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Predefined macros |
Lists and describes the Microsoft C++ compiler predefined preprocessor macros. |
update_every_version |
06/11/2024 |
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1cc5f70a-a225-469c-aed0-fe766238e23f |
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The Microsoft C/C++ compiler (MSVC) predefines certain preprocessor macros depending on the language (C or C++), the compilation target, and the chosen compiler options.
MSVC supports the predefined preprocessor macros required by the ANSI/ISO C99, C11, and C17 standards, and the ISO C++14, C++17, and C++20 standards. The implementation also supports several more Microsoft-specific preprocessor macros.
Some macros are defined only for specific build environments or compiler options. Except where noted, the macros are defined throughout a translation unit as if they were specified as /D
compiler option arguments. When defined, the preprocessor expands macros their specified values before compilation. The predefined macros take no arguments and can't be redefined.
The compiler supports this predefined identifier specified by ISO C99 and ISO C++11.
-
__func__
The unqualified and unadorned name of the enclosing function as a function-local static const array ofchar
.void example() { printf("%s\n", __func__); } // prints "example"
The compiler supports these predefined macros specified by the ISO C99, C11, C17, and ISO C++17 standards.
-
__cplusplus
Defined as an integer literal value when the translation unit is compiled as C++. Otherwise, undefined. -
__DATE__
The compilation date of the current source file. The date is a constant length string literal of the form Mmm dd yyyy. The month name Mmm is the same as the abbreviated month name generated by the C Runtime Library (CRT) asctime function. The first character of date dd is a space if the value is less than 10. This macro is always defined. -
__FILE__
The name of the current source file.__FILE__
expands to a character string literal. To ensure that the full path to the file is displayed, use/FC
(Full Path of Source Code File in Diagnostics). This macro is always defined. -
__LINE__
Defined as the integer line number in the current source file. The value of this macro can be changed by using a#line
directive. The integral type of the value of__LINE__
can vary depending on context. This macro is always defined. -
__STDC__
Defined as 1 when compiled as C and if the/Za
compiler option is specified. Starting in Visual Studio 2022 version 17.2, it's defined as 1 when compiled as C and if the/std:c11
or/std:c17
compiler option is specified. Otherwise, undefined. -
__STDC_HOSTED__
Defined as 1 if the implementation is a hosted implementation, one that supports the entire required standard library. Otherwise, defined as 0. -
__STDC_NO_ATOMICS__
Defined as 1 if the implementation doesn't support optional standard atomics. The MSVC implementation defines it as 1 when compiled as C and one of the/std
C11 or C17 options is specified. -
__STDC_NO_COMPLEX__
Defined as 1 if the implementation doesn't support optional standard complex numbers. The MSVC implementation defines it as 1 when compiled as C and one of the/std
C11 or C17 options is specified. -
__STDC_NO_THREADS__
Defined as 1 if the implementation doesn't support optional standard threads. The MSVC implementation defines it as 1 when compiled as C and one of the/std
C11 or C17 options is specified. -
__STDC_NO_VLA__
Defined as 1 if the implementation doesn't support standard variable length arrays. The MSVC implementation defines it as 1 when compiled as C and one of the/std
C11 or C17 options is specified. -
__STDC_VERSION__
Defined when compiled as C and one of the/std
C11 or C17 options is specified. It expands to201112L
for/std:c11
, and201710L
for/std:c17
. -
__STDCPP_DEFAULT_NEW_ALIGNMENT__
When/std:c17
or later is specified, this macro expands to asize_t
literal that has the value of the alignment guaranteed by a call to alignment-unawareoperator new
. Larger alignments are passed to an alignment-aware overload, such asoperator new(std::size_t, std::align_val_t)
. For more information, see/Zc:alignedNew
(C++17 over-aligned allocation). -
__STDCPP_THREADS__
Defined as 1 if and only if a program can have more than one thread of execution, and compiled as C++. Otherwise, undefined. -
__TIME__
The time of translation of the preprocessed translation unit. The time is a character string literal of the form hh:mm:ss, the same as the time returned by the CRT asctime function. This macro is always defined.
