From: Ted Kremenek <kremenek@apple.com>
Date: Tue, 19 Oct 2010 22:15:20 +0000 (+0000)
Subject: Really^2 fix <rdar://problem/8361834>, this time without crashing.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=9714a2385cb66b6efa373fc668641de602dd9adb;p=clang

Really^2 fix <rdar://problem/8361834>, this time without crashing.

Now MICache is a linked list (per the FIXME), where we tradeoff between MacroInfo objects being in MICache
and MIChainHead.  MacroInfo objects in the MICache chain are already "Destroy()'ed", so they can be reused.  When
inserting into MICache, we need to remove them from the regular linked list so that they aren't destroyed more than
once.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@116869 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/include/clang/Lex/Preprocessor.h b/include/clang/Lex/Preprocessor.h
index a1a68dce45..42e2daac2f 100644
--- a/include/clang/Lex/Preprocessor.h
+++ b/include/clang/Lex/Preprocessor.h
@@ -195,11 +195,6 @@ class Preprocessor {
   /// to the actual definition of the macro.
   llvm::DenseMap<IdentifierInfo*, MacroInfo*> Macros;
 
-  /// MICache - A "freelist" of MacroInfo objects that can be reused for quick
-  /// allocation.
-  /// FIXME: why not use a singly linked list?
-  std::vector<MacroInfo*> MICache;
-
   /// MacroArgCache - This is a "freelist" of MacroArg objects that can be
   /// reused for quick allocation.
   MacroArgs *MacroArgCache;
@@ -255,12 +250,17 @@ private:  // Cached tokens state.
   struct MacroInfoChain {
     MacroInfo MI;
     MacroInfoChain *Next;
+    MacroInfoChain *Prev;
   };
 
   /// MacroInfos are managed as a chain for easy disposal.  This is the head
   /// of that list.
   MacroInfoChain *MIChainHead;
 
+  /// MICache - A "freelist" of MacroInfo objects that can be reused for quick
+  /// allocation.
+  MacroInfoChain *MICache;
+
 public:
   Preprocessor(Diagnostic &diags, const LangOptions &opts,
                const TargetInfo &target,
diff --git a/lib/Lex/PPDirectives.cpp b/lib/Lex/PPDirectives.cpp
index b958d9e489..8f66d99b18 100644
--- a/lib/Lex/PPDirectives.cpp
+++ b/lib/Lex/PPDirectives.cpp
@@ -28,18 +28,23 @@ using namespace clang;
 //===----------------------------------------------------------------------===//
 
 MacroInfo *Preprocessor::AllocateMacroInfo() {
-  MacroInfo *MI;
+  MacroInfoChain *MIChain;
 
-  if (!MICache.empty()) {
-    MI = MICache.back();
-    MICache.pop_back();
-  } else {
-    MacroInfoChain *MIChain = BP.Allocate<MacroInfoChain>();
-    MIChain->Next = MIChainHead;
-    MIChainHead = MIChain;
-    MI = &(MIChain->MI);
+  if (MICache) {
+    MIChain = MICache;
+    MICache = MICache->Next;
   }
-  return MI;
+  else {
+    MIChain = BP.Allocate<MacroInfoChain>();
+  }
+
+  MIChain->Next = MIChainHead;
+  MIChain->Prev = 0;
+  if (MIChainHead)
+    MIChainHead->Prev = MIChain;
+  MIChainHead = MIChain;
+
+  return &(MIChain->MI);
 }
 
 MacroInfo *Preprocessor::AllocateMacroInfo(SourceLocation L) {
@@ -57,10 +62,23 @@ MacroInfo *Preprocessor::CloneMacroInfo(const MacroInfo &MacroToClone) {
 /// ReleaseMacroInfo - Release the specified MacroInfo.  This memory will
 ///  be reused for allocating new MacroInfo objects.
 void Preprocessor::ReleaseMacroInfo(MacroInfo *MI) {
-  MICache.push_back(MI);
-  MI->FreeArgumentList();
-}
+  MacroInfoChain *MIChain = (MacroInfoChain*) MI;
+  if (MacroInfoChain *Prev = MIChain->Prev) {
+    MacroInfoChain *Next = MIChain->Next;
+    Prev->Next = Next;
+    if (Next)
+      Next->Prev = Prev;
+  }
+  else {
+    assert(MIChainHead == MIChain);
+    MIChainHead = MIChain->Next;
+    MIChainHead->Prev = 0;
+  }
+  MIChain->Next = MICache;
+  MICache = MIChain;
 
+  MI->Destroy();
+}
 
 /// DiscardUntilEndOfDirective - Read and discard all tokens remaining on the
 /// current line until the tok::eom token is found.
diff --git a/lib/Lex/Preprocessor.cpp b/lib/Lex/Preprocessor.cpp
index a0782aa868..1be22df6b1 100644
--- a/lib/Lex/Preprocessor.cpp
+++ b/lib/Lex/Preprocessor.cpp
@@ -56,7 +56,8 @@ Preprocessor::Preprocessor(Diagnostic &diags, const LangOptions &opts,
     SourceMgr(SM), HeaderInfo(Headers), ExternalSource(0),
     Identifiers(opts, IILookup), BuiltinInfo(Target), CodeComplete(0),
     CodeCompletionFile(0), SkipMainFilePreamble(0, true), CurPPLexer(0), 
-    CurDirLookup(0), Callbacks(0), MacroArgCache(0), Record(0), MIChainHead(0) {
+    CurDirLookup(0), Callbacks(0), MacroArgCache(0), Record(0), MIChainHead(0),
+    MICache(0) {
   ScratchBuf = new ScratchBuffer(SourceMgr);
   CounterValue = 0; // __COUNTER__ starts at 0.
   OwnsHeaderSearch = OwnsHeaders;