The basic abstraction for the target C++ ABI. More...

#include <TargetCXXABI.h>

Public Types
enum	Kind { GenericItanium, GenericARM, iOS, iOS64, GenericAArch64, Microsoft }
	The basic C++ ABI kind. More...
enum	TailPaddingUseRules { AlwaysUseTailPadding, UseTailPaddingUnlessPOD03, UseTailPaddingUnlessPOD11 }
Public Member Functions
	TargetCXXABI ()
	A bogus initialization of the platform ABI.
	TargetCXXABI (Kind kind)
void	set (Kind kind)
Kind	getKind () const
bool	isItaniumFamily () const
	Does this ABI generally fall into the Itanium family of ABIs?
bool	isMicrosoft () const
	Is this ABI an MSVC-compatible ABI?
bool	isMemberFunctionCCDefault () const
	Is the default C++ member function calling convention the same as the default calling convention?
bool	areArgsDestroyedLeftToRightInCallee () const
bool	hasConstructorVariants () const
	Does this ABI have different entrypoints for complete-object and base-subobject constructors?
bool	hasPrimaryVBases () const
	Does this ABI allow virtual bases to be primary base classes?
bool	hasKeyFunctions () const
	Does this ABI use key functions? If so, class data such as the vtable is emitted with strong linkage by the TU containing the key function.
bool	canKeyFunctionBeInline () const
	Can an out-of-line inline function serve as a key function?
TailPaddingUseRules	getTailPaddingUseRules () const
bool	tryParse (llvm::StringRef name)
	Try to parse an ABI name, returning false on error.
Friends
bool	operator== (const TargetCXXABI &left, const TargetCXXABI &right)
bool	operator!= (const TargetCXXABI &left, const TargetCXXABI &right)

Detailed Description

The basic abstraction for the target C++ ABI.

Definition at line 25 of file TargetCXXABI.h.

Member Enumeration Documentation

enum clang::TargetCXXABI::Kind

The basic C++ ABI kind.

Enumerator:

GenericItanium	The generic Itanium ABI is the standard ABI of most open-source and Unix-like platforms. It is the primary ABI targeted by many compilers, including Clang and GCC. It is documented here: http://www.codesourcery.com/public/cxx-abi/
GenericARM	The generic ARM ABI is a modified version of the Itanium ABI proposed by ARM for use on ARM-based platforms. These changes include: the representation of member function pointers is adjusted to not conflict with the 'thumb' bit of ARM function pointers; constructors and destructors return 'this'; guard variables are smaller; inline functions are never key functions; array cookies have a slightly different layout; additional convenience functions are specified; and more! It is documented here: http://infocenter.arm.com /help/topic/com.arm.doc.ihi0041c/IHI0041C_cppabi.pdf
iOS	The iOS ABI is a partial implementation of the ARM ABI. Several of the features of the ARM ABI were not fully implemented in the compilers that iOS was launched with. Essentially, the iOS ABI includes the ARM changes to: member function pointers, guard variables, array cookies, and constructor/destructor signatures.
iOS64	The iOS 64-bit ABI is follows ARM's published 64-bit ABI more closely, but we don't guarantee to follow it perfectly. It is documented here: http://infocenter.arm.com /help/topic/com.arm.doc.ihi0059a/IHI0059A_cppabi64.pdf
GenericAArch64	The generic AArch64 ABI is also a modified version of the Itanium ABI, but it has fewer divergences than the 32-bit ARM ABI. The relevant changes from the generic ABI in this case are: representation of member function pointers adjusted as in ARM. guard variables are smaller.
Microsoft	The Microsoft ABI is the ABI used by Microsoft Visual Studio (and compatible compilers). FIXME: should this be split into Win32 and Win64 variants? Only scattered and incomplete official documentation exists.

Definition at line 28 of file TargetCXXABI.h.

enum clang::TargetCXXABI::TailPaddingUseRules

When is record layout allowed to allocate objects in the tail padding of a base class?

This decision cannot be changed without breaking platform ABI compatibility, and yet it is tied to language guarantees which the committee has so far seen fit to strengthen no less than three separate times:

originally, there were no restrictions at all;
C++98 declared that objects could not be allocated in the tail padding of a POD type;
C++03 extended the definition of POD to include classes containing member pointers; and
C++11 greatly broadened the definition of POD to include all trivial standard-layout classes. Each of these changes technically took several existing platforms and made them permanently non-conformant.

