4 ms·

Can someone eli5 how this works? I sort of get that you can create one big binary file with all the necessary file headers for each platform and the actual x86

Can someone eli5 how this works? I sort of get that you can create one big binary file with all the necessary file headers for each platform and the actual x86 code being shared, but what about stuff like syscalls? The post also lost me when it started mentioning the need for shell scripts and emulators.

Mathnerd314 6y ago
He talks about it a bit as the "magic numbers". You can see the big table: https://github.com/jart/cosmopolitan/blob/c91b3c50068224929cd4d3ddf36c5a10254cbd9c/libc/sysv/consts.sh https://github.com/jart/cosmopolitan/blob/c91b3c50068224929c... I guess there's also syscall emulation stubs for Windows but since he only supports "stdio and sockets" maybe not.
- reallyeli 6y ago
  The author is a "she": https://en.wikipedia.org/wiki/Justine_Tunney https://en.wikipedia.org/wiki/Justine_Tunney
  - Rebelgecko 6y ago
    "Tunney has described Occupy Wall Street as a far-left movement.[13] Her former comrades have described her as a technocratic fascist.[14]" Wow, although I'm not familiar with her, this wiki article seems a bit melodramatic
    - jessaustin 6y ago
      How on earth has that article met the "notability" threshold?
      - mlindner 6y ago
        Well she owns/owned the Occupy Wallstreet twitter account.
    - cringepirate 6y ago
      I remember this person, she was on Gavin McInnes podcast quite a while ago. Here is the interview: https://www.dailymotion.com/video/x2ke4nq https://www.dailymotion.com/video/x2ke4nq
    - mlindner 6y ago
      Listening to her talk, she seems a pretty standard run of the mill Libertarian with a blend of technocrat.
  - userbinator 6y ago
    Reading that page, and this HN article, reminds me of a classic phrase: "There is a fine line between genius and insanity."
    - deleted 6y ago
      [deleted]
  - GoblinSlayer 6y ago
    >technocratic fascist >zealous googler At this rate GPL2 will stand for Google Public License.
ChrisSD 6y ago
You can read more in the libc source. The readme gives an overview. https://github.com/jart/cosmopolitan/tree/master/libc https://github.com/jart/cosmopolitan/tree/master/libc
tbodt 6y ago
It turns out to be impossible to create a file that is simultaneously a valid ELF and Windows PE. The solution to this is to make a file that is simultaneously a valid PE and shell script, and have the shell script overwrite the start of the file with an ELF header and re-exec itself.
- krackers 6y ago
  Ah thank you. And I presume the qemu part is optional, used only when the target platform is non x86?
- StavrosK 6y ago
  That means you can't copy the executable after executing once and have it run on Windows, correct?
  - shandor 6y ago
    Probably the rewriting is only done on the program loaded into RAM?
    - StavrosK 6y ago
      Hmm, possibly, though that wouldn't really make sense, why not just execute itself at that point?
    - yjftsjthsd-h 6y ago
      No, there's a discussion upthread about running on Darwin that specifically says you have to run as `bash ./foo` first time and `./foo` thereafter because it overwrites on disk.

Mathnerd314 6y ago

He talks about it a bit as the "magic numbers". You can see the big table: https://github.com/jart/cosmopolitan/blob/c91b3c50068224929cd4d3ddf36c5a10254cbd9c/libc/sysv/consts.sh https://github.com/jart/cosmopolitan/blob/c91b3c50068224929c... I guess there's also syscall emulation stubs for Windows but since he only supports "stdio and sockets" maybe not.

reallyeli 6y ago
The author is a "she": https://en.wikipedia.org/wiki/Justine_Tunney https://en.wikipedia.org/wiki/Justine_Tunney
- Rebelgecko 6y ago
  "Tunney has described Occupy Wall Street as a far-left movement.[13] Her former comrades have described her as a technocratic fascist.[14]" Wow, although I'm not familiar with her, this wiki article seems a bit melodramatic
  - jessaustin 6y ago
    How on earth has that article met the "notability" threshold?
    - mlindner 6y ago
      Well she owns/owned the Occupy Wallstreet twitter account.
  - cringepirate 6y ago
    I remember this person, she was on Gavin McInnes podcast quite a while ago. Here is the interview: https://www.dailymotion.com/video/x2ke4nq https://www.dailymotion.com/video/x2ke4nq
  - mlindner 6y ago
    Listening to her talk, she seems a pretty standard run of the mill Libertarian with a blend of technocrat.
- userbinator 6y ago
  Reading that page, and this HN article, reminds me of a classic phrase: "There is a fine line between genius and insanity."
  - deleted 6y ago
    [deleted]
- GoblinSlayer 6y ago
  >technocratic fascist >zealous googler At this rate GPL2 will stand for Google Public License.

ChrisSD 6y ago

You can read more in the libc source. The readme gives an overview. https://github.com/jart/cosmopolitan/tree/master/libc https://github.com/jart/cosmopolitan/tree/master/libc

tbodt 6y ago

It turns out to be impossible to create a file that is simultaneously a valid ELF and Windows PE. The solution to this is to make a file that is simultaneously a valid PE and shell script, and have the shell script overwrite the start of the file with an ELF header and re-exec itself.

krackers 6y ago
Ah thank you. And I presume the qemu part is optional, used only when the target platform is non x86?
StavrosK 6y ago
That means you can't copy the executable after executing once and have it run on Windows, correct?
- shandor 6y ago
  Probably the rewriting is only done on the program loaded into RAM?
  - StavrosK 6y ago
    Hmm, possibly, though that wouldn't really make sense, why not just execute itself at that point?
  - yjftsjthsd-h 6y ago
    No, there's a discussion upthread about running on Darwin that specifically says you have to run as `bash ./foo` first time and `./foo` thereafter because it overwrites on disk.