {
+    // In 'single-file-parse mode' undefined identifiers trigger parsing of all
+    // the directive blocks.
+    CurPPLexer->pushConditionalLevel(DirectiveTok.getLocation(),
+                                     /*wasskip*/false, /*foundnonskip*/false,
+                                     /*foundelse*/false);
+  } else if (!MI == isIfndef) {
     // Yes, remember that we are inside a conditional, then lex the next token.
     CurPPLexer->pushConditionalLevel(DirectiveTok.getLocation(),
                                      /*wasskip*/false, /*foundnonskip*/true,
@@ -2676,7 +2682,8 @@ void Preprocessor::HandleIfDirective(Token &IfToken,
   // Parse and evaluate the conditional expression.
   IdentifierInfo *IfNDefMacro = nullptr;
   const SourceLocation ConditionalBegin = CurPPLexer->getSourceLocation();
-  const bool ConditionalTrue = EvaluateDirectiveExpression(IfNDefMacro);
+  const DirectiveEvalResult DER = EvaluateDirectiveExpression(IfNDefMacro);
+  const bool ConditionalTrue = DER.Conditional;
   const SourceLocation ConditionalEnd = CurPPLexer->getSourceLocation();
 
   // If this condition is equivalent to #ifndef X, and if this is the first
@@ -2695,7 +2702,12 @@ void Preprocessor::HandleIfDirective(Token &IfToken,
                   (ConditionalTrue ? PPCallbacks::CVK_True : PPCallbacks::CVK_False));
 
   // Should we include the stuff contained by this directive?
-  if (ConditionalTrue) {
+  if (PPOpts->SingleFileParseMode && DER.IncludedUndefinedIds) {
+    // In 'single-file-parse mode' undefined identifiers trigger parsing of all
+    // the directive blocks.
+    CurPPLexer->pushConditionalLevel(IfToken.getLocation(), /*wasskip*/false,
+                                     /*foundnonskip*/false, /*foundelse*/false);
+  } else if (ConditionalTrue) {
     // Yes, remember that we are inside a conditional, then lex the next token.
     CurPPLexer->pushConditionalLevel(IfToken.getLocation(), /*wasskip*/false,
                                    /*foundnonskip*/true, /*foundelse*/false);
@@ -2756,6 +2768,14 @@ void Preprocessor::HandleElseDirective(Token &Result) {
   if (Callbacks)
     Callbacks->Else(Result.getLocation(), CI.IfLoc);
 
+  if (PPOpts->SingleFileParseMode && !CI.FoundNonSkip) {
+    // In 'single-file-parse mode' undefined identifiers trigger parsing of all
+    // the directive blocks.
+    CurPPLexer->pushConditionalLevel(CI.IfLoc, /*wasskip*/false,
+                                     /*foundnonskip*/false, /*foundelse*/true);
+    return;
+  }
+
   // Finally, skip the rest of the contents of this block.
   SkipExcludedConditionalBlock(CI.IfLoc, /*Foundnonskip*/true,
                                /*FoundElse*/true, Result.getLocation());
@@ -2791,6 +2811,14 @@ void Preprocessor::HandleElifDirective(Token &ElifToken) {
                     SourceRange(ConditionalBegin, ConditionalEnd),
                     PPCallbacks::CVK_NotEvaluated, CI.IfLoc);
 
+  if (PPOpts->SingleFileParseMode && !CI.FoundNonSkip) {
+    // In 'single-file-parse mode' undefined identifiers trigger parsing of all
+    // the directive blocks.
+    CurPPLexer->pushConditionalLevel(ElifToken.getLocation(), /*wasskip*/false,
+                                     /*foundnonskip*/false, /*foundelse*/false);
+    return;
+  }
+
   // Finally, skip the rest of the contents of this block.
   SkipExcludedConditionalBlock(CI.IfLoc, /*Foundnonskip*/true,
                                /*FoundElse*/CI.FoundElse,