You can export C functions in three ways:
__declspec(dllexport)
declaration in the C file.
In this case you should also make the functions use the
cdecl
calling convention, which removes another level of name mangling.
/export
directive in the link command.
.def
file.
An example of method 3 follows. Let us assume you have the following C code in a file called
example.c
.
int _stdcall MultiplyMain(void *hinstDll,unsigned long
dwReason,void *reserved)
{
return(1);
}
int multiply (int i1, int i2)
{ int result;
result = i1 * i2 * 500;
return result;
}
Then you can create a DLL by, for example, using a 32 bit C compiler such as lcc.
lcc -O -g2 example.c
lcclnk.exe -dll -entry MultiplyMain example.obj
example.def -subsystem
windows
You now need to create a
multiply.def
file that contains the following line
exports multiply=multiply
to export the function
multiply
as the symbol
multiply
. If you only include the line "
exports multiply
" then the name of the external symbol is likely to be "
_multiply
" or "
_multiply@8
" depending on whether the function is compiled as
__cdecl
or
__stdcall
. The addition of the "
= multiply
" overrides the internal function name with the new name.
If you run Windows then you can view the list of exported symbols from a given DLL by selecting the DLL from an explorer, then right clicking on it and selecting QuickView. This brings up some text about the DLL.
Finally, you should use the LispWorks FLI to define your C function in your Lisp code. This definition should look something like:
(fli:define-foreign-function (multiply "multiply")
((x :int)
(y :int))
:result-type int
:module :my-dll
:calling-convention :cdecl)
Note that the
define-foreign-function
also includes a
:calling-convention
keyword to specify that the function we are interfacing to is defined as using the
__cdecl
calling convention.