How can a DLL have zero exports?

Question

I recently ran across a DLL installed on my system that Dependancy Walker (and every other utility I tried) says has zero exports by name or ordinal, yet the file is approximately 4mb in size. I thought the sole purpose of a DLL was to export functions for use by other code so what would be the purpose of a dll with no visible exports?

Answer 1

One way to think of a DLL is as a container for functions. Exporting a function from a DLL makes those functions visible to callers outside of the DLL. While exporting functions from a DLL is perhaps the most common way to provide access to them, many platforms provide other ways to access functions which have not been exported such as reflection in the .NET Framework and Java and (I think) LoadLibtary / GetProcAddress in Win32

Reasons for doing this are varied, often it is because it is beneficial to the developer to have functions in a library but undesirable for those functions to be called from external applications

Answer 2

Resource-only DLL, maybe? Those are used quite often for localization purposes, for example.

EDIT: it's also possible to have a DLL with code that does something in DllMain() to somehow make its functionality available. The DLL can register itself with some global dispatcher, for example, or create named kernel objects...