[qwename]

Last year I reversed engineered a (36KiB) Windows PE binary[1] to obtain C++ source code that compiled to almost the exact same bytes. What stumped me was an undocumented section that contained metadata, which I gave up on figuring out.

Assuming you compile with the same options and in the same environment, the machine instructions should be the same.

EDIT: The compiler in question though is whatever Visual Basic 6.0 uses, so I wouldn't call it modern today.

[1] https://github.com/qwename/quirky-protector

[throwaway7767]

One of the longstanding issues the Tor project had with their reproducible builds was that the windows builds, built with Visual Studio, would always have a small piece of data in the same place that differed for each build. It took months to figure it out, but it turned out to be a bug in the MS compiler where they were including some uninitialized memory from the compiler into the resulting binary. IIRC it was fixed after being reported to Microsoft.

Could be the same or similar issue you are facing, given the age of the compiler.

I don't have a reference to link to though, Roger Dingledine told me this in person at a conference when discussing issues related to reproducible builds. But there should be an issue in the tor bug tracker.