MSVC supports other predefined macros:
-
__ARM_ARCH
Defined as an integer literal that represents the ARM architecture version. The value is defined as 8 for the Armv8-A architecture. For 8.1 and onwards, the value is scaled for minor versions, such as X.Y, by using the formula X * 100 + Y as defined by the ARM C language extension. For example, for Armv8.1,__ARM_ARCH
is 8 * 100 + 1 or 801. To set the ARM architecture version, see/arch (ARM64)
. This macro was introduced in Visual Studio 2022 version 17.10. -
__ATOM__
Defined as 1 when the/favor:ATOM
compiler option is set and the compiler target is x86 or x64. Otherwise, undefined. -
__AVX__
Defined as 1 when the/arch:AVX
,/arch:AVX2
, or/arch:AVX512
compiler options are set and the compiler target is x86 or x64. Otherwise, undefined. -
__AVX2__
Defined as 1 when the/arch:AVX2
or/arch:AVX512
compiler option is set and the compiler target is x86 or x64. Otherwise, undefined. -
__AVX512BW__
Defined as 1 when the/arch:AVX512
compiler option is set and the compiler target is x86 or x64. Otherwise, undefined. -
__AVX512CD__
Defined as 1 when the/arch:AVX512
compiler option is set and the compiler target is x86 or x64. Otherwise, undefined. -
__AVX512DQ__
Defined as 1 when the/arch:AVX512
compiler option is set and the compiler target is x86 or x64. Otherwise, undefined. -
__AVX512F__
Defined as 1 when the/arch:AVX512
compiler option is set and the compiler target is x86 or x64. Otherwise, undefined. -
__AVX512VL__
Defined as 1 when the/arch:AVX512
compiler option is set and the compiler target is x86 or x64. Otherwise, undefined. -
_CHAR_UNSIGNED
Defined as 1 if the defaultchar
type is unsigned. This value is defined when the/J
(Default char type is unsigned) compiler option is set. Otherwise, undefined. -
__CLR_VER
Defined as an integer literal that represents the version of the Common Language Runtime (CLR) used to compile the app. The value is encoded in the formMmmbbbbb
, whereM
is the major version of the runtime,mm
is the minor version of the runtime, andbbbbb
is the build number.__CLR_VER
is defined if the/clr
compiler option is set. Otherwise, undefined.// clr_ver.cpp // compile with: /clr using namespace System; int main() { Console::WriteLine(__CLR_VER); }
-
_CONTROL_FLOW_GUARD
Defined as 1 when the/guard:cf
(Enable Control Flow Guard) compiler option is set. Otherwise, undefined. -
__COUNTER__
Expands to an integer literal that starts at 0. The value increments by 1 every time it's used in a source file, or in included headers of the source file.__COUNTER__
remembers its state when you use precompiled headers. This macro is always defined.This example uses
__COUNTER__
to assign unique identifiers to three different objects of the same type. TheexampleClass
constructor takes an integer as a parameter. Inmain
, the application declares three objects of typeexampleClass
, using__COUNTER__
as the unique identifier parameter:// macro__COUNTER__.cpp // Demonstration of __COUNTER__, assigns unique identifiers to // different objects of the same type. // Compile by using: cl /EHsc /W4 macro__COUNTER__.cpp #include <stdio.h> class exampleClass { int m_nID; public: // initialize object with a read-only unique ID exampleClass(int nID) : m_nID(nID) {} int GetID(void) { return m_nID; } }; int main() { // __COUNTER__ is initially defined as 0 exampleClass e1(__COUNTER__); // On the second reference, __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_cli
Defined as the integer literal value 200406 when compiled as C++ and a/clr
