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.

llvm-svn: 116869

2 files changed, 33 insertions, 14 deletions

diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
index b958d9e489f..8f66d99b187 100644
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/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/clang/lib/Lex/Preprocessor.cpp b/clang/lib/Lex/Preprocessor.cpp
index a0782aa8681..1be22df6b1c 100644
--- a/clang/lib/Lex/Preprocessor.cpp
+++ b/clang/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;