The topic you requested is included in another documentation set. For convenience, it's displayed below. Choose Switch to see the topic in its original location.



The latest version of this topic can be found at __stdcall.

Microsoft Specific**

The __stdcall calling convention is used to call Win32 API functions. The callee cleans the stack, so the compiler makes vararg functions __cdecl. Functions that use this calling convention require a function prototype.

return-type __stdcall function-name[(argument-list)]  

The following list shows the implementation of this calling convention.

Argument-passing orderRight to left.
Argument-passing conventionBy value, unless a pointer or reference type is passed.
Stack-maintenance responsibilityCalled function pops its own arguments from the stack.
Name-decoration conventionAn underscore (_) is prefixed to the name. The name is followed by the at sign (@) followed by the number of bytes (in decimal) in the argument list. Therefore, the function declared as int func( int a, double b ) is decorated as follows: _func@12
Case-translation conventionNone

The /Gz compiler option specifies __stdcall for all functions not explicitly declared with a different calling convention.

Functions declared using the __stdcall modifier return values the same way as functions declared using __cdecl.

On ARM and x64 processors, __stdcall is accepted and ignored by the compiler; on ARM and x64 architectures, by convention, arguments are passed in registers when possible, and subsequent arguments are passed on the stack.

For non-static class functions, if the function is defined out-of-line, the calling convention modifier does not have to be specified on the out-of-line definition. That is, for class non-static member methods, the calling convention specified during declaration is assumed at the point of definition. Given this class definition,

struct CMyClass {  
   void __stdcall mymethod();  


void CMyClass::mymethod() { return; }  

is equivalent to this

void __stdcall CMyClass::mymethod() { return; }  

In the following example, use of __stdcall results in all WINAPI function types being handled as a standard call:

// Example of the __stdcall keyword  
#define WINAPI __stdcall  
// Example of the __stdcall keyword on function pointer  
typedef BOOL (__stdcall *funcname_ptr)(void * arg1, const char * arg2, DWORD flags, ...);  

Argument Passing and Naming Conventions