compiler option is set. Otherwise, undefined. When defined,__cplusplus_cli
is in effect throughout the translation unit.// cplusplus_cli.cpp // compile by using /clr #include "stdio.h" int main() { #ifdef __cplusplus_cli printf("%d\n", __cplusplus_cli); #else printf("not defined\n"); #endif }
-
__cplusplus_winrt
Defined as the integer literal value 201009 when compiled as C++ and the/ZW
(Windows Runtime Compilation) compiler option is set. Otherwise, undefined. -
_CPPRTTI
Defined as 1 if the/GR
(Enable Run-Time Type Information) compiler option is set. Otherwise, undefined. -
_CPPUNWIND
Defined as 1 if one or more of the/GX
(Enable Exception Handling),/clr
(Common Language Runtime Compilation), or/EH
(Exception Handling Model) compiler options are set. Otherwise, undefined. -
_DEBUG
Defined as 1 when the/LDd
,/MDd
, or/MTd
compiler option is set. Otherwise, undefined. -
_DLL
Defined as 1 when the/MD
or/MDd
(Multithreaded DLL) compiler option is set. Otherwise, undefined. -
__FUNCDNAME__
Defined as a string literal that contains the decorated name of the enclosing function. The macro is defined only within a function. The__FUNCDNAME__
macro isn't expanded if you use the/EP
or/P
compiler option.This example uses the
__FUNCDNAME__
,__FUNCSIG__
, and__FUNCTION__
macros to display function information.[!code-cppNVC_Predefined_Macros_Examples#1]
-
__FUNCSIG__
Defined as a string literal that contains the signature of the enclosing function. The macro is defined only within a function. The__FUNCSIG__
macro isn't expanded if you use the/EP
or/P
compiler option. When compiled for a 64-bit target, the calling convention is__cdecl
by default. For an example of usage, see the__FUNCDNAME__
macro. -
__FUNCTION__
Defined as a string literal that contains the undecorated name of the enclosing function. The macro is defined only within a function. The__FUNCTION__
macro isn't expanded if you use the/EP
or/P
compiler option. For an example of usage, see the__FUNCDNAME__
macro. -
_INTEGRAL_MAX_BITS
Defined as the integer literal value 64, the maximum size (in bits) for a non-vector integral type. This macro is always defined.// integral_max_bits.cpp #include <stdio.h> int main() { printf("%d\n", _INTEGRAL_MAX_BITS); }
-
__INTELLISENSE__
Defined as 1 during an IntelliSense compiler pass in the Visual Studio IDE. Otherwise, undefined. You can use this macro to guard code the IntelliSense compiler doesn't understand, or use it to toggle between the build and IntelliSense compiler. For more information, see Troubleshooting Tips for IntelliSense Slowness. -
_ISO_VOLATILE
Defined as 1 if the/volatile:iso
compiler option is set. Otherwise, undefined. -
_KERNEL_MODE
Defined as 1 if the/kernel
(Create Kernel Mode Binary) compiler option is set. Otherwise, undefined. -
_M_AMD64
Defined as the integer literal value 100 for compilations that target x64 processors or ARM64EC. Otherwise, undefined. -
_M_ARM
Defined as the integer literal value 7 for compilations that target ARM processors. Undefined for ARM64, ARM64EC, and other targets. -
_M_ARM_ARMV7VE
Defined as 1 when the/arch:ARMv7VE
compiler option is set for compilations that target ARM processors. Otherwise, undefined. -
_M_ARM_FP
Defined as an integer literal value that indicates which/arch
compiler option was set for ARM processor targets. Otherwise, undefined.-
A value in the range 30-39 if no
/arch
ARM option was specified, indicating the default architecture for ARM was set (VFPv3
). -
A value in the range 40-49 if
/arch:VFPv4
was set. -
For more information, see
/arch
(ARM).
