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Predefined C++ Types

Every C and C++ source file compiled with Microsoft Visual C++ has, in effect, a forced inclusion of a header file written by Microsoft to provide some predefined types.

Name

These pre-definitions do not exist as a separate file but are hard-coded into the compiler (C1 or C1XX). A file name of sorts is provided via a #line directive to the preprocessor:

#line 15 "predefined C++ types (compiler internal)"

The significance of starting the “file” at line 15, specifically, is not known.

As an aside, note that although the name speaks of C++ specifically, it applies to both the C and C++ compilers.

Size Type

A type, size_t, is built into the language as the type returned by the sizeof operator and (in C++) as the type required for the first argument of operator new. However, the definition of this type is formally left to header files that are expected to be supplied with the C Run-Time Library (CRT). Microsoft Visual C++ helpfully defines size_t for those programmers who are not using any CRT headers.

The C++ compiler pre-defines size_t no matter what:

#if Wp64

typedef __w64 unsigned int size_t;

#else

typedef unsigned int size_t;

#endif

but the C compiler defines it only conditionally:

#if Wp64

typedef __w64 unsigned int size_t;

#endif

Note that the choice in C++ is governed by the macro Wp64 with no leading underscore, not by the macro _Wp64 that is defined by CL as an implication of the /Wp64 option.

New and Delete Operators (C++ only)

extern __declspec(unmanaged) void * __cdecl operator new(size_t);

extern __declspec(unmanaged) void __cdecl operator delete(void *);

Exception Handling (C++ only)

extern "C" __declspec(unmanaged) int __cdecl atexit(void (__cdecl *)(void));

#pragma pack(push, ehdata, 4)

typedef struct _PMD

{

int mdisp;

int pdisp;

int vdisp;

} _PMD;

typedef void (*_PMFN)(void);

#pragma warning(disable:4200)

#pragma pack(push, _TypeDescriptor, 8)

typedef struct _TypeDescriptor

{

const void * pVFTable;

void * spare;

char name[];

} _TypeDescriptor;

#pragma pack(pop, _TypeDescriptor)

#pragma warning(default:4200)

typedef const struct _s__CatchableType {

unsigned int properties;

_TypeDescriptor *pType;

_PMD thisDisplacement;

int sizeOrOffset;

_PMFN copyFunction;

} _CatchableType;

#pragma warning(disable:4200)

typedef const struct _s__CatchableTypeArray {

int nCatchableTypes;

_CatchableType *arrayOfCatchableTypes[];

} _CatchableTypeArray;

#pragma warning(default:4200)

typedef const struct _s__ThrowInfo {

unsigned int attributes;

_PMFN pmfnUnwind;

int (__cdecl*pForwardCompat)(...);

_CatchableTypeArray *pCatachableTypeArray;

} _ThrowInfo;

__declspec (noreturn) extern "C" void __stdcall _CxxThrowException(void* pExceptionObject, _ThrowInfo* pThrowInfo);

extern "C" int __cdecl __CxxExceptionFilter(void*, void*, int, void *);

extern "C" int __cdecl __CxxRegisterExceptionObject(void *exception, void *storage);

extern "C" int __cdecl __CxxDetectRethrow(void *exception);

extern "C" int __cdecl __CxxQueryExceptionSize(void);

extern "C" void __cdecl __CxxUnregisterExceptionObject(void *storage, int rethrow);

#pragma pack(pop, ehdata)

Run-Time Type Information (C++ only)

#pragma pack(push, rttidata, 4)

typedef const struct _s__RTTIBaseClassDescriptor {

_TypeDescriptor *pTypeDescriptor;

unsigned long numContainedBases;

_PMD where;

unsigned long attributes;

} __RTTIBaseClassDescriptor;

#pragma warning(disable:4200)

typedef const struct _s__RTTIBaseClassArray {

__RTTIBaseClassDescriptor *arrayOfBaseClassDescriptors[];

} __RTTIBaseClassArray;

#pragma warning(default:4200)

typedef const struct _s__RTTIClassHierarchyDescriptor {

unsigned long signature;

unsigned long attributes;

unsigned long numBaseClasses;

__RTTIBaseClassArray *pBaseClassArray;

} __RTTIClassHierarchyDescriptor;

typedef const struct _s__RTTICompleteObjectLocator {

unsigned long signature;

unsigned long offset;

unsigned long cdOffset;

_TypeDescriptor *pTypeDescriptor;

__RTTIClassHierarchyDescriptor *pClassDescriptor;

} __RTTICompleteObjectLocator;

typedef const class type_info &__RTtypeidReturnType;

extern "C" void* __cdecl __RTDynamicCast (

void*,

long,

void*,

int) throw (...);

extern "C" void* __cdecl __RTtypeid (void*) throw (...);

extern "C" void* __cdecl __RTCastToVoid (void*) throw (...);

#pragma pack(pop, rttidata)

GUID (C++ only)

struct __s_GUID {

unsigned long Data1;

unsigned short Data2;

unsigned short Data3;

unsigned char Data4[8];

};

typedef const struct _GUID &__rcGUID_t;

Intrinsics

Functions for which the compiler is to provide its own implementations ordinarily must be declared (with C linkage) before use. For who knows what reason, Microsoft makes exceptions for two of these intrinsics.

For __debugbreak, the C and C++ declarations differ only in that extern "C" is omitted for C.

extern "C"

__declspec(unmanaged) void __cdecl __debugbreak(void);

For __annotation, which Microsoft anyway does not document, the C compiler omits not just the extern "C" but also the alternative declaration in terms of the native wchar_t type.

extern "C"

#if defined(_NATIVE_WCHAR_T_DEFINED)

__declspec(unmanaged) void __cdecl __annotation(const wchar_t *, ...);

#else

__declspec(unmanaged) void __cdecl __annotation(const unsigned short *, ...);

#endif

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