Predefined Macros

Lists the predefined ANSI C and Microsoft C++ implementation macros.

The compiler recognizes predefined ANSI C macros and the Microsoft C++ implementation provides several more. These macros take no arguments and cannot be redefined. Some of the predefined macros in the following tables are defined with multiple values.

ANSI-Compliant Predefined Macros

Macro	Description
__DATE__	The compilation date of the current source file. The date is a string literal of the form Mmm dd yyyy. The month name Mmm is the same as for dates generated by the library function asctime declared in TIME.H.
__FILE__	The name of the current source file. __FILE__ expands to a string enclosed in double quotation marks. To make sure that the full path of the file is displayed, use /FC (Full Path of Source Code File in Diagnostics).
__LINE__	The line number in the current source file. The line number is a decimal integer constant. It can be changed with a #line directive.
__STDC__	Indicates full conformance with the ANSI C standard. Defined as the integer constant 1 only if the /Za compiler option is given and you are not compiling C++ code; otherwise is undefined.
__TIME__	The most recent compilation time of the current source file. The time is a string literal of the form hh:mm:ss.
__TIMESTAMP__	The date and time of the last modification of the current source file, expressed as a string literal in the form Ddd Mmm Date hh:mm:ss yyyy, where Ddd is the abbreviated day of the week and Date is an integer from 1 to 31.

