New submission from Ned Deily <n...@python.org>:
When building on macOS 11 (beta), a number of modules that should normally
build on macOS fail because the system-supplied third-party libraries are not
found.
The necessary bits to build these optional modules were not found:
_bz2 _curses _curses_panel
_gdbm _hashlib _lzma
_ssl ossaudiodev readline
spwd zlib
The list should look like this (with no additional third-party libs supplied
from another source like Homebrew or MacPorts):
The necessary bits to build these optional modules were not found:
_gdbm _hashlib _ssl
ossaudiodev spwd
The problem is due to a change in the 11 beta versus 10.15 or earlier systems:
"New in macOS Big Sur 11 beta, the system ships with a built-in dynamic linker
cache of all system-provided libraries. As part of this change, copies of
dynamic libraries are no longer present on the filesystem. Code that attempts
to check for dynamic library presence by looking for a file at a path or
enumerating a directory will fail. Instead, check for library presence by
attempting to dlopen() the path, which will correctly check for the library in
the cache."
This breaks tests in setup.py using find_library_file() to determine if a
library is present and in what directory it exists. setup.py depends on
Lib/distutils/unixccompiler.py to do the dirty work. A similar problem arose on
earlier macOS releases when header files could no longer be installed in the
systems /usr/include; setup.py had to be taught to look in the SDK being used
implicitly or explicitly by the compiler preprocessor. We could probably do
something like that here while trying to avoid changes that might break
downstream supplements/replacements to distutils, for example, setuptools.
There is a workaround: explicitly specify the SDK location to ./configure (you
also need to specify the universal archs setting):
./configure \
--enable-universalsdk=$(xcodebuild -version -sdk macosx Path) \
--with-universal-archs=intel-64 \
...
----------
components: macOS
messages: 372379
nosy: ned.deily, ronaldoussoren
priority: high
severity: normal
status: open
title: build on macOS 11 (beta) does not find system-supplied third-party
libraries
versions: Python 3.10, Python 3.7, Python 3.8, Python 3.9
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue41116>
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