What are the function calling conventions in C++?

Calling conventions in C define how function arguments are passed and values ​​are returned, including cdecl, fastcall, thiscall, and stdcall. In practice, the stdcall calling convention can be used to load and call functions in a DLL.

C Function Calling Convention

In C, the calling convention defines how arguments to a function are passed and returned. Different calling conventions have different trade-offs in terms of performance, memory usage, and code portability.

Common calling conventions

• cdecl (also known as stdcall): Applicable to Windows and Linux, parameters are pushed from right to left Stack, pop from left to right.
• fastcall: Only used in Windows, the first two parameters are passed through registers, and the other parameters are pushed onto the stack.
• thiscall: Used in object-oriented programming for member functions, the this pointer is passed through a register as the first parameter.
• stdcall: Similar to cdecl, but uses Windows-style name decoration.

Practical case

The following C code demonstrates the use of stdcall to call a function:

#include <windows.h> // 只适用于 Windows

typedef void (WINAPI *pfnPrintString)(const char*);

int main()
{
    // 加载 DLL 并获取函数指针
    HMODULE hDll = LoadLibrary("mydll.dll");
    pfnPrintString PrintString = (pfnPrintString)GetProcAddress(hDll, "PrintString");

    // 调用函数，传递参数
    PrintString("Hello, world!");

    // 卸载 DLL
    FreeLibrary(hDll);

    return 0;
}

In this example, stdcall is used to call The convention is to load and call the PrintString function from the DLL.

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