-
-
_M_ARM64
Defined as 1 for compilations that target ARM64. Otherwise, undefined. -
_M_ARM64EC
Defined as 1 for compilations that target ARM64EC. Otherwise, undefined. -
_M_CEE
Defined as 001 if any/clr
(Common Language Runtime Compilation) compiler option is set. Otherwise, undefined. -
_M_CEE_PURE
Deprecated beginning in Visual Studio 2015. Defined as 001 if the/clr:pure
compiler option is set. Otherwise, undefined. -
_M_CEE_SAFE
Deprecated beginning in Visual Studio 2015. Defined as 001 if the/clr:safe
compiler option is set. Otherwise, undefined. -
_M_FP_CONTRACT
Available beginning in Visual Studio 2022. Defined as 1 if the/fp:contract
or/fp:fast
compiler option is set. Otherwise, undefined. -
_M_FP_EXCEPT
Defined as 1 if the/fp:except
or/fp:strict
compiler option is set. Otherwise, undefined. -
_M_FP_FAST
Defined as 1 if the/fp:fast
compiler option is set. Otherwise, undefined. -
_M_FP_PRECISE
Defined as 1 if the/fp:precise
compiler option is set. Otherwise, undefined. -
_M_FP_STRICT
Defined as 1 if the/fp:strict
compiler option is set. Otherwise, undefined. -
_M_IX86
Defined as the integer literal value 600 for compilations that target x86 processors. This macro isn't defined for x64 or ARM compilation targets. -
_M_IX86_FP
Defined as an integer literal value that indicates the/arch
compiler option that was set, or the default. This macro is always defined when the compilation target is an x86 processor. Otherwise, undefined. When defined, the value is:-
0 if the
/arch:IA32
compiler option was set. -
1 if the
/arch:SSE
compiler option was set. -
2 if the
/arch:SSE2
,/arch:AVX
,/arch:AVX2
, or/arch:AVX512
compiler option was set. This value is the default if an/arch
compiler option wasn't specified. When/arch:AVX
is specified, the macro__AVX__
is also defined. When/arch:AVX2
is specified, both__AVX__
and__AVX2__
are also defined. When/arch:AVX512
is specified,__AVX__
,__AVX2__
,__AVX512BW__
,__AVX512CD__
,__AVX512DQ__
,__AVX512F__
, and__AVX512VL__
are also defined. -
For more information, see
/arch
(x86).
-
-
_M_X64
Defined as the integer literal value 100 for compilations that target x64 processors or ARM64EC. Otherwise, undefined. -
_MANAGED
Defined as 1 when the/clr
compiler option is set. Otherwise, undefined. -
_MSC_BUILD
Defined as an integer literal that contains the revision number element of the compiler's version number. The revision number is the last element of the period-delimited version number. For example, if the version number of the Microsoft C/C++ compiler is 15.00.20706.01, the_MSC_BUILD
macro is 1. This macro is always defined. -
_MSC_EXTENSIONS
Defined as 1 if the on-by-default/Ze
(Enable Language Extensions) compiler option is set. Otherwise, undefined. -
_MSC_FULL_VER
Defined as an integer literal that encodes the major, minor, and build number elements of the compiler's version number. The major number is the first element of the period-delimited version number, the minor number is the second element, and the build number is the third element.For example, if the Microsoft C/C++ compiler version is 19.39.33519,
_MSC_FULL_VER
is 193933519. Entercl /?
at the command line to view the compiler's version number. This macro is always defined. For more information about compiler versioning, see C++ compiler versioning and specifically Service releases starting with Visual Studio 2017 for more information about Visual Studio 2019 16.8, 16.9, 16.10 and 16.11, which require_MSC_FULL_VER
to tell them apart. -
_MSC_VER
Defined as an integer literal that encodes the major and minor number elements of the compiler's version number. The major number is the first element of the period-delimited version number and the minor number is the second element. For example, if the version number of the Microsoft C/C++ compiler is 17.00.51106.1, the value of_MSC_VER
is 1700. Entercl /?
at the command line to view the compiler's version number. This macro is always defined.To test for compiler releases or updates in a given version of Visual Studio or later, use the
>=
operator. You can use it in a conditional directive to compare_MSC_VER
against that known version. If you have several mutually exclusive versions to compare, order your comparisons in descending order of version number. For example, this code checks for compilers released in Visual Studio 2017 and later. Next, it checks for compilers released in or after Visual Studio 2015. Then it checks for all compilers released before Visual Studio 2015:#if _MSC_VER >= 1910 // . . . #elif _MSC_VER >= 1900 // . . . #else // . . . #endif
For more information about Visual Studio 2019 16.8 and 16.9, and 16.10 and 16.11, which share the same major and minor versions (and so have the same value for
_MSC_VER
), see Service releases starting with Visual Studio 2017.For more information about the history of compiler versioning, and compiler version numbers and the Visual Studio versions they correspond to, see C++ compiler versioning. Also, Visual C++ Compiler Version on the Microsoft C++ team blog.
