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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.

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, );