Fix cross-compiling by searching the right lib and include directories - #9977
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radarhere wants to merge 1 commit into
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Fix cross-compiling by searching the right lib and include directories#9977radarhere wants to merge 1 commit into
radarhere wants to merge 1 commit into
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We were previously searching the `{sys.prefix}/lib` and
`{sys.prefix}/include` directories unconditionally. This is problematic
when cross-compiling, as it does not take account of any sysroot where
alternative libraries and headers are located. Adding `-I/usr/include`
causes the build to explode, at least when cross-compiling from 64-bit
to 32-bit.
Python does not officially support cross-compiling, but Gentoo achieves
this by modifying the sysconfig variables like `LIBDIR` and `INCLUDEDIR`
with great results.
Assuming "lib" is bad. 64-bit Linux systems often use lib64, putting
32-bit libraries under lib. You cannot assume that either though, as
pure 64-bit Linux systems may just use lib instead. Things get even
stranger on RISC-V.
The value of `sys.prefix` changes when using a virtualenv. Dependencies
may be installed here, so it does make sense to continue supporting this
case, even if it is incompatible with cross-compiling. Unlike regular
environments, "lib" is generally used for libraries, although a lib64
symlink may also be present.
akx
reviewed
Sep 9, 2026
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| (sys.prefix == sys.base_prefix and sysconfig.get_config_var("LIBDIR")) | ||
| or os.path.join(sys.prefix, "lib"), |
Contributor
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At first read, this reads like the pre-Python-2.5 pattern of COND and T or F for T if COND else F, but not quite:
There's a subtle difference here since sysconfig.get_config_var() can return None, so then we fall back to the default. 👍
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Rebase of #7634
It looks like we don't have permissions to update that PR, and it is failing to build the docs because it is out of date.