Fix a regression in include paths when compiling ctypes in 3.6.15/3.7.12 #2209
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….12. In my previous work on getting Python 3.6.15 and 3.7.12 to compile on Apple M1, I backported logic from newer 3.8.x releases to properly find libffi and related files on macOS. This regressed compilation on Linux. The include search path was incomplete, and `ffi.h` could not be found, resulting in `ctypes` being disabled. There was a key difference between the old logic and new logic that led to this regression: 1. In 3.8 and newer, `detect_ctypes()` in `setup.py` took no arguments, and was expected to access instance variables for the include search path. 2. In 3.7 and earlier, `detect_ctypes()` took the path as an argument, and was expected to make use of it. The backport made use of the instance variables, overriding the provided include path. These were not equivalent. The one on the instance was not complete, lacking the necessary directories to find `ffi.h`. Since this could not be found, `ctypes` support was disabled. The fix is to simply not overwrite the variables passed to the function, and resume using them as before. Fixes pyenv#2207
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Description
In my previous work on getting Python 3.6.15 and 3.7.12 to compile on Apple M1, I backported logic from newer 3.8.x releases to properly find libffi and related files on macOS.
This regressed compilation on Linux. The include search path was incomplete, and
ffi.hcould not be found, resulting inctypesbeing disabled.There was a key difference between the old logic and new logic that led to this regression:
detect_ctypes()insetup.pytook no arguments, and was expected to access instance variables for the include search path.detect_ctypes()took the path as an argument, and was expected to make use of it.The backport made use of the instance variables, overriding the provided include path. These were not equivalent. The one on the instance was not complete, lacking the necessary directories to find
ffi.h. Since this could not be found,ctypessupport was disabled.The fix is to simply not overwrite the variables passed to the function, and resume using them as before.
Fixes #2207
Tests
Compiled 3.6.15 and 3.7.12 on macOS (M1).
Compiled 3.6.15 and 3.7.12 on Linux in a Docker image provided on #2207 that reproduced the failure case.
In all tested environments,
ctypescompiled and could be imported successfully.