You have several problems.
extern(C++) only specifies the calling convention, not the visibility
of the symbol. To export the symbol, list it in a .def file or mark
the function with export in the module itself, ala:
export extern(C++) void SetInt(int * foo) {}
I don't know why, but if you use a .def file instead of `export` the
function will be exported as a C function with no name mangling.
Anyway, use a .def file like the one below and pass it to DMD while
compiling the DLL, and it should be exported with that name (and
change the string "mydll.dll" of course):
LIBRARY "mydll.dll"
DESCRIPTION 'My DLL written in D'
EXETYPE NT
SUBSYSTEM WINDOWS
CODE PRELOAD DISCARDABLE
DATA WRITE
EXPORTS
SetInt
ATA.lib is probably the autogenerated import library which is useful
for implicit linking.
