argument. The dll is in the PATH. I don't understand why it needs the -L argument. I'll figure this out later. If I use -lglasPng.dll (additional .dll) it doesn't work either.
Unix has standard places to install and search for libraries; Windows doesn't, and almost every library that doesn't come with your build system will need at least one -L option to tell the linker where to find it.
As I mentioned in my first message, it looks for multiple file names with -l: first it tries a .dll, then it tries a .lib (static library or import library for older DLLs). It does this mechanically; if you also include the .dll suffix, then it looks for library.dll.dll and library.dll.lib, which is almost certainly wrong.