Predefined Macros

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Names 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 below are defined with multiple values. See the following tables for more information.

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 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).

You can create your own wide string version of __FILE__ as follows:

#include <stdio.h>
#define WIDEN2(x) L ## x
#define WIDEN(x) WIDEN2(x)
#define __WFILE__ WIDEN(__FILE__)
wchar_t *pwsz = __WFILE__;
int main() {}

__LINE__

The line number in the current source file. The line number is a decimal integer constant. It can be altered 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.

_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 compiling 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 compiland. __COUNTER__ remembers its state when using precompiled headers. If the last __COUNTER__ value was 4 after building a precompiled header (PCH), it will start with 5 on each PCH use.

__COUNTER__ lets you generate unique variable names. You can use token pasting with a prefix to make a unique name. For example:

// pre_mac_counter.cpp
#include <stdio.h>
#define FUNC2(x,y) x##y
#define FUNC1(x,y) FUNC2(x,y)
#define FUNC(x) FUNC1(x,__COUNTER__)
int FUNC(my_unique_prefix);
int FUNC(my_unique_prefix);
int main() {
   my_unique_prefix0 = 0;
   printf_s("\n%d",my_unique_prefix0);
   my_unique_prefix0++;
   printf_s("\n%d",my_unique_prefix0);
}

__cplusplus

Defined for C++ programs only.

_CPPLIB_VER

Defined if you include any of the C++ Standard Library headers; reports which version of the Dinkumware header files are present.

_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 compiling with /LDd, /MDd, and /MTd.

_DLL

Defined when /MD or /MDd (Multithread DLL) is specified.

__FUNCDNAME__

Valid only within a function and returns the decorated name of the enclosing function (as a string). __FUNCDNAME__ is not expanded if you use the /EP or /P compiler option.

__FUNCSIG__

Valid only within a function and returns 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.

__FUNCTION__

Valid only within a function and returns the undecorated name of the enclosing function (as a string). __FUNCTION__ is not expanded if you use the /EP or /P compiler option.

_INTEGRAL_MAX_BITS

Reports 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 platforms (no longer supported).

_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 Values for _M_IX86 for more details.

_M_IA64

Defined for Itanium Processor Family 64-bit processors.

_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 /clr is specified.

_MFC_VER

Defines the MFC version. For example, 0x0700 represents MFC version 7.

_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 compiling 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.

__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, 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

Concepts

Macros (C/C++)

Preprocessor Operators

Preprocessor Directives