From a98a95cca735b95cca5c904fa5ca875d916effc1 Mon Sep 17 00:00:00 2001
From: Francois Ferrand <thetypz@gmail.com>
Date: Fri, 28 Jul 2017 07:56:14 +0000
Subject: clang-format: fix block OpeningLineIndex around preprocessor

Summary:
The current code would return an incorrect value when a preprocessor
directive is present immediately after the opening brace: this causes
the nanespace end comment fixer to break in some places, for exemple it
would not add the comment in this case:

  namespace a {
  #define FOO
  }

Fixing the computation is simple enough, but it was breaking a feature,
as it would cause comments to be added also when the namespace
declaration was dependant on conditional compilation.

To fix this, a hash of the current preprocessor stack/branches is
computed at the beginning of parseBlock(), so that we explicitely do not
store the OpeningLineIndex when the beginning and end of the block are
not in the same preprocessor conditions.

Tthe hash is computed based on the line, but this could propbably be
improved by using the actual condition, so that clang-format would be
able to match multiple identical #ifdef blocks.

Reviewers: krasimir, djasper

Reviewed By: krasimir

Subscribers: klimek, cfe-commits

Differential Revision: https://reviews.llvm.org/D35483

llvm-svn: 309369
---
 clang/lib/Format/UnwrappedLineParser.cpp | 54 +++++++++++++++++++++++++-------
 1 file changed, 42 insertions(+), 12 deletions(-)

(limited to 'clang/lib/Format/UnwrappedLineParser.cpp')

diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index 9bb9ed19183..bbed83263ce 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -452,6 +452,21 @@ void UnwrappedLineParser::calculateBraceTypes(bool ExpectClassBody) {
   FormatTok = Tokens->setPosition(StoredPosition);
 }
 
+template <class T>
+static inline void hash_combine(std::size_t &seed, const T &v) {
+  std::hash<T> hasher;
+  seed ^= hasher(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+}
+
+size_t UnwrappedLineParser::computePPHash() const {
+  size_t h = 0;
+  for (const auto &i : PPStack) {
+    hash_combine(h, size_t(i.Kind));
+    hash_combine(h, i.Line);
+  }
+  return h;
+}
+
 void UnwrappedLineParser::parseBlock(bool MustBeDeclaration, bool AddLevel,
                                      bool MunchSemi) {
   assert(FormatTok->isOneOf(tok::l_brace, TT_MacroBlockBegin) &&
@@ -459,16 +474,21 @@ void UnwrappedLineParser::parseBlock(bool MustBeDeclaration, bool AddLevel,
   const bool MacroBlock = FormatTok->is(TT_MacroBlockBegin);
   FormatTok->BlockKind = BK_Block;
 
+  size_t PPStartHash = computePPHash();
+
   unsigned InitialLevel = Line->Level;
   nextToken(/*LevelDifference=*/AddLevel ? 1 : 0);
 
   if (MacroBlock && FormatTok->is(tok::l_paren))
     parseParens();
 
+  size_t NbPreprocessorDirectives =
+      CurrentLines == &Lines ? PreprocessorDirectives.size() : 0;
   addUnwrappedLine();
-  size_t OpeningLineIndex = CurrentLines->empty()
-                                ? (UnwrappedLine::kInvalidIndex)
-                                : (CurrentLines->size() - 1);
+  size_t OpeningLineIndex =
+      CurrentLines->empty()
+          ? (UnwrappedLine::kInvalidIndex)
+          : (CurrentLines->size() - 1 - NbPreprocessorDirectives);
 
   ScopedDeclarationState DeclarationState(*Line, DeclarationScopeStack,
                                           MustBeDeclaration);
@@ -486,6 +506,8 @@ void UnwrappedLineParser::parseBlock(bool MustBeDeclaration, bool AddLevel,
     return;
   }
 
+  size_t PPEndHash = computePPHash();
+
   // Munch the closing brace.
   nextToken(/*LevelDifference=*/AddLevel ? -1 : 0);
 
@@ -495,11 +517,14 @@ void UnwrappedLineParser::parseBlock(bool MustBeDeclaration, bool AddLevel,
   if (MunchSemi && FormatTok->Tok.is(tok::semi))
     nextToken();
   Line->Level = InitialLevel;
-  Line->MatchingOpeningBlockLineIndex = OpeningLineIndex;
-  if (OpeningLineIndex != UnwrappedLine::kInvalidIndex) {
-    // Update the opening line to add the forward reference as well
-    (*CurrentLines)[OpeningLineIndex].MatchingOpeningBlockLineIndex =
-            CurrentLines->size() - 1;
+
+  if (PPStartHash == PPEndHash) {
+    Line->MatchingOpeningBlockLineIndex = OpeningLineIndex;
+    if (OpeningLineIndex != UnwrappedLine::kInvalidIndex) {
+      // Update the opening line to add the forward reference as well
+      (*CurrentLines)[OpeningLineIndex].MatchingOpeningBlockLineIndex =
+          CurrentLines->size() - 1;
+    }
   }
 }
 
@@ -607,10 +632,15 @@ void UnwrappedLineParser::parsePPDirective() {
 }
 
 void UnwrappedLineParser::conditionalCompilationCondition(bool Unreachable) {
-  if (Unreachable || (!PPStack.empty() && PPStack.back() == PP_Unreachable))
-    PPStack.push_back(PP_Unreachable);
+  size_t Line = CurrentLines->size();
+  if (CurrentLines == &PreprocessorDirectives)
+    Line += Lines.size();
+
+  if (Unreachable ||
+      (!PPStack.empty() && PPStack.back().Kind == PP_Unreachable))
+    PPStack.push_back({PP_Unreachable, Line});
   else
-    PPStack.push_back(PP_Conditional);
+    PPStack.push_back({PP_Conditional, Line});
 }
 
 void UnwrappedLineParser::conditionalCompilationStart(bool Unreachable) {
@@ -2400,7 +2430,7 @@ void UnwrappedLineParser::readToken(int LevelDifference) {
       FormatTok->MustBreakBefore = true;
     }
 
-    if (!PPStack.empty() && (PPStack.back() == PP_Unreachable) &&
+    if (!PPStack.empty() && (PPStack.back().Kind == PP_Unreachable) &&
         !Line->InPPDirective) {
       continue;
     }
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