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...

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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.

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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.