Region-allocate all AttributeList objects from a factory object instead of manually managing them

using new/delete and OwningPtrs.  After memory profiling Clang, I witnessed periodic leaks of these
objects; digging deeper into the code, it was clear that our management of these objects was a mess.  The ownership rules were murky at best, and not always followed.  Worse, there are plenty of error paths where we could screw up.

This patch introduces AttributeList::Factory, which is a factory class that creates AttributeList
objects and then blows them away all at once.  While conceptually simple, most of the changes in
this patch just have to do with migrating over to the new interface.  Most of the changes have resulted in some nice simplifications.

This new strategy currently holds on to all AttributeList objects during the lifetime of the Parser
object.  This is easily tunable.  If we desire to have more bound the lifetime of AttributeList
objects more precisely, we can have the AttributeList::Factory object (in Parser) push/pop its
underlying allocator as we enter/leave key methods in the Parser.  This means that we get
simple memory management while still having the ability to finely control memory use if necessary.

Note that because AttributeList objects are now BumpPtrAllocated, we may reduce malloc() traffic
in many large files with attributes.

This fixes the leak reported in: <rdar://problem/8650003>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@118675 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 28 insertions, 5 deletions

diff --git a/include/clang/Sema/AttributeList.h b/include/clang/Sema/AttributeList.h
index 5cdfb9484e..1a4f38204b 100644
--- a/include/clang/Sema/AttributeList.h
+++ b/include/clang/Sema/AttributeList.h
@@ -15,6 +15,7 @@
 #ifndef LLVM_CLANG_SEMA_ATTRLIST_H
 #define LLVM_CLANG_SEMA_ATTRLIST_H
 
+#include "llvm/Support/Allocator.h"
 #include "clang/Sema/Ownership.h"
 #include "clang/Basic/SourceLocation.h"
 #include <cassert>
@@ -32,6 +33,9 @@ namespace clang {
 /// 4: __attribute__(( aligned(16) )). ParmName is unused, Args/Num used.
 ///
 class AttributeList {
+public:
+  class Factory;
+private:
   IdentifierInfo *AttrName;
   SourceLocation AttrLoc;
   IdentifierInfo *ScopeName;
@@ -45,14 +49,33 @@ class AttributeList {
   mutable bool Invalid; /// True if already diagnosed as invalid.
   AttributeList(const AttributeList &); // DO NOT IMPLEMENT
   void operator=(const AttributeList &); // DO NOT IMPLEMENT
-public:
-  AttributeList(IdentifierInfo *AttrName, SourceLocation AttrLoc,
+  void operator delete(void *); // DO NOT IMPLEMENT
+  ~AttributeList(); // DO NOT IMPLEMENT
+  AttributeList(llvm::BumpPtrAllocator &Alloc,
+                IdentifierInfo *AttrName, SourceLocation AttrLoc,
                 IdentifierInfo *ScopeName, SourceLocation ScopeLoc,
                 IdentifierInfo *ParmName, SourceLocation ParmLoc,
                 Expr **args, unsigned numargs,
-                AttributeList *Next, bool declspec = false, bool cxx0x = false);
-  ~AttributeList();
-
+                AttributeList *Next, bool declspec, bool cxx0x);
+public:
+  class Factory {
+    llvm::BumpPtrAllocator Alloc;
+  public:
+    Factory() {}
+    ~Factory() {}
+    AttributeList *Create(IdentifierInfo *AttrName, SourceLocation AttrLoc,
+      IdentifierInfo *ScopeName, SourceLocation ScopeLoc,
+      IdentifierInfo *ParmName, SourceLocation ParmLoc,
+      Expr **args, unsigned numargs,
+      AttributeList *Next, bool declspec = false, bool cxx0x = false) {
+        AttributeList *Mem = Alloc.Allocate<AttributeList>();
+        new (Mem) AttributeList(Alloc, AttrName, AttrLoc, ScopeName, ScopeLoc,
+                                ParmName, ParmLoc, args, numargs,
+                                Next, declspec, cxx0x);
+        return Mem;
+      }
+  };
+  
   enum Kind {             // Please keep this list alphabetized.
     AT_IBAction,          // Clang-specific.
     AT_IBOutlet,          // Clang-specific.