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What is libpython3.so compared to libpython3.5m.so built from python 3.5.2 source?

In my application, I use boost_python and python 3.5.2. Everything is built from source in Ubuntu 14.

When I built Python 3.5.2 from a source with parameters --with-sharedin Ubuntu, I got libpython3.so(7.6kB) and libpython3.5m.so(12MB). I assume that the big one is real, and the small one may be something that forwards calls to real interfaces.

How boost_python can assume that the client is communicating with python ( https://svn.boost.org/trac/boost/ticket/2615 ), I linked libpython3.sowith my application. But when I run it, I got an error of unresolved characters.

ldd -r myappor ldd -r libboost_python.soboth listed all python characters were not allowed, which can be found in nm -D libpython3.5m.so.

# ldd -r lib/libboost_python3.so
    linux-vdso.so.1 => (0x00007ffe767fb000)
    libstdc+.so.6 => /usr/lib/x86_64-linux-gnu/libstdc+.so.6 (0x00007f130a7a3000)
    libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f130a58d000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f130a1c8000)
    libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f1309ec2000)
    /lib64/ld-linux-x86-64.so.2 (0x00007f130acf4000)
undefined symbol: PyExc_ImportError (lib/libboost_python3.so)
undefined symbol: PyProperty_Type (lib/libboost_python3.so)
undefined symbol: PyExc_StopIteration (lib/libboost_python3.so)
undefined symbol: PyBool_Type (lib/libboost_python3.so)
undefined symbol: PyExc_ValueError (lib/libboost_python3.so)
undefined symbol: PyList_Type (lib/libboost_python3.so)
undefined symbol: _Py_NotImplementedStruct (lib/libboost_python3.so)
undefined symbol: PyExc_TypeError (lib/libboost_python3.so)
undefined symbol: PyDict_Type (lib/libboost_python3.so)
...

libpython3.sodepends on libpython3.5m.so, but itself does not have these characters.

I think based on this, I should associate my application with libpython3.5m.soinstead libpython3.so. But it is strange that if I use LD_PRELOAD to load libpython3.so, these characters are inldd -r libboost_python3.so

# LD_LIBRARY_PATH=lib LD_PRELOAD=lib/libpython3.so ldd -r lib/libboost_python3.so
    linux-vdso.so.1 => (0x00007ffcb51f0000)
    lib/libpython3.so (0x00007f6f728e3000)
    libstdc+.so.6 => /usr/lib/x86_64-linux-gnu/libstdc+.so.6     (0x00007f6f725df000)
    libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f6f723c9000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f6f72004000)
    libpython3.5m.so.1.0 => lib/libpython3.5m.so.1.0 (0x00007f6f71ae1000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0     (0x00007f6f718c3000)
    libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f6f715bd000)
    /lib64/ld-linux-x86-64.so.2 (0x00007f6f72d32000)
    libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f6f713b9000)
    libutil.so.1 => /lib/x86_64-linux-gnu/libutil.so.1 (0x00007f6f711b6000)

Why is it needed libpython3.soand how to use it? Or am I just using it libpython3.5m.sodirectly?

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1 answer

The library libpython3.sosupports PEP 384 - Definition of stable ABI .

Python ABI C (, 3.4 3.5). , , .. ABI, .

Stable ABI PEP API Python C, , Python, . , Python .

, ABI, , . Python 3.5.x -lpython3.5m. Python 3.6.x -lpython3.6m. libpython3.so .

libpython3.so : Python 3.5 libpython3.5m.so, 3.6 libpython3.6m.so .. , -lpython3, Python, .

: , , ABI ( , libboost_python ABI), , , libpython3.5m.so.

, : , segfault - ABI, Python.

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Source: https://habr.com/ru/post/1607124/

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