libxml2: Fix python build & import

[star-hengxing]

Upstream report: https://gitlab.gnome.org/GNOME/libxml2/-/issues/824

• Fix static/shared build for python interface.
• Automatically set config. libxml2: use if statement instead of assert #5912

[star-hengxing]

@waruqi 请帮忙调试 mac 上的问题。

已知信息：

• 所有 python 产物都在 <installdir>/python 目录，并加上 PYTHONPATH。
• 静态链接 python3.13 和 libxml2 依然报错，应该和 python 版本 & 各种环境变量 path 加载无关。
• 链接有一些奇怪 warning。

/Applications/Xcode_15.4.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc  -pedantic -Wall -Wextra -Wshadow -Wpointer-arith -Wcast-align -Wwrite-strings -Wstrict-prototypes -Wmissing-prototypes -Wno-long-long -Wno-format-extra-args  -O3 -DNDEBUG -arch arm64 -isysroot /Applications/Xcode_15.4.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.5.sdk -dynamiclib -Wl,-headerpad_max_install_names -current_version 2.13.4 -o libxml2mod.2.13.4.dylib -install_name @rpath/libxml2mod.2.13.4.dylib "CMakeFiles/LibXml2Mod.dir/libxml2-py.c.o" CMakeFiles/LibXml2Mod.dir/python/libxml.c.o CMakeFiles/LibXml2Mod.dir/python/types.c.o  libxml2.a /Users/runner/.xmake/packages/p/python/3.13.0/3dd64f01e26f48debd2ccd8c08fdb2a3/lib/libpython3.13.a -ldl -lm /Users/runner/.xmake/packages/l/libiconv/1.17/035a4b093d48429a8f361b4ea32b4663/lib/libiconv.a -ldl -framework CoreFoundation
ld: warning: ignoring duplicate libraries: '-ldl'
ld: warning: search path '/opt/homebrew/Cellar/gcc/14.2.0/lib/gcc/14/' not found
ld: warning: object file (/Users/runner/.xmake/packages/p/python/3.13.0/3dd64f01e26f48debd2ccd8c08fdb2a3/lib/libpython3.13.a[2](getbuildinfo.o)) was built for newer 'macOS' version (14.5) than being linked (14.0)

python3 -c "import libxml2"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
    import libxml2
  File "/Users/runner/.xmake/packages/l/libxml2/v2.13.4/def471559399468b8c364a8c7c220590/python/libxml2.py", line 1, in <module>
    import libxml2mod
ModuleNotFoundError: No module named 'libxml2mod'

[waruqi]

这边检测 python 都没过，还是找的系统的 python2.7

-- The C compiler identification is AppleClang 16.0.0.16000026
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefaul
t.xctoolchain/usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Found PkgConfig: /usr/local/bin/pkg-config (found version "0.29.2")
-- Looking for include file unistd.h
-- Looking for include file unistd.h - found
-- Looking for F_GETFL
-- Looking for F_GETFL - found
CMake Error at /usr/local/Cellar/cmake/3.25.3/share/cmake/Modules/FindPackageHandleStandardArgs.cm
ake:230 (message):
  Could NOT find Python (missing: Development Development.Module
  Development.Embed) (found version "2.7.17")
Call Stack (most recent call first):
  /usr/local/Cellar/cmake/3.25.3/share/cmake/Modules/FindPackageHandleStandardArgs.cmake:600 (_FPH
SA_FAILURE_MESSAGE)
  /usr/local/Cellar/cmake/3.25.3/share/cmake/Modules/FindPython.cmake:561 (find_package_handle_sta
ndard_args)
  CMakeLists.txt:69 (find_package)

[star-hengxing]

这边检测 python 都没过，还是找的系统的 python2.7

这是啥环境，ci 上这里没问题。

-- Found Python: /Users/runner/.xmake/packages/p/python/3.13.0/3dd64f01e26f48debd2ccd8c08fdb2a3/bin/python3.13 (found version "3.13.0") found components: Interpreter Development Development.Module Development.Embed
-- Performing Test Iconv_IS_BUILT_IN
-- Performing Test Iconv_IS_BUILT_IN - Failed
-- Found Iconv: /Users/runner/.xmake/packages/l/libiconv/1.17/035a4b093d48429a8f361b4ea32b4663/lib/libiconv.a (found version "1.17")

[Issues-translate-bot]

Bot detected the issue body's language is not English, translate it automatically.

---

The python test here has not passed, but I still looked for the system’s python2.7

What kind of environment is this? There is no problem here on ci.

-- Found Python: /Users/runner/.xmake/packages/p/python/3.13.0/3dd64f01e26f48debd2ccd8c08fdb2a3/bin/python3.13 (found version "3.13.0") found components: Interpreter Development Development.Module Development.Embed
-- Performing Test Iconv_IS_BUILT_IN
-- Performing Test Iconv_IS_BUILT_IN - Failed
-- Found Iconv: /Users/runner/.xmake/packages/l/libiconv/1.17/035a4b093d48429a8f361b4ea32b4663/lib/libiconv.a (found version "1.17")

[waruqi]

macos 下有几个问题

1. 目前生成的是 libxml2mod.dylib， 得改成 libxml2mod.so 或者 xml2mod.so ，并且 import("xml2mod") 才能找到，否则是找不到的，参考 https://github.com/xmake-io/xmake/blob/46b99517934618116d6b280ffac819ba830af7db/xmake/rules/python/xmake.lua#L42
2. macos 下编译模块，不能显式加 -lpython link，并且要加 -undefined dynamic_lookup，否则即使 import 找到了，也是会 segment fault，参考：尝试使用pybind11做python的绑定，按照文档操作无果 xmake#2177 (comment) https://github.com/xmake-io/xmake/blob/46b99517934618116d6b280ffac819ba830af7db/xmake/rules/python/xmake.lua#L49C40-L49C65

而cmakelists.txt 里面，它直接加了 Python link，没对 macos 做特殊处理，应该仅仅支持 linux

目前这边本地测试通过

python3 -c "import libxml2"
  => install libxml2 v2.13.4 .. ok

[Issues-translate-bot]

Bot detected the issue body's language is not English, translate it automatically.

---

There are several problems under macos

1. Currently, libxml2mod.dylib is generated. It must be changed to libxml2mod.so or xml2mod.so and import("xml2mod") is used to find it. Otherwise, it cannot be found. Please refer to https://github.com/xmake-io/xmake/blob/46b99517934618116d6b280ffac819ba830af7db/xmake/rules/python/xmake.lua#L42
2. When compiling modules under macos, you cannot explicitly add -lpython link, and you must add -undefined dynamic_lookup, otherwise even if the import is found, segment fault will occur. Reference: https://github.com/xmake-io /xmake/issues/2177#issuecomment-1209423820 https://github.com/xmake-io/xmake/blob/46b99517934618116d6b280ffac819ba830af7db/xmake/rules/python/xmake.lua#L49C40-L49C65

In cmakelists.txt, it directly adds the Python link. No special processing is done for macos. It should only support linux.

At present, the local test here has passed

python3 -c "import libxml2"
  => install libxml2 v2.13.4 .. ok