Would it be technically possible to create a "fat"/"Universal" Windows DLL?

Not withstanding that there is currently no tool that can create one, is it possible to have put both x64 and x86 symbols into a DLL, and have it work on both x64 and x86?

Creating one would be possible if开发者_高级运维 there is some sort of specification/hack that would allow the Windows DLL loader to skip over incompatible symbols etc...

No, a DLL contains only one header, IMAGE_FILE_HEADER in the SDK. Which contains the Machine field, it indicates what kind of code the DLL contains. There's no way to specify more than one machine type.

Files on an NTFS filesystem are perfectly capable of containing multiple PE binaries, using NTFS alternate data streams. However, a google search suggests that attempts to use LoadLibrary with streams have met with failure.