_ Stdcall, _ cdecl, _ fastcall

(1) _ stdcall call _ stdcall is the default call method of the PASCAL program. The parameter uses the pressure stack method from right to left. The called function itself clears the stack before returning. Win32 APIs use the _ stdcall call method. This macro definition illustrates the problem: # define winapi _ stdcall is compiled in C mode, and _ stdcall is called by an underscore before the output function name, add the "@" symbol and the number of bytes of the parameter, for example, _ functionname @ number.

(2) _ cdecl call _ cdecl is the default call method of C/C ++. The parameter uses the pressure stack mode from right to left, and the memory stack of the transfer parameter is maintained by the caller. _ Functions agreed by cedcl can only be called by C/C ++. Each function that calls it contains code for clearing the stack, therefore, the size of the executable file is larger than that of the _ stdcall function. Since the parameter memory stack of the _ cdecl call method is maintained by the caller, the variable-length parameter function can (or can only) use this call convention. Because visual c ++ uses the _ cdecl call method by default, _ stdcall should be used to call DLL in VC. According to the C compilation method, the _ cdecl call Convention only underlines the output function name, such as _ functionname.

(3) _ fastcall: The _ fastcall call is faster. It passes parameters through the internal registers of the CPU. (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), and adds the "@" symbol before the output function name according to the C compilation method and the _ fastcall call convention, add the "@" symbol and the number of bytes of the parameter, for example, @ 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.

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.

2) Name modification conventions

1. decoration name)

The "C" or "C ++" functions are identified by modifier internally (Compilation and link. Modifier is a string generated by the compiler when compiling a function definition or prototype. In some cases, modifying the name of a function is necessary, for example, specifying the output "C ++" overload function, constructor, and destructor in the module definition file, for example, call the "C" or "C ++" function in the assembly code.

Modifier names are jointly determined by function names, class names, call conventions, return types, parameters, and so on.

2. The name Modification Convention varies with the call convention and the compilation type (C or C ++. The function name modification conventions vary with the compilation type and call conventions.

Rules for modifying function names during a and c Compilation:

The _ stdcall call Convention adds an underline prefix before the output function name, followed by the "@" symbol and the number of bytes of the parameter. The format is _ functionname @ number.

The _ cdecl call Convention only adds an underline prefix before the output function name in the format of _ functionname.

_ Fastcall: add the "@" symbol before the output function name, followed by the "@" symbol and the number of bytes of the parameter. The format is @ functionname @ number.

They do not change the case sensitivity of the output function name. This is different from Pascal's call conventions. Pascal's output function names are not modified and all are capitalized.

B. Conventions for function name modification during C ++ Compilation:

_ Stdcall call conventions:
1. Take "?" Start of the function name, followed by the function name;
2. The parameter table starts with "@ YG" after the function name, followed by the parameter table;
3. The parameter table is represented in code:
X -- void,
D -- char,
E -- unsigned char,
F -- short,
H -- int,
I -- unsigned int,
J -- long,
K -- unsigned long,
M -- float,
N -- double,
_ N -- bool,
....
Pa -- indicates the pointer. The code behind the pointer indicates the pointer type. If a pointer of the same type appears consecutively, it is replaced by "0". A "0" indicates a repetition;
4. the first item of the parameter table is the type of the return value of the function, followed by the Data Type of the parameter. the pointer ID is prior to the Data Type indicated by the parameter;
5. mark the end of the entire name with "@ Z" after the parameter table. If this function has no parameter, it ends with "Z.

The format is "? Functionname @ YG ***** @ Z "or"? Functionname @ YG * xz ", for example
Int test1 (char * var1, unsigned long) ----- "? Test1 @ yghpadk @ Z"
Void Test2 () ----- "? Test2 @ ygxxz"

_ Cdecl:
The rules are the same as the _ stdcall call Convention above, except that the start mark of the parameter table is changed from "@ YG" to "@ ya ".

_ Fastcall:
The rules are the same as the _ stdcall call Convention above, but the start mark of the parameter table is changed from "@ YG" to "@ Yi ".

The "_ cedcl" Declaration for the function can only be called by C/C ++.

CB uses four modifiers for output function declaration.
// _ Cdecl
The default value of CB. It will add _ before the output function name and keep this function name unchanged. parameters are passed to the stack in sequence from right to left, it can also be written as _ cdecl and cdecl.
// _ Fastcall
The parameters of the function modified by her will be processed by registers with the intention of adding @ before the function name, and the parameters will be pushed to the stack in the order from left to right;
// _ Pascal
It indicates that the function name uses the naming convention in Pascal format. In this case, all function names are capitalized. The parameters are pressed from left to right;
// _ Stdcall
Use the standard function name. The function name will not change. When _ stdcall is used. The parameter can be set to _ stdcall in the order from right to left;