如何从用C / C ++编写的DLL调用导出的函数，其返回类型为char *或string？

Question

We designed C/C++ DLL just like this:

WIN32_DLL_EXPORT int FnRetInt(int i)
{
   ....
   return 32 ;
} 

WIN32_DLL_EXPORT char* FnRetString()
{
   return "THIS IS A TEST STRING" ;
}

when we invoke these two functions in Go by using syscall:

hd:=syscall.NewLazyDLL(dll_path)
proc:=hd.NewProc(dll_func_name)
ret:=proc.Call()

we found:

FnRetInt worked ok, but FnRetString didn't. proc.Call return type is uintptr, how can we change it to the type we wanted (for exsample: char* or string)?

Answer 1

A uintptr is a Go type that represents a pointer. You can use the unsafe package and convert it to unsafe.Pointer, and then you can convert an unsafe.Pointer into any Go pointer type. So you could do something like

str := (*uint8)(unsafe.Pointer(ret))

to get a *uint8 back.