stdcall,cdecl,fastcall,thiscall

最新推荐文章于 2025-12-10 20:27:30 发布

原创最新推荐文章于 2025-12-10 20:27:30 发布 · 1.3k 阅读

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#function #compiler #underscore #microsoft #translation #c++

本文详细介绍了C++中各种调用约定的实现细节，包括__stdcall、__cdecl、__fastcall和__thiscall等，涵盖了参数传递顺序、堆栈维护责任、名称修饰约定等内容。

从msdn上摘录，__*call的解释

__stdcall

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

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 in C	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 __stdcall calling convention is used to call Win32 API functions.

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

__cdecl

Element	Implementation
Argument-passing order	Right to left
Stack-maintenance responsibility	Calling function pops the arguments from the stack
Name-decoration convention in C	Underscore character (_) is prefixed to names, except when exporting __cdecl functions that use C linkage.
Case-translation convention	No case translation performed

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 __stdcall, because it requires each function call to include stack cleanup code.

The /Gd compiler option forces the __cdecl calling convention.

vararg member functions use the __cdecl calling convention. All function arguments are pushed on the stack, with the this pointer placed on the stack last

__fastcall

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 in C	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.

The __fastcall calling convention specifies that arguments to functions are to be passed in registers, when possible.

Using the /Gr compiler option causes each function in the module to compile as fastcall.

__thiscall

Element	Implementation
Argument-passing order	Arguments are pushed on the stack from right to left, with the this pointer being passed via register ECX, and not on the stack, on the x86 architecture.
Stack-maintenance responsibility	the callee cleans the stack
Name-decoration convention
Case-translation convention

The __thiscall calling convention is used on member functions and is the default calling convention used by C++ member functions that do not use variable arguments.

One reason to use __thiscall is in classes whose member functions use __clrcall by default. In that case, you can use __thiscall to make individual member functions callable from native code.

__clrcall

Specifies that a function can only be called from managed code.

Format of a C++ Decorated Name

A decorated name for a C++ function contains the following information:

l The function name.

l The class that the function is a member of, if it is a member function. This may include the class that encloses the function's class, and so on.

l The namespace the function belongs to (if it is part of a namespace).

l The types of the function's parameters.

l The calling convention.

l The return type of the function.

The function and class names are encoded in the decorated name. The rest of the decorated name is a code that has internal meaning only for the compiler and the linker. The following are examples of undecorated and decorated C++ names.