Predefined Macros

Lists the predefined ANSI/ISO C99 and Microsoft C++ implementation preprocessor macros.

The compiler recognizes predefined ANSI/ISO C99 C preprocessor macros, and the Microsoft C++ implementation provides several more. These preprocessor macros take no arguments and cannot be redefined. Some of the predefined macros listed in this article 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 literal. To ensure that the full path to the file is displayed, use /FC (Full Path of Source Code File in Diagnostics).
__func__	Returns the unqualified and unadorned name of the enclosing function as an array of char. void Foo(){ printf("%s\n", __func__); } // prints “Foo”
__LINE__	The line number in the current source file. The line number is a decimal integer literal. It can be changed with a #line directive.
__STDC__	Indicates conformance with the ANSI/ISO C99 standard. Defined as the integer literal 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, encoded as an integer literal.
__AVX__	Defined when /arch:AVX or /arch:AVX2 is specified.
__AVX2__	Defined when /arch:AVX2 is specified.
_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 is an integer literal encoded 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 the integer literal 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 }
__cplusplus_winrt	Defined when you use the /ZW option to compile. The value of __cplusplus_winrt is the integer literal 201009.
__COUNTER__	Expands to an integer literal 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 by using one of the /EH (Exception Handling Model) flags.
_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 literal. __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 literal. __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 literal. __FUNCTION__ is not expanded if you use the /EP or /P compiler option. See __FUNCDNAME__ for an example.
_INTEGRAL_MAX_BITS	Reports the maximum size (in bits) for an integral type as an integer literal. // integral_max_bits.cpp #include <stdio.h> int main() { printf("%d\n", _INTEGRAL_MAX_BITS); }
_M_AMD64	Defined for compilations that target x64 processors.
_M_ARM	Defined for compilations that target ARM 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 compilations that target x86 processors. This is not defined for x64 processors.
_M_ARM_FP	Expands to an integer literal value indicating which /arch compiler option was used: In the range 30-39 if no /arch ARM option was specified, indicating the default architecture for ARM was used (VFPv3). In the range 40-49 if /arch:VFPv4 was used. See /arch (x86) for more information.
_M_IX86_FP	Expands to an integer literal value indicating which /arch compiler option was used: 0 if /arch:IA32 was used. 1 if /arch:SSE was used. 2 if /arch:SSE2, /arch:AVX or /arch:AVX2 was used. This value is the default if /arch was not specified. When /arch:AVX is specified, the macro __AVX__ is also defined. When /arch:AVX2 is specified, __AVX__ and __AVX2__ are also defined. See /arch (x86) for more information.
_M_X64	Defined for compilations that target x64 processors.
_MANAGED	Defined to be 1 when /clr is specified.
_MFC_VER	Defines the MFC version, encoded as an integer literal.
_MSC_BUILD	Evaluates to an integer literal that contains 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 Visual C++ 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 an integer literal that encodes 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 Visual C++ 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 an integer literal that encodes 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 Visual C++ compiler is 17.00.51106.1, the _MSC_VER macro evaluates to 1700. Type cl /? at the command line to view the compiler's version number.
__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 compiling with /openmp, evaluates to an integer literal 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.

See Also

Reference

Macros (C/C++)

Preprocessor Operators

Preprocessor Directives