Calling convention)

There are a variety of function call conventions. Here we will briefly talk about: 1. the _ stdcall call convention is equivalent to the Pascal call convention that is frequently used in 16-bit dynamic libraries. In 32-bit VC ++ 5.0, Pascal's call Convention is no longer supported (in fact, it has been defined as _ stdcall. In addition to _ Pascal, __fortran and _ syscall are not supported). Instead, they are replaced by the _ stdcall call convention. The two are essentially the same, that is, the function parameter is passed from right to left through the stack. The called function clears the memory stack of the transfer parameter before returning, but the difference is the modifier of the function name. _ Stdcall is the default calling method of the PASCAL program. It is usually used in Win32 API. The function uses the stack pressure method from right to left and clears the stack when it exits. After compiling a function, VC adds an underline prefix to the function name, and adds "@" and the number of bytes of the parameter to the function name. (_ Functionname @ number)
2. c call conventions (which are described by the _ cdecl keyword) are pushed to the stack in sequence from right to left. The caller pushes the parameters to the stack. The memory stack of the transmitted parameters is maintained by the caller (because of this, the function that implements variable parameters can only use variable parameters such as printf ). In addition, the function name modification conventions are also different. _ Cdecl is the default call Method for C and C ++ programs. Every function that calls it contains the code to clear the stack. Therefore, the size of the executable file generated is larger than that of the call to the _ stdcall function. The function uses the stack pressure mode from right to left. After compiling a function, VC adds an underline prefix to the function name. (_ Functionname) is the default MFC call convention. 3. The _ fastcall call convention is "people" as its name. Its main feature is fast because it transmits parameters through registers (in fact, it uses ECx and EDX to transmit the first two DWORD or smaller parameters, and the remaining parameters are still transmitted from the right to the left pressure stack, the called function clears the memory stack of the transfer parameter before returning). In terms of the function name modification conventions, it is different from the previous two. _ Fastcall functions use registers to pass parameters. After compiling a function, VC adds the "@" prefix to the function name, and adds "@" and the number of parameters after the function name. (@ Functionname @ number) 4. thiscall is only applied to "C ++" member functions. This pointer is stored in the Cx register and the parameter is pressed from right to left. Thiscall is not a keyword and cannot be specified by programmers. 5. Naked call uses 1-4 call timing. If necessary, the compiler will generate code to save the ESI, EDI, EBX, and EBP registers when entering the function, when you exit the function, the code is generated to restore the content of these registers. Naked call does not generate such code. The naked call is not a type modifier, so it must be used together with _ declspec. The keywords _ stdcall, _ cdecl, and _ fastcall can be directly added before the function to be output, or in the setting environment... select/C ++/code generation. When the keywords added before the output function are different from those selected in the compiling environment, the keywords directly added before the output function are valid. Their corresponding command line parameters are/GZ,/GD, And/GR. The default status is/GD, Which is _ cdecl. To fully imitate Pascal's call convention, you must first use the _ stdcall call Convention. As for the function name Modification Convention, you can use other methods to imitate it. Another thing worth mentioning is winapi macro, windows. h supports this macro. It can translate the function into an appropriate call convention. In Win32, it is defined as _ stdcall. You can use the winapi macro to create your own APIs. # Define callback _ stdcall # define winapi _ stdcall