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.
The following list shows the implementation of this calling convention.
Right to left.
By value, unless a pointer or reference type is passed.
Called function pops its own arguments from the stack.
An 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
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,
is equivalent to this
In the following example, use of __stdcall results in all WINAPI function types being handled as a standard call: