[zz]MFC - __fastcall

[zz]MFC - __fastcall

Microsoft Specific

The __fastcall calling convention specifies that arguments to functions are to be passed in registers, when possible. The following list shows the implementation of this calling convention.

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	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.

Note   Future compiler versions may use different registers to store parameters.

Using the /Gr compiler option causes each function in the module to compile as fastcall unless the function is declared with a conflicting attribute, or the name of the function is main.

Example

In the following example, the function named DeleteAggrWrapper is passed arguments in registers:

//  Example of the __fastcall keyword
#define  FASTCALL    __fastcall
   
void  FASTCALL DeleteAggrWrapper( void *  pWrapper);
//  Example of the __ fastcall keyword on function pointer
typedef BOOL (__fastcall  * funcname_ptr)( void   *  arg1,  const   char   *  arg2, DWORD flags, );