_ Stdcall conventions

_ Stdcall conventions

If a DLL written in VC ++ is to be called by a program written in other languages, the function call method should be declared as _ stdcall. winapi adopts this method, the default call method of C/C ++ is _ cdecl. The _ stdcall method is different from the _ cdecl method for generating symbols for function names. If the C compilation method is used (the function must be declared as extern "C" in C ++), __stdcall indicates that the name of the output function must be underlined, the symbol "@" is followed by the number of bytes of the parameter, in the form of _ functionname @ number. The call Convention of _ cdecl is to only underline the name of the output function, in the form of _ functionname.

In Windows programming, macros of common function types are related to _ stdcall and _ cdecl (Excerpted from windef. h ):

# Define callback _ stdcall // This is the legendary callback function.

# Define winapi _ stdcall // This is the legendary winapi

# Define winapiv _ cdecl

# Define apientry winapi // The dllmain entry is here

# Define apiprivate _ stdcall

# Define Pascal _ stdcall

In Lib. H, the Add function should be declared as follows:

Int _ stdcall add (int x, int y );

In the Application project, the function pointer type should be defined:

Typedef int (_ stdcall * lpaddfun) (INT, INT );

In Lib. h declares the function as _ stdcall, while typedef int (* lpaddfun) (INT, INT) is still used in the application project. An error will occur during runtime (because the type does not match, in the Application project, it is still the default _ cdecl call). The Dialog Box 7 is displayed.

Figure 7 running errors when the call conventions do not match

The section in Figure 8 actually shows the cause of the error, that is, "this is usually a result ...".

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