Skip to content

Latest commit

 

History

History
74 lines (53 loc) · 3 KB

w64.md

File metadata and controls

74 lines (53 loc) · 3 KB
title ms.custom ms.date ms.technology ms.topic f1_keywords dev_langs helpviewer_keywords ms.assetid author ms.author ms.workload
__w64 | Microsoft Docs
11/04/2016
cpp-language
language-reference
__w64_cpp
C++
__w64 keyword [C++]
64-bit compiler [C++], __w64 keyword
Win64 [C++], __w64 keyword
b9d0c820-e132-40bc-b532-56edca132a6c
mikeblome
mblome
cplusplus

__w64

Microsoft Specific

This keyword is obsolete. In versions of Visual Studio earlier than Visual Studio 2013, this lets you mark variables, so that when you compile with /Wp64 the compiler will report any warnings that would be reported if you were compiling with a 64-bit compiler.

Syntax

type __w64 identifier

Parameters

type
One of the three types that could cause problems in code being ported from a 32-bit to a 64-bit compiler: int, long, or a pointer.

identifier
The identifier for the variable you are creating.

Remarks

Important

The /Wp64 compiler option and __w64 keyword are deprecated in Visual Studio 2010 and Visual Studio 2013 and removed starting in Visual Studio 2013. If you use the /Wp64 compiler option on the command line, the compiler issues Command-Line Warning D9002. The __w64 keyword is silently ignored. Instead of using this option and keyword to detect 64-bit portability issues, use a Visual C++ compiler that targets a 64-bit platform. For more information, see Configure Visual C++ for 64-bit, x64 targets.

Any typedef that has __w64 on it must be 32 bits on x86 and 64 bits on x64.

To detect portability issues by using versions of the Visual C++ compiler earlier than Visual Studio 2010, the __w64 keyword should be specified on any typedefs that change size between 32 bit and 64 bit platforms. For any such type, __w64 must appear only on the 32-bit definition of the typedef.

The __w64 keyword is ignored if the compilation does not use /Wp64.

For more information about porting to 64-bit, see the following topics:

Example

// __w64.cpp  
// compile with: /W3 /Wp64  
typedef int Int_32;  
#ifdef _WIN64  
typedef __int64 Int_Native;  
#else  
typedef int __w64 Int_Native;  
#endif  
  
int main() {  
   Int_32 i0 = 5;  
   Int_Native i1 = 10;  
   i0 = i1;   // C4244 64-bit int assigned to 32-bit int  
  
   // char __w64 c;  error, cannot use __w64 on char  
}

See also

Keywords