Predefined Macros

__FILE__

The name of the current source file. __FILE__ expands to a string surrounded by double quotation marks. To ensure that the full path to the file is displayed, use /FC (Full Path of Source Code File in Diagnostics).

__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.

__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.

_CHAR_UNSIGNED

Default char type is unsigned. Defined when /J is specified.

__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;
}

_CPPRTTI

Defined for code compiled with /GR (Enable Run-Time Type Information).

_DEBUG

Defined when you compile with /LDd, /MDd, and /MTd.

__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)
}

__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.

_M_ALPHA

Defined for DEC ALPHA platforms (no longer supported).

_M_CEE

Defined for a compilation that uses any form of /clr (/clr:oldSyntax, /clr:safe, for example).

_M_CEE_SAFE

Defined for a compilation that uses /clr:safe.

_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:IA32 was used.

• 1 if /arch:SSE was used.

• 2 if /arch:SSE2 was used. This value is the default if /arch was not specified.

• See /arch (x86) for more information.

_M_MRX000

Defined for MIPS platforms (no longer supported).

_M_X64

Defined for x64 processors.

_MFC_VER

Defines the MFC version. For example, in Visual Studio 2012, _MFC_VER is defined as 0x0B00.

_MSC_EXTENSIONS

This macro is defined when you compile with the /Ze compiler option (the default). Its value, when defined, is 1.

_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 Visual C++ compiler is 17.00.51106.1, the _MSC_VER macro evaluates to 1700.

_MT

Defined when /MD or /MDd (Multithreaded DLL) or /MT or /MTd (Multithreaded) is specified.

_OPENMP

Defined when compiling 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);
}

_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.

_WIN64

Defined for applications for Win64.

Pentium

/G5

_M_IX86 = 500

80386

/G3

_M_IX86 = 300