bpo-21536: C extensions are no longer linked to libpython (GH-12946)

On Unix, C extensions are no longer linked to libpython.

It is now possible to load a C extension built using a shared library
Python with a statically linked Python.

When Python is embedded, libpython must not be loaded with
RTLD_LOCAL, but RTLD_GLOBAL instead. Previously, using RTLD_LOCAL, it
was already not possible to load C extensions which were not linked
to libpython, like C extensions of the standard library built by the
"*shared*" section of Modules/Setup.

distutils, python-config and python-config.py have been modified.
This commit is contained in:
Victor Stinner 2019-04-25 20:13:10 +02:00 committed by GitHub
parent d7befad328
commit 8c3ecc6bac
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7 changed files with 28 additions and 26 deletions

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@ -277,6 +277,10 @@ the full reference.
| | simply skip the extension. | |
+------------------------+--------------------------------+---------------------------+
.. versionchanged:: 3.8
On Unix, C extensions are no longer linked to libpython.
.. class:: Distribution

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@ -851,16 +851,19 @@ Changes in the Python API
Changes in the C API
--------------------
* On Unix, C extensions are no longer linked to libpython. When Python is
embedded, ``libpython`` must not be loaded with ``RTLD_LOCAL``, but
``RTLD_GLOBAL`` instead. Previously, using ``RTLD_LOCAL``, it was already not
possible to load C extensions which were not linked to ``libpython``, like C
extensions of the standard library built by the ``*shared*`` section of
``Modules/Setup``.
* Use of ``#`` variants of formats in parsing or building value (e.g.
:c:func:`PyArg_ParseTuple`, :c:func:`Py_BuildValue`, :c:func:`PyObject_CallFunction`,
etc.) without ``PY_SSIZE_T_CLEAN`` defined raises ``DeprecationWarning`` now.
It will be removed in 3.10 or 4.0. Read :ref:`arg-parsing` for detail.
(Contributed by Inada Naoki in :issue:`36381`.)
Changes in the C API
--------------------------
* Instances of heap-allocated types (such as those created with
:c:func:`PyType_FromSpec`) hold a reference to their type object.
Increasing the reference count of these type objects has been moved from

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@ -714,20 +714,5 @@ class build_ext(Command):
# don't extend ext.libraries, it may be shared with other
# extensions, it is a reference to the original list
return ext.libraries + [pythonlib]
else:
return ext.libraries
elif sys.platform == 'darwin':
# Don't use the default code below
return ext.libraries
elif sys.platform[:3] == 'aix':
# Don't use the default code below
return ext.libraries
else:
from distutils import sysconfig
if sysconfig.get_config_var('Py_ENABLE_SHARED'):
pythonlib = 'python{}.{}{}'.format(
sys.hexversion >> 24, (sys.hexversion >> 16) & 0xff,
sysconfig.get_config_var('ABIFLAGS'))
return ext.libraries + [pythonlib]
else:
return ext.libraries
return ext.libraries

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@ -1460,7 +1460,7 @@ libinstall: build_all $(srcdir)/Modules/xxmodule.c
-PYTHONPATH=$(DESTDIR)$(LIBDEST) $(RUNSHARED) \
$(PYTHON_FOR_BUILD) -m lib2to3.pgen2.driver $(DESTDIR)$(LIBDEST)/lib2to3/PatternGrammar.txt
python-config: $(srcdir)/Misc/python-config.in Misc/python-config.sh
python-config: $(srcdir)/Misc/python-config.in $(srcdir)/Misc/python-config.sh
@ # Substitution happens here, as the completely-expanded BINDIR
@ # is not available in configure
sed -e "s,@EXENAME@,$(BINDIR)/python$(LDVERSION)$(EXE)," < $(srcdir)/Misc/python-config.in >python-config.py

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@ -0,0 +1,12 @@
On Unix, C extensions are no longer linked to libpython.
It is now possible to load a C extension built using a shared library Python
with a statically linked Python.
When Python is embedded, ``libpython`` must not be loaded with ``RTLD_LOCAL``,
but ``RTLD_GLOBAL`` instead. Previously, using ``RTLD_LOCAL``, it was already
not possible to load C extensions which were not linked to ``libpython``, like
C extensions of the standard library built by the ``*shared*`` section of
``Modules/Setup``.
distutils, python-config and python-config.py have been modified.

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@ -47,9 +47,7 @@ for opt in opt_flags:
print(' '.join(flags))
elif opt in ('--libs', '--ldflags'):
libs = ['-lpython' + pyver + sys.abiflags]
libs += getvar('LIBS').split()
libs += getvar('SYSLIBS').split()
libs = getvar('LIBS').split() + getvar('SYSLIBS').split()
# add the prefix/lib/pythonX.Y/config dir, but only if there is no
# shared library in prefix/lib/.
if opt == '--ldflags':

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@ -41,7 +41,7 @@ LIBM="@LIBM@"
LIBC="@LIBC@"
SYSLIBS="$LIBM $LIBC"
ABIFLAGS="@ABIFLAGS@"
LIBS="-lpython${VERSION}${ABIFLAGS} @LIBS@ $SYSLIBS"
LIBS="@LIBS@ $SYSLIBS"
BASECFLAGS="@BASECFLAGS@"
LDLIBRARY="@LDLIBRARY@"
OPT="@OPT@"