-
_MSVC_LANG
Defined as an integer literal that specifies the C++ language standard targeted by the compiler. Only code compiled as C++ sets it. The macro is the integer literal value201402L
by default, or when the/std:c++14
compiler option is specified. The macro is set to201703L
if the/std:c++17
compiler option is specified. The macro is set to202002L
if the/std:c++20
compiler option is specified. It's set to a higher, unspecified value when the/std:c++latest
option is specified. Otherwise, the macro is undefined. The_MSVC_LANG
macro and/std
(Specify language standard version) compiler options are available beginning in Visual Studio 2015 Update 3. -
__MSVC_RUNTIME_CHECKS
Defined as 1 when one of the/RTC
compiler options is set. Otherwise, undefined. -
_MSVC_TRADITIONAL
:- Available beginning with Visual Studio 2017 version 15.8: Defined as 0 when the preprocessor conformance mode
/experimental:preprocessor
compiler option is set. Defined as 1 by default, or when the/experimental:preprocessor-
compiler option is set, to indicate the traditional preprocessor is in use. - Available beginning with Visual Studio 2019 version 16.5: Defined as 0 when the preprocessor conformance mode
/Zc:preprocessor
compiler option is set. Defined as 1 by default, or when the/Zc:preprocessor-
compiler option is set, to indicate the traditional preprocessor is in use (essentially,/Zc:preprocessor
replaces the deprecated/experimental:preprocessor
).
#if !defined(_MSVC_TRADITIONAL) || _MSVC_TRADITIONAL // Logic using the traditional preprocessor #else // Logic using cross-platform compatible preprocessor #endif
- Available beginning with Visual Studio 2017 version 15.8: Defined as 0 when the preprocessor conformance mode
-
_MT
Defined as 1 when/MD
or/MDd
(Multithreaded DLL) or/MT
or/MTd
(Multithreaded) is specified. Otherwise, undefined. -
_NATIVE_WCHAR_T_DEFINED
Defined as 1 when the/Zc:wchar_t
compiler option is set. Otherwise, undefined. -
_OPENMP
Defined as integer literal 200203, if the/openmp
(Enable OpenMP 2.0 Support) compiler option is set. This value represents the date of the OpenMP specification implemented by MSVC. Otherwise, undefined.// _OPENMP_dir.cpp // compile with: /openmp #include <stdio.h> int main() { printf("%d\n", _OPENMP); }
-
_PREFAST_
Defined as 1 when the/analyze
compiler option is set. Otherwise, undefined. -
__SANITIZE_ADDRESS__
Available beginning with Visual Studio 2019 version 16.9. Defined as 1 when the/fsanitize=address
compiler option is set. Otherwise, undefined. -
__TIMESTAMP__
Defined as a string literal that contains the date and time of the last modification of the current source file, in the abbreviated, constant length form returned by the CRTasctime
function, for example,Fri 19 Aug 13:32:58 2016
. This macro is always defined. -
_VC_NODEFAULTLIB
Defined as 1 when the/Zl
(Omit Default Library Name) compiler option is set. Otherwise, undefined. -
_WCHAR_T_DEFINED
Defined as 1 when the default/Zc:wchar_t
compiler option is set. The_WCHAR_T_DEFINED
macro is defined but has no value if the/Zc:wchar_t-
compiler option is set, andwchar_t
is defined in a system header file included in your project. Otherwise, undefined. -
_WIN32
Defined as 1 when the compilation target is 32-bit ARM, 64-bit ARM, x86, or x64. Otherwise, undefined. -
_WIN64
Defined as 1 when the compilation target is 64-bit ARM or x64. Otherwise, undefined. -
_WINRT_DLL
Defined as 1 when compiled as C++ and both/ZW
(Windows Runtime Compilation) and/LD
or/LDd
compiler options are set. Otherwise, undefined.
No preprocessor macros that identify the ATL or MFC library version are predefined by the compiler. ATL and MFC library headers define these version macros internally. They're undefined in preprocessor directives made before the required header is included.
-
_ATL_VER
Defined in<atldef.h>
as an integer literal that encodes the ATL version number. -
_MFC_VER
Defined in<afxver_.h>
as an integer literal that encodes the MFC version number.
Macros (C/C++)
Preprocessor operators
Preprocessor directives