Compile unmanaged executable for BOTH x86 and x64

Question

Is there any way to compile an EXE file, so that it will run natively in both x86 and x64? Something like: compile both codebases and pack them into a single executable.

I know .NET code could run in "any cpu" mode, but it is not what I want.

Answer 1

A 32-bit executable will run natively on 32-bit and x64 Windows machines. The only way you're going to get x64 execution within a 32-bit PE file is by using an undocumented gate, which I highly doubt anyone uses in practice because it's highly version dependent (and undocumented).

Then again you make it so the 32-bit binary will execute a 64-bit version of the binary and exit if it detects a 64-bit CPU...

Answer 2

You could take the Process Explorer approach. In your 32-bit binary embed the 64-bit binary as a resource. If the 32-bit binary is launched on a 64-bit machine, extract the 64-bit binary and launch that.