调用方式(VC/MFC)

                 C/C++ 调用方式

(1) __cdecl

This is the default calling convention for C and C++ programs. Because the stack is cleaned up by the caller, it can do vararg functions. The __cdecl calling convention creates larger executables than , because it requires each function call to include stack cleanup code. The following list shows the implementation of this calling convention.

Element	Implementation
Argument-passing order	Right to left
Stack-maintenance responsibility	Calling function pops the arguments from the stack
Name-decoration convention	Underscore character (_) is prefixed to names
Case-translation convention	No case translation performed

Place the __cdecl modifier before a variable or a function name. Because the C naming and calling conventions are the default, the only time you need to use __cdecl is when you have specified the /Gz (stdcall) or /Gr (fastcall) compiler option. The compiler option forces the __cdecl calling convention

 (2) __stdcall

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.

Element	Implementation
Argument-passing order	Right to left.
Argument-passing convention	By value, unless a pointer or reference type is passed.
Stack-maintenance responsibility	Called function pops its own arguments from the stack.
Name-decoration convention	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
Case-translation convention	None

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

(3) __fastcall

The __fastcall calling convention specifies that arguments to functions are to be passed in registers, when possible. The following list shows the implementation of this calling convention.

Element	Implementation
Argument-passing order	The first two DWORD or smaller arguments are passed in ECX and EDX registers; all other arguments are passed right to left.
Stack-maintenance responsibility	Called function pops the arguments from the stack.
Name-decoration convention	At sign (@) is prefixed to names; an at sign followed by the number of bytes (in decimal) in the parameter list is suffixed to names.
Case-translation convention	No case translation performed.

Note   Future compiler versions may use different registers to store parameters.

Using the compiler option causes each function in the module to compile as fastcall unless the function is declared with a conflicting attribute, or the name of the function is main.