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List:       cfe-commits
Subject:    [PATCH] D19771: Rework FixedSizeTemplateParameterListStorage
From:       Hubert Tong via cfe-commits <cfe-commits () lists ! llvm ! org>
Date:       2016-04-30 22:15:21
Message-ID: differential-rev-PHID-DREV-ax6rcchxmq7oxl27uyzn-req () reviews ! llvm ! org
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hubert.reinterpretcast created this revision.
hubert.reinterpretcast added reviewers: rsmith, faisalv, aaron.ballman.
hubert.reinterpretcast added subscribers: nwilson, cfe-commits.

This change replaces the custom FixedSizeTemplateParameterListStorage implementation \
with one that follows the interface provided by llvm::TrailingObjects.

http://reviews.llvm.org/D19771

Files:
  include/clang/AST/DeclTemplate.h

Index: include/clang/AST/DeclTemplate.h
===================================================================
--- include/clang/AST/DeclTemplate.h
+++ include/clang/AST/DeclTemplate.h
@@ -141,31 +141,18 @@
 
 /// \brief Stores a list of template parameters for a TemplateDecl and its
 /// derived classes. Suitable for creating on the stack.
-template <size_t N> class FixedSizeTemplateParameterListStorage {
-  // This is kinda ugly: TemplateParameterList usually gets allocated
-  // in a block of memory with NamedDecls appended to it. Here, to get
-  // it stack allocated, we include the params as a separate
-  // variable. After allocation, the TemplateParameterList object
-  // treats them as part of itself.
-  TemplateParameterList List;
-  NamedDecl *Params[N];
+template <size_t N>
+class FixedSizeTemplateParameterListStorage
+    : public TemplateParameterList::FixedSizeStorageOwner {
+  TemplateParameterList::FixedSizeStorage<NamedDecl *>::_<N> storage;
 
 public:
   FixedSizeTemplateParameterListStorage(SourceLocation TemplateLoc,
                                         SourceLocation LAngleLoc,
                                         ArrayRef<NamedDecl *> Params,
                                         SourceLocation RAngleLoc)
-      : List(TemplateLoc, LAngleLoc, Params, RAngleLoc) {
-    // Because we're doing an evil layout hack above, have some
-    // asserts, just to double-check everything is laid out like
-    // expected.
-    assert(sizeof(*this) ==
-               TemplateParameterList::totalSizeToAlloc<NamedDecl *>(N) &&
-           "Object layout not as expected");
-    assert(this->Params == List.getTrailingObjects<NamedDecl *>() &&
-           "Object layout not as expected");
-  }
-  TemplateParameterList *get() { return &List; }
+      : FixedSizeStorageOwner(new (static_cast<void *>(&storage))
+            TemplateParameterList(TemplateLoc, LAngleLoc, Params, RAngleLoc)) {}
 };
 
 /// \brief A template argument list.


["D19771.55726.patch" (text/x-patch)]

Index: include/clang/AST/DeclTemplate.h
===================================================================
--- include/clang/AST/DeclTemplate.h
+++ include/clang/AST/DeclTemplate.h
@@ -141,31 +141,18 @@
 
 /// \brief Stores a list of template parameters for a TemplateDecl and its
 /// derived classes. Suitable for creating on the stack.
-template <size_t N> class FixedSizeTemplateParameterListStorage {
-  // This is kinda ugly: TemplateParameterList usually gets allocated
-  // in a block of memory with NamedDecls appended to it. Here, to get
-  // it stack allocated, we include the params as a separate
-  // variable. After allocation, the TemplateParameterList object
-  // treats them as part of itself.
-  TemplateParameterList List;
-  NamedDecl *Params[N];
+template <size_t N>
+class FixedSizeTemplateParameterListStorage
+    : public TemplateParameterList::FixedSizeStorageOwner {
+  TemplateParameterList::FixedSizeStorage<NamedDecl *>::_<N> storage;
 
 public:
   FixedSizeTemplateParameterListStorage(SourceLocation TemplateLoc,
                                         SourceLocation LAngleLoc,
                                         ArrayRef<NamedDecl *> Params,
                                         SourceLocation RAngleLoc)
-      : List(TemplateLoc, LAngleLoc, Params, RAngleLoc) {
-    // Because we're doing an evil layout hack above, have some
-    // asserts, just to double-check everything is laid out like
-    // expected.
-    assert(sizeof(*this) ==
-               TemplateParameterList::totalSizeToAlloc<NamedDecl *>(N) &&
-           "Object layout not as expected");
-    assert(this->Params == List.getTrailingObjects<NamedDecl *>() &&
-           "Object layout not as expected");
-  }
-  TemplateParameterList *get() { return &List; }
+      : FixedSizeStorageOwner(new (static_cast<void *>(&storage))
+            TemplateParameterList(TemplateLoc, LAngleLoc, Params, RAngleLoc)) {}
 };
 
 /// \brief A template argument list.

[Attachment #4 (text/plain)]

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