Enumerator:

AlwaysUseTailPadding	The tail-padding of a base class is always theoretically available, even if it's POD. This is not strictly conforming in any language mode.
UseTailPaddingUnlessPOD03	Only allocate objects in the tail padding of a base class if the base class is not POD according to the rules of C++ TR1. This is non-strictly conforming in C++11 mode.
UseTailPaddingUnlessPOD11	Only allocate objects in the tail padding of a base class if the base class is not POD according to the rules of C++11.

Definition at line 236 of file TargetCXXABI.h.

Constructor & Destructor Documentation

clang::TargetCXXABI::TargetCXXABI ( ) [inline]

A bogus initialization of the platform ABI.

Definition at line 99 of file TargetCXXABI.h.

clang::TargetCXXABI::TargetCXXABI ( Kind kind ) [inline]

Definition at line 101 of file TargetCXXABI.h.

Member Function Documentation

bool clang::TargetCXXABI::areArgsDestroyedLeftToRightInCallee ( ) const [inline]

Are arguments to a call destroyed left to right in the callee? This is a fundamental language change, since it implies that objects passed by value do *not* live to the end of the full expression. Temporaries passed to a function taking a const reference live to the end of the full expression as usual. Both the caller and the callee must have access to the destructor, while only the caller needs the destructor if this is false.

Definition at line 155 of file TargetCXXABI.h.

References isMicrosoft().

Referenced by clang::Sema::CheckParmsForFunctionDef(), deactivateArgCleanupsBeforeCall(), clang::CodeGen::CodeGenFunction::EmitCallArg(), clang::CodeGen::CodeGenFunction::EmitCallArgs(), and clang::CodeGen::CodeGenFunction::EmitParmDecl().

bool clang::TargetCXXABI::canKeyFunctionBeInline ( ) const [inline]

Can an out-of-line inline function serve as a key function?

This flag is only useful in ABIs where type data (for example, v-tables and type_info objects) are emitted only after processing the definition of a special "key" virtual function. (This is safe because the ODR requires that every virtual function be defined somewhere in a program.) This usually permits such data to be emitted in only a single object file, as opposed to redundantly in every object file that requires it.

One simple and common definition of "key function" is the first virtual function in the class definition which is not defined there. This rule works very well when that function has a non-inline definition in some non-header file. Unfortunately, when that function is defined inline, this rule requires the type data to be emitted weakly, as if there were no key function.

The ARM ABI observes that the ODR provides an additional guarantee: a virtual function is always ODR-used, so if it is defined inline, that definition must appear in every translation unit that defines the class. Therefore, there is no reason to allow such functions to serve as key functions.

Because this changes the rules for emitting type data, it can cause type data to be emitted with both weak and strong linkage, which is not allowed on all platforms. Therefore, exploiting this observation requires an ABI break and cannot be done on a generic Itanium platform.

Definition at line 205 of file TargetCXXABI.h.

References GenericAArch64, GenericARM, GenericItanium, getKind(), iOS, iOS64, and Microsoft.

Referenced by clang::Sema::CheckFunctionDeclaration(), and computeKeyFunction().

Kind clang::TargetCXXABI::getKind ( ) const [inline]

Definition at line 107 of file TargetCXXABI.h.

Referenced by canKeyFunctionBeInline(), createCXXABI(), clang::CodeGen::CreateItaniumCXXABI(), clang::ASTContext::createMangleContext(), getTailPaddingUseRules(), isItaniumFamily(), and isMicrosoft().

TailPaddingUseRules clang::TargetCXXABI::getTailPaddingUseRules ( ) const [inline]

Definition at line 251 of file TargetCXXABI.h.

References AlwaysUseTailPadding, GenericAArch64, GenericARM, GenericItanium, getKind(), iOS, iOS64, Microsoft, UseTailPaddingUnlessPOD03, and UseTailPaddingUnlessPOD11.

Referenced by mustSkipTailPadding().

bool clang::TargetCXXABI::hasConstructorVariants ( ) const [inline]

Does this ABI have different entrypoints for complete-object and base-subobject constructors?