bpo-21536: On Cygwin, C extensions must be linked with libpython (GH-13549)
It is also possible to link against a library or executable with a statically linked libpython, but not both with the same DLL. In fact building a statically linked python is currently broken on Cygwin for other (related) reasons. The same problem applies to other POSIX-like layers over Windows (MinGW, MSYS) but Python's build system does not seem to attempt to support those platforms at the moment.
This commit is contained in:
E. M. Bray
Victor Stinner
parent
438a12dd9d
commit
c994c8fc19
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@ -290,7 +290,7 @@ the full reference.
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.. versionchanged:: 3.8
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On Unix, C extensions are no longer linked to libpython except on
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Android.
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Android and Cygwin.
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.. class:: Distribution
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@ -138,7 +138,8 @@ environment variable, can be set using the new ``./configure --with-trace-refs``
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build option.
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(Contributed by Victor Stinner in :issue:`36465`.)
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On Unix, C extensions are no longer linked to libpython except on Android.
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On Unix, C extensions are no longer linked to libpython except on Android
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and Cygwin.
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It is now possible
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for a statically linked Python to load a C extension built using a shared
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library Python.
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@ -163,8 +164,8 @@ previous command fails (replace ``X.Y`` with the Python version).
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On the other hand, ``pkg-config python3.8 --libs`` no longer contains
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``-lpython3.8``. C extensions must not be linked to libpython (except on
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Android, case handled by the script); this change is backward incompatible on
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purpose.
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Android and Cygwin, whose cases are handled by the script);
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this change is backward incompatible on purpose.
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(Contributed by Victor Stinner in :issue:`36721`.)
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f-strings now support = for quick and easy debugging
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@ -1061,12 +1062,12 @@ Changes in the C API
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instead.
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(Contributed by Victor Stinner in :issue:`36728`.)
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* On Unix, C extensions are no longer linked to libpython except on
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Android. When Python is embedded, ``libpython`` must not be loaded with
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* On Unix, C extensions are no longer linked to libpython except on Android
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and Cygwin. When Python is embedded, ``libpython`` must not be loaded with
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``RTLD_LOCAL``, but ``RTLD_GLOBAL`` instead. Previously, using
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``RTLD_LOCAL``, it was already not possible to load C extensions which were
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not linked to ``libpython``, like C extensions of the standard library built
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by the ``*shared*`` section of ``Modules/Setup``.
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``RTLD_LOCAL``, it was already not possible to load C extensions which
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were not linked to ``libpython``, like C extensions of the standard
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library built by the ``*shared*`` section of ``Modules/Setup``.
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* Use of ``#`` variants of formats in parsing or building value (e.g.
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:c:func:`PyArg_ParseTuple`, :c:func:`Py_BuildValue`, :c:func:`PyObject_CallFunction`,
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@ -714,20 +714,32 @@ class build_ext(Command):
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# don't extend ext.libraries, it may be shared with other
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# extensions, it is a reference to the original list
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return ext.libraries + [pythonlib]
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# On Android only the main executable and LD_PRELOADs are considered
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# to be RTLD_GLOBAL, all the dependencies of the main executable
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# remain RTLD_LOCAL and so the shared libraries must be linked with
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# libpython when python is built with a shared python library (issue
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# bpo-21536).
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else:
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# On Android only the main executable and LD_PRELOADs are considered
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# to be RTLD_GLOBAL, all the dependencies of the main executable
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# remain RTLD_LOCAL and so the shared libraries must be linked with
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# libpython when python is built with a shared python library (issue
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# bpo-21536).
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# On Cygwin (and if required, other POSIX-like platforms based on
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# Windows like MinGW) it is simply necessary that all symbols in
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# shared libraries are resolved at link time.
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from distutils.sysconfig import get_config_var
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link_libpython = False
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if get_config_var('Py_ENABLE_SHARED'):
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# Either a native build on an Android device or the
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# cross-compilation of Python.
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if (hasattr(sys, 'getandroidapilevel') or
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('_PYTHON_HOST_PLATFORM' in os.environ and
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get_config_var('ANDROID_API_LEVEL') != 0)):
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ldversion = get_config_var('LDVERSION')
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return ext.libraries + ['python' + ldversion]
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# A native build on an Android device or on Cygwin
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if hasattr(sys, 'getandroidapilevel'):
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link_libpython = True
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elif sys.platform == 'cygwin':
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link_libpython = True
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elif '_PYTHON_HOST_PLATFORM' in os.environ:
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# We are cross-compiling for one of the relevant platforms
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if get_config_var('ANDROID_API_LEVEL') != 0:
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link_libpython = True
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elif get_config_var('MACHDEP') == 'cygwin':
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link_libpython = True
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if link_libpython:
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ldversion = get_config_var('LDVERSION')
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return ext.libraries + ['python' + ldversion]
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return ext.libraries
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@ -1052,7 +1052,8 @@ Remove the stale scriptsinstall Makefile target.
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.. nonce: ACQkiC
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.. section: Build
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On Unix, C extensions are no longer linked to libpython except on Android.
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On Unix, C extensions are no longer linked to libpython except on Android
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and Cygwin.
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It is now possible for a statically linked Python to load a C extension
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built using a shared library Python.
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@ -15129,9 +15129,9 @@ LDVERSION='$(VERSION)$(ABIFLAGS)'
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{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $LDVERSION" >&5
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$as_echo "$LDVERSION" >&6; }
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# On Android the shared libraries must be linked with libpython.
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# On Android and Cygwin the shared libraries must be linked with libpython.
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if test -z "$ANDROID_API_LEVEL"; then
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if test -z "$ANDROID_API_LEVEL" -o "$MACHDEP" != "cygwin"; then
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LIBPYTHON=''
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else
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LIBPYTHON="-lpython${VERSION}${ABIFLAGS}"
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@ -4620,9 +4620,9 @@ AC_MSG_CHECKING(LDVERSION)
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LDVERSION='$(VERSION)$(ABIFLAGS)'
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AC_MSG_RESULT($LDVERSION)
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# On Android the shared libraries must be linked with libpython.
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# On Android and Cygwin the shared libraries must be linked with libpython.
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AC_SUBST(LIBPYTHON)
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if test -z "$ANDROID_API_LEVEL"; then
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if test -z "$ANDROID_API_LEVEL" -o "$MACHDEP" != "cygwin"; then
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LIBPYTHON=''
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else
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LIBPYTHON="-lpython${VERSION}${ABIFLAGS}"
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