TrailingObjects.h File Reference

This header defines support for implementing classes that have some trailing object (or arrays of objects) appended to them. More...

#include "llvm/Support/AlignOf.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/type_traits.h"
#include <new>
#include <type_traits>

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Classes
class	llvm::trailing_objects_internal::AlignmentCalcHelper< First, Rest >
	Helper template to calculate the max alignment requirement for a set of objects. More...
class	llvm::trailing_objects_internal::AlignmentCalcHelper< First >
class	llvm::trailing_objects_internal::TrailingObjectsBase
	The base class for TrailingObjects* classes. More...
struct	llvm::trailing_objects_internal::TrailingObjectsBase::OverloadToken< T >
	OverloadToken's purpose is to allow specifying function overloads for different types, without actually taking the types as parameters. More...
class	llvm::trailing_objects_internal::TrailingObjectsAligner< Align >
	This helper template works-around MSVC 2013's lack of useful alignas() support. More...
class	llvm::trailing_objects_internal::TrailingObjectsAligner< 1 >
class	llvm::trailing_objects_internal::TrailingObjectsAligner< 2 >
class	llvm::trailing_objects_internal::TrailingObjectsAligner< 4 >
class	llvm::trailing_objects_internal::TrailingObjectsAligner< 8 >
class	llvm::trailing_objects_internal::TrailingObjectsAligner< 16 >
class	llvm::trailing_objects_internal::TrailingObjectsAligner< 32 >
struct	llvm::trailing_objects_internal::ExtractSecondType< Ty1, Ty2 >
class	llvm::trailing_objects_internal::TrailingObjectsImpl< Align, BaseTy, TopTrailingObj, PrevTy, MoreTys >
class	llvm::trailing_objects_internal::TrailingObjectsImpl< Align, BaseTy, TopTrailingObj, PrevTy, NextTy, MoreTys... >
class	llvm::trailing_objects_internal::TrailingObjectsImpl< Align, BaseTy, TopTrailingObj, PrevTy >
class	llvm::TrailingObjects< BaseTy, TrailingTys >
	See the file comment for details on the usage of the TrailingObjects type. More...
struct	llvm::TrailingObjects< BaseTy, TrailingTys >::FixedSizeStorage< Tys >
	A type where its ::with_counts template member has a ::type member suitable for use as uninitialized storage for an object with the given trailing object counts. More...
struct	llvm::TrailingObjects< BaseTy, TrailingTys >::FixedSizeStorage< Tys >::with_counts< Counts >
class	llvm::TrailingObjects< BaseTy, TrailingTys >::FixedSizeStorageOwner
	A type that acts as the owner for an object placed into fixed storage. More...

Namespaces
	llvm
	This class represents lattice values for constants.
	llvm::trailing_objects_internal

Detailed Description

This header defines support for implementing classes that have some trailing object (or arrays of objects) appended to them.

The main purpose is to make it obvious where this idiom is being used, and to make the usage more idiomatic and more difficult to get wrong.

The TrailingObject template abstracts away the reinterpret_cast, pointer arithmetic, and size calculations used for the allocation and access of appended arrays of objects, and takes care that they are all allocated at their required alignment. Additionally, it ensures that the base type is final – deriving from a class that expects data appended immediately after it is typically not safe.

Users are expected to derive from this template, and provide numTrailingObjects implementations for each trailing type except the last, e.g. like this sample:

class VarLengthObj : private TrailingObjects<VarLengthObj, int, double> {
  friend TrailingObjects;

  unsigned NumInts, NumDoubles;
  size_t numTrailingObjects(OverloadToken<int>) const { return NumInts; }
 };

You can access the appended arrays via 'getTrailingObjects', and determine the size needed for allocation via 'additionalSizeToAlloc' and 'totalSizeToAlloc'.

All the methods implemented by this class are are intended for use by the implementation of the class, not as part of its interface (thus, private inheritance is suggested).

Definition in file TrailingObjects.h.