I am getting this linker error.
mfcs80.lib(dllmodul.obj) : error LNK2005: _DllMain@12 already defined in MSVCRT.lib(dllmain.obj)
This can also occur if your solution has multiple projects that export the same symbols. For example if you have sub-project that builds foo.dll with a foo.def file that exports DoFoo and a sub-project for bar.dll with a bar.def file that exports DoFoo, a collision will occur and this is the error you will see when you link.