Microsoft-Specific Predefined Macros

Macro	Description
_ATL_VER	Defines the ATL version. In Visual Studio 2008, _ATL_VER is defined as 0x0900.
_CHAR_UNSIGNED	Default char type is unsigned. Defined when /J is specified.
__CLR_VER	Defines the version of the common language runtime used when the application was compiled. The value returned will be in the following format: Mmmbbbbb where, M is the major version of the runtime mm is the minor version of the runtime bbbbb is the build number. // clr_ver.cpp // compile with: /clr using namespace System; int main() { Console::WriteLine(__CLR_VER); }
__cplusplus_cli	Defined when you compile with /clr, /clr:pure, or /clr:safe. Value of __cplusplus_cli is 200406. __cplusplus_cli is in effect throughout the translation unit. // cplusplus_cli.cpp // compile with: /clr #include "stdio.h" int main() { #ifdef __cplusplus_cli printf("%d\n", __cplusplus_cli); #else printf("not defined\n"); #endif }
__COUNTER__	Expands to an integer starting with 0 and incrementing by 1 every time it is used in a source file or included headers of the source file. __COUNTER__ remembers its state when you use precompiled headers. The following example uses __COUNTER__ to assign unique identifiers to three different objects of the same type. First, assume the following class definition. The constructor takes an integer as a parameter. // initialize object with a read-only unique ID exampleClass::exampleClass(int nID) { m_nID = nID; } int exampleClass::GetID() { return m_nID; } In main, the application declares three objects of type exampleClass, using __COUNTER__ as the unique identifier parameter. // Demonstration of __COUNTER__, assigns unique identifiers to  // different objects of the same type  int main(int argc, char** argv) { // __COUNTER__ is initially defined as 0 exampleClass e1(__COUNTER__); // having been referenced, __COUNTER__ is now defined as 1 exampleClass e2(__COUNTER__); // __COUNTER__ is now defined as 2 exampleClass e3(__COUNTER__); printf("e1 ID: %i\n", e1.GetID()); printf("e2 ID: %i\n", e2.GetID()); printf("e3 ID: %i\n", e3.GetID()); // Output  // ------------------------------  // e1 ID: 0  // e2 ID: 1  // e3 ID: 2  return 0; }
__cplusplus	Defined for C++ programs only.
_CPPRTTI	Defined for code compiled with /GR (Enable Run-Time Type Information).
_CPPUNWIND	Defined for code compiled with /GX (Enable Exception Handling).
_DEBUG	Defined when you compile with /LDd, /MDd, and /MTd.
_DLL	Defined when /MD or /MDd (Multithreaded DLL) is specified.
__FUNCDNAME__	Valid only in a function. Defines the decorated name of the enclosing function as a string. __FUNCDNAME__ is not expanded if you use the /EP or /P compiler option. The following example uses the __FUNCDNAME__, __FUNCSIG__, and __FUNCTION__ macros to display function information. // Demonstrates functionality of __FUNCTION__, __FUNCDNAME__, and __FUNCSIG__ macros  void exampleFunction() { printf("Function name: %s\n", __FUNCTION__); printf("Decorated function name: %s\n", __FUNCDNAME__); printf("Function signature: %s\n", __FUNCSIG__); // Sample Output  // -------------------------------------------------  // Function name: exampleFunction  // Decorated function name: ?exampleFunction@@YAXXZ  // Function signature: void __cdecl exampleFunction(void) }
__FUNCSIG__	Valid only in a function. Defines the signature of the enclosing function as a string. __FUNCSIG__ is not expanded if you use the /EP or /P compiler option. On a 64-bit operating system, the calling convention is __cdecl by default. See __FUNCDNAME__ for an example.
__FUNCTION__	Valid only in a function. Defines the undecorated name of the enclosing function as a string. __FUNCTION__ is not expanded if you use the /EP or /P compiler option. See __FUNCDNAME__ for an example.
_INTEGRAL_MAX_BITS	Defines the maximum size (in bits) for an integral type. // integral_max_bits.cpp #include <stdio.h> int main() { printf("%d\n", _INTEGRAL_MAX_BITS); }
_M_ALPHA	Defined for DEC ALPHA operating systems (no longer supported).
_M_AMD64	Defined for x64 processors.
_M_CEE	Defined for a compilation that uses any form of /clr (/clr:oldSyntax, /clr:safe, for example).
_M_CEE_PURE	Defined for a compilation that uses /clr:pure.
_M_CEE_SAFE	Defined for a compilation that uses /clr:safe.
_M_IX86	Defined for x86 processors. See the Values for _M_IX86 table below for more information. This is not defined for x64 processors.
_M_IA64	Defined for Itanium Processor Family 64-bit processors.
_M_IX86_FP	Expands to a value indicating which /arch compiler option was used: 0 if /arch was not used. 1 if /arch:SSE was used. 2 if /arch:SSE2 was used. See /arch (Minimum CPU Architecture) for more information.
_M_MPPC	Defined for Power Macintosh operating systems (no longer supported).
_M_MRX000	Defined for MIPS operating systems (no longer supported).
_M_PPC	Defined for PowerPC operating systems (no longer supported).
_M_X64	Defined for x64 processors.
_MANAGED	Defined to be 1 when /clr is specified.
_MFC_VER	Defines the MFC version. In Visual Studio 2008, _MFC_VER is defined as 0x0900.
_MSC_BUILD	Evaluates to the revision number component of the compiler's version number. The revision number is the fourth component of the period-delimited version number. For example, if the version number of the VC++ compiler is 15.00.20706.01, the _MSC_BUILD macro evaluates to 1.
_MSC_EXTENSIONS	This macro is defined when you compile with the /Ze compiler option (the default). Its value, when defined, is 1.
_MSC_FULL_VER	Evaluates to the major, minor, and build number components of the compiler's version number. The major number is the first component of the period-delimited version number, the minor number is the second component, and the build number is the third component. For example, if the version number of the VC++ compiler is 15.00.20706.01, the _MSC_FULL_VER macro evaluates to 150020706. Type cl /? at the command line to view the compiler's version number.
_MSC_VER	Evaluates to the major and minor number components of the compiler's version number. The major number is the first component of the period-delimited version number and the minor number is the second component. For example, if the version number of the VC++ compiler is 15.00.20706.01, the _MSC_VER macro evaluates to 1500. In Visual Studio 2008, _MSC_VER is defined as 1500.
__MSVC_RUNTIME_CHECKS	Defined when one of the /RTC compiler options is specified.
_MT	Defined when /MD or /MDd (Multithreaded DLL) or /MT or /MTd (Multithreaded) is specified.
_NATIVE_WCHAR_T_DEFINED	Defined when /Zc:wchar_t is used.
_OPENMP	Defined when you compile with /openmp, returns an integer representing the date of the OpenMP specification implemented by Visual C++. // _OPENMP_dir.cpp // compile with: /openmp #include <stdio.h> int main() { printf("%d\n", _OPENMP); }
_VC_NODEFAULTLIB	Defined when /Zl is used; see /Zl (Omit Default Library Name) for more information.
_WCHAR_T_DEFINED	Defined when /Zc:wchar_t is used or if wchar_t is defined in a system header file included in your project.
_WIN32	Defined for applications for Win32 and Win64. Always defined.
_WIN64	Defined for applications for Win64.
_Wp64	Defined when specifying /Wp64.

As shown in following table, the compiler generates a value for the preprocessor identifiers that reflect the processor option specified.

Values for _M_IX86

Option in Development Environment	Command-Line Option	Resulting Value
Blend	/GB	_M_IX86 = 600 (Default. Future compilers will emit a different value to reflect the dominant processor.)
Pentium	/G5	_M_IX86 = 500
Pentium Pro, Pentium II, and Pentium III	/G6	_M_IX86 = 600
80386	/G3	_M_IX86 = 300
80486	/G4	_M_IX86 = 400

See Also

Reference

Macros (C/C+)

Preprocessor Operators

Preprocessor Directives

Change History

Date	History	Reason
March 2009	Updated information in __FILE__ and _M_IX86.	Information enhancement.
May 2009	Added Visual Studio 2008 values for _ATL_VER, _MSC_VER, _MFC_VER; removed _CPPLIB_VER; updated __COUNTER__, _DEBUG, _DLL, _MT, __FUNCDNAME__, __FUNCSIG__, __FUNCTION__, __FILE__. Cleaned up topic.	Customer feedback.
October 2010	Added the _M_AMD64 macro.	Customer feedback.