Python is Actually Portable

1. Did you click on this before reading the remainder of the post because you were wondering about Python 3? I know Python 2.7 reached EOL last year, but the Python 2.7 codebase was easier to read, change, and debug, so I was able to get a better idea of where I had to make changes. I put together a Python 3.6.14 APE (build it from the repo here), and it took much less time and experimentation because I knew exactly where to look. ↩︎

2. I originally uploaded this post like twelve hours, in the excitement of seeing a Flask webapp work on the APE. Unfortunately, I forgot to test on Windows before putting the post out, and Windows, true to its nature caused several annoyances which together took a couple of hours to sort out. However, I think it ought to work now. ↩︎

3. I originally tried the complicated solution of writing a new configure script from scratch, but I got lost in the docs for autoconf, and resorted to the simpler fix of just editing the shell script. This issue only happened because I used dummy headers with the amalgamation; if you have the Cosmopolitan repo nearby, you can use -isystem cosmopolitan/libc/isystem instead of -I dummy_headers -include cosmopolitan.h, which would avoid confusing configure. ↩︎

4. I remembered this a few days back: if a name in your C file clashes with a header name somewhere, you can do something like:

   
   #ifdef name
   #define name __name
   #undef name
       
   

   and avoid the name clash instead of doing a find-and-replace. ↩︎

5. Over the course of getting the APE to work, my muscle memory is to call python -BESsuv, which avoids a bunch of normal startup stuff and adds stderr information about imports. This is super useful when building python, but one time I was running a local script and couldn’t figure out why it was failing before I saw that I had typed python -BESsuv script.py every single time. ↩︎

6. I was pleasantly surprised to find out that _sqlite and _bz2 could be compiled, because I didn’t expect SQLite or libbz2 would be easy to compile from source with Cosmopolitan. SQLite is now vendored in the Cosmopolitan repo.

   On the other hand, I wanted readline because I like to have the (press-Up-arrow-for-previously-typed-line) in the REPL, but I didn’t know how terminfo worked. _ctypes was also a disappointment because I had to compile libffi from source, and then I saw most of _ctypes' use comes from having dlopen. ↩︎

7. for example, greenlet contains a C extension called _greenlet which it refers to by doing things like the following in __init__.py:

       
   from ._greenlet import foo
   from greenlet._greenlet import bar
       
   

   now __init__.py expects _greenlet.so to be present in the same directory, but that is not possible because the extension is compiled into the interpreter statically. So I had to manually change this to use from _greenlet without the dot. This also means I have to change the extension name in the PyModuleDef part of the C source code: it’s not greenlet._greenlet anymore, it’s just _greenlet. ↩︎

8. This works because most libraries use only the high-level threading API to handle their threads. A notable counter-example is Django: I tried getting Django to work before figuring out how _greenlet could be compiled, but Django imports the low-level _thread API to handle things. ↩︎

9. It is possible to have SSL support: you just have to build OpenSSL with Cosmopolitan Libc. I was able to build libssl.a, link it with python.com via Modules/Setup, and pip worked. However, I have not tested it with the OpenSSL test suite. ↩︎

10. The Cosmopolitan repo builds python.com using PYOBJ.COM, a minimal Python executable that creates .pyc files and symbols for the linker to resolve dependencies. ↩︎