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 listed in this article are defined with multiple values.
| 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 surrounded by double quotation marks. To ensure that the full path to the file is displayed, use . |
| __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 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. |
| Macro | Description |
|---|---|
| _ATL_VER | Defines the ATL version.
|
| __AVX__ | Defined when /arch:AVX is specified. |
| _CHAR_UNSIGNED | Default char type is unsigned. Defined when 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,
// clr_ver.cpp// compile with: /clrusing 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} |
| __cplusplus_winrt | Defined when you use the /ZW option to compile. The value of __cplusplus_winrt is 201009. |
| __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. C++ // initialize object with a read-only unique IDexampleClass::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. C++ // 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 (Enable Run-Time Type Information). |
| _CPPUNWIND | Defined for code compiled by using one of the flags. |
| _DEBUG | Defined when you compile with , , and . |
| _DLL | Defined when (Multithreaded DLL) is specified. |
| __FUNCDNAME__ | Valid only in a function. Defines the of the enclosing function as a string. __FUNCDNAME__ is not expanded if you use the or compiler option. The following example uses the __FUNCDNAME__, __FUNCSIG__, and __FUNCTION__ macros to display function information. C++ // 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 or 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 or compiler option. See __FUNCDNAME__ for an example. |
| _INTEGRAL_MAX_BITS | Reports the maximum size (in bits) for an integral type. // integral_max_bits.cpp#include |
| _M_ALPHA | Defined for DEC ALPHA platforms (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_ARM_FP | Expands to a value indicating which /arch compiler option was used:
|
| _M_IX86_FP | Expands to a value indicating which /arch compiler option was used:
|
| _M_MPPC | Defined for Power Macintosh platforms (no longer supported). |
| _M_MRX000 | Defined for MIPS platforms (no longer supported). |
| _M_PPC | Defined for PowerPC platforms (no longer supported). |
| _M_X64 | Defined for x64 processors. |
| _MANAGED | Defined to be 1 when is specified. |
| _MFC_VER | Defines the MFC version. |
| _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 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 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 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 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.
|
| __MSVC_RUNTIME_CHECKS | Defined when one of the compiler options is specified. |
| _MT | Defined when (Multithreaded DLL) or (Multithreaded) is specified. |
| _NATIVE_WCHAR_T_DEFINED | Defined when is used. |
| _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 |
| _VC_NODEFAULTLIB | Defined when /Zl is used; see for more information. |
| _WCHAR_T_DEFINED | Defined when 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 . |
As shown in following table, the compiler generates a value for the preprocessor identifiers that reflect the processor option specified.
| 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 |