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Wow, I’m super happy to see folks interested in my little project! I was inspired to do this thanks to a challenge posted to Twitter. It was fun putting togethe

Wow, I’m super happy to see folks interested in my little project! I was inspired to do this thanks to a challenge posted to Twitter. It was fun putting together this binary and learning more than I thought I was going to learn about DOS extenders and the PE format. Happy to answer any questions!

btilly 6y ago
How hard would it be to add support for other operating systems like OS X as well?
- jonny_eh 6y ago
  My guess is that the headers would be incompatible.
- obverse 6y ago
  I've tried going down that rabbit hole before. The primary issue that stopped me was the different executable file formats. I never took it anywhere, but I think the way to go would be a "polyglot" script that could be interpreted by different script engines (sh/bat) that would then pick the correct executable for the given OS. This would require the user to change the file extension as well as download multiple executable files so I don't necessarily like this solution from an elegance stand point.
  - sgtnoodle 6y ago
    I've had good success with shebangs combined with zip archives containing python code. Zip files use a footer rather than a header, and python natively supports executing scripts out of them. The beginning of the file can have a shebang, allowing it to specify the interpreter to use. The only trick is that windows doesn't support shebangs, and so you need to associate your chosen file extension with python on every system. Also, you need python installed obviously. What that gives you is a stable entry point into python code. From there, you can run whatever platform specific code you want.
- nneonneo 6y ago
  Most file formats have a magic number at offset 0. The magic numbers for EXE ("MZ"), OS X (0xfeedface/0xfeedfacf) and Linux ("\x7fELF") are all different, so they aren't compatible.
  - viraptor 6y ago
    Not on windows, but that depends on the OS. On Linux the handlers are pluggable via binfmt (https://en.m.wikipedia.org/wiki/Binfmt_misc https://en.m.wikipedia.org/wiki/Binfmt_misc) and this allows for example wine and .net binaries to work transparently. (I'm not aware of it, but maybe there a similar system in windows)
  - pwdisswordfish4 6y ago
    αcτµαlly pδrταblε εxεcµταblε https://news.ycombinator.com/item?id=24256883 https://news.ycombinator.com/item?id=24256883 https://justine.storage.googleapis.com/ape.html https://justine.storage.googleapis.com/ape.html
  - wizzwizz4 6y ago
    The PE magic number doesn't need to be at offset zero, which is why you can do this. Mach and ELF do need to be at offset zero, so you can't have something that's Mach and ELF at the same time. In theory, this is possible, if you can recover from COM executing the header.
mehrdadn 6y ago
Do you know of a good way (if any) to shrink the size of the DOS header as much as possible on MSVC? (Like to remove the "This program cannot be run in DOS mode" notice, and other things you don't need on Windows.)
- dblohm7 6y ago
  It’s just a MSVC linker directive. Use /STUB
  - mehrdadn 6y ago
    Yeah I tried that at some point but I didn't figure out what to feed it to make a smaller executable that would still run. Not sure what I might've done wrong unfortunately, it's been a few years.

btilly 6y ago

How hard would it be to add support for other operating systems like OS X as well?

jonny_eh 6y ago
My guess is that the headers would be incompatible.
obverse 6y ago
I've tried going down that rabbit hole before. The primary issue that stopped me was the different executable file formats. I never took it anywhere, but I think the way to go would be a "polyglot" script that could be interpreted by different script engines (sh/bat) that would then pick the correct executable for the given OS. This would require the user to change the file extension as well as download multiple executable files so I don't necessarily like this solution from an elegance stand point.
- sgtnoodle 6y ago
  I've had good success with shebangs combined with zip archives containing python code. Zip files use a footer rather than a header, and python natively supports executing scripts out of them. The beginning of the file can have a shebang, allowing it to specify the interpreter to use. The only trick is that windows doesn't support shebangs, and so you need to associate your chosen file extension with python on every system. Also, you need python installed obviously. What that gives you is a stable entry point into python code. From there, you can run whatever platform specific code you want.
nneonneo 6y ago
Most file formats have a magic number at offset 0. The magic numbers for EXE ("MZ"), OS X (0xfeedface/0xfeedfacf) and Linux ("\x7fELF") are all different, so they aren't compatible.
- viraptor 6y ago
  Not on windows, but that depends on the OS. On Linux the handlers are pluggable via binfmt (https://en.m.wikipedia.org/wiki/Binfmt_misc https://en.m.wikipedia.org/wiki/Binfmt_misc) and this allows for example wine and .net binaries to work transparently. (I'm not aware of it, but maybe there a similar system in windows)
- pwdisswordfish4 6y ago
  αcτµαlly pδrταblε εxεcµταblε https://news.ycombinator.com/item?id=24256883 https://news.ycombinator.com/item?id=24256883 https://justine.storage.googleapis.com/ape.html https://justine.storage.googleapis.com/ape.html
- wizzwizz4 6y ago
  The PE magic number doesn't need to be at offset zero, which is why you can do this. Mach and ELF do need to be at offset zero, so you can't have something that's Mach and ELF at the same time. In theory, this is possible, if you can recover from COM executing the header.

mehrdadn 6y ago

Do you know of a good way (if any) to shrink the size of the DOS header as much as possible on MSVC? (Like to remove the "This program cannot be run in DOS mode" notice, and other things you don't need on Windows.)

dblohm7 6y ago
It’s just a MSVC linker directive. Use /STUB
- mehrdadn 6y ago
  Yeah I tried that at some point but I didn't figure out what to feed it to make a smaller executable that would still run. Not sure what I might've done wrong unfortunately, it's been a few years.