Unused routines still result in huge .EXE

[a740g]

upx unzips the exe and then runs it, if I remember correctly. So, technically, the exe is still the same size. Actually, it's larger. Because you're storing the compressed exe and then upx dumps the uncompressed to a temp folder. So now you're storing 1.5x the size.

That depends on the executable format and the environment. For example, UPX decompresses Linux ELF and Windows PE/COFF executables directly to the RAM. In most cases, UPX compressed executables can run without issues in a read-only and limited storage environment.

However, there are some quirks that users should be aware of on certain platforms - https://github.com/upx/upx/blob/devel/doc/upx-doc.txt