使用虚拟方法部分导出类时出现段错误

Bor*_*ein 5 shared-libraries vtable typeinfo boost-python pybind11

^{（注：我已经在pybind11 的 GitHub上问过这个问题。为更广泛的受众提供支持。也标记 boost.python 以防有人有洞察力，但问题是如何使用 pybind11 做到这一点）}

环境：Ubuntu 18.04、GCC 7.4.0、Python 3.6.9、pybind11 2.4.3

假设我们想用 pybind11 包装一个共享库libfoo.so，导出一个基类Foo（即，使用 vtable，在本例中只是一个虚拟析构函数）。

导出整个类：好的

如果我们导出整个类（即添加visibility("default")到整个类），那么一切都会按预期进行：

CMakeLists.txt

cmake_minimum_required(VERSION 3.1.0)
add_subdirectory(pybind11)

add_library(foo SHARED foo.cpp)
set_target_properties(foo PROPERTIES CXX_VISIBILITY_PRESET hidden)

pybind11_add_module(pyfoo pyfoo.cpp)
target_link_libraries(pyfoo PRIVATE foo)

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foo.h

#define FOO_API __attribute__((visibility("default")))
class FOO_API Foo { public: virtual ~Foo(); };

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foo.cpp

#include "foo.h"
Foo::~Foo() {}

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pyfoo.cpp

#include <pybind11/pybind11.h>
#include "foo.h"
PYBIND11_MODULE(pyfoo, m) {
    pybind11::class_<Foo>(m, "Foo")
        .def(pybind11::init<>());
}

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测试.py

import pyfoo
f = pyfoo.Foo()
print("Test succeeded")

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构建并运行：

$ mkdir build && cd build && cmake .. && make
$ PYTHONPATH=. python3 ../test.py
Test succeeded

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部分导出类：Segfault

然而，我的理解是，为了最大限度地减少导出符号的数量，更好的做法是有选择地导出所需的成员函数，而不是整个类。具体示例请参见SdfDataPixar 的 USD 的一部分。

在我们的最小示例中，这将如下所示（请注意，FOO_API现在是专门为析构函数而不是整个类声明的）：

foo.h

#define FOO_API __attribute__((visibility("default")))
class  Foo { public: FOO_API virtual ~Foo(); };

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构建并运行：

$ make
$ PYTHONPATH=. python3 ../test.py
Segmentation fault (core dumped)

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（请注意，虚拟方法是析构函数还是其他方法并不重要。当整个类未导出时，仅存在虚拟方法就会导致段错误，即使此类虚拟方法没有被包装。如果我们删除就不会出现段错误virtual如果我们从上面的示例中

问题

这是一个错误吗？

如果没有，是否有任何解决方法/方法能够使用虚拟方法部分导出基类？问题似乎是共享库中缺少导出的 typeinfo/vtable：有没有办法显式导出这些内容而不必导出整个类？

更多调试信息

导出全班时：

$ nm -o -C -D *.so | grep "Foo"
libfoo.so:0000000000000818 T Foo::~Foo()
libfoo.so:00000000000007fa T Foo::~Foo()
libfoo.so:00000000000007fa T Foo::~Foo()
libfoo.so:0000000000200df8 V typeinfo for Foo
libfoo.so:000000000000084d V typeinfo name for Foo
libfoo.so:0000000000200dd8 V vtable for Foo
pyfoo.cpython-36m-x86_64-linux-gnu.so:                 U typeinfo for Foo
pyfoo.cpython-36m-x86_64-linux-gnu.so:                 U vtable for Foo

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仅导出析构函数时：

$ nm -o -C -D *.so | grep "Foo"
libfoo.so:0000000000000794 T Foo::~Foo()
libfoo.so:000000000000077a T Foo::~Foo()
libfoo.so:000000000000077a T Foo::~Foo()
pyfoo.cpython-36m-x86_64-linux-gnu.so:                 U typeinfo for Foo
pyfoo.cpython-36m-x86_64-linux-gnu.so:                 U vtable for Foo

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堆栈跟踪（段错误与调用有关import pyfoo）

$ PYTHONPATH=. gdb python3
(gdb) r ../test.py
Starting program: /usr/bin/python3 ../test.py
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff42b72a9 in GlobalError::PushToStack() () from /usr/lib/x86_64-linux-gnu/libapt-pkg.so.5.0
(gdb) bt
#0  0x00007ffff42b72a9 in GlobalError::PushToStack() () from /usr/lib/x86_64-linux-gnu/libapt-pkg.so.5.0
#1  0x00007ffff433b082 in pkgInitConfig(Configuration&) () from /usr/lib/x86_64-linux-gnu/libapt-pkg.so.5.0
#2  0x00007ffff45d8ed8 in ?? () from /usr/lib/python3/dist-packages/apt_pkg.cpython-36m-x86_64-linux-gnu.so
#3  0x000000000050a8af in ?? ()
#4  0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#5  0x0000000000508245 in ?? ()
#6  0x00000000005167b9 in ?? ()
#7  0x00000000005678ee in PyCFunction_Call ()
#8  0x000000000051171e in _PyEval_EvalFrameDefault ()
#9  0x0000000000508245 in ?? ()
#10 0x000000000050a080 in ?? ()
#11 0x000000000050aa7d in ?? ()
#12 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#13 0x0000000000509d48 in ?? ()
#14 0x000000000050aa7d in ?? ()
#15 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#16 0x0000000000509d48 in ?? ()
#17 0x000000000050aa7d in ?? ()
#18 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#19 0x0000000000509d48 in ?? ()
#20 0x000000000050aa7d in ?? ()
#21 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#22 0x0000000000509455 in _PyFunction_FastCallDict ()
#23 0x00000000005a55a1 in _PyObject_FastCallDict ()
#24 0x00000000005a65de in _PyObject_CallMethodIdObjArgs ()
#25 0x00000000004f729d in PyImport_ImportModuleLevelObject ()
#26 0x000000000050e4f1 in _PyEval_EvalFrameDefault ()
#27 0x0000000000508245 in ?? ()
#28 0x00000000005167b9 in ?? ()
#29 0x00000000005678ee in PyCFunction_Call ()
#30 0x000000000051171e in _PyEval_EvalFrameDefault ()
#31 0x0000000000508245 in ?? ()
#32 0x000000000050a080 in ?? ()
#33 0x000000000050aa7d in ?? ()
#34 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#35 0x0000000000509d48 in ?? ()
#36 0x000000000050aa7d in ?? ()
#37 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#38 0x0000000000509d48 in ?? ()
#39 0x000000000050aa7d in ?? ()
#40 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#41 0x0000000000509d48 in ?? ()
#42 0x000000000050aa7d in ?? ()
#43 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#44 0x0000000000509455 in _PyFunction_FastCallDict ()
#45 0x00000000005a55a1 in _PyObject_FastCallDict ()
#46 0x00000000005a65de in _PyObject_CallMethodIdObjArgs ()
#47 0x00000000004f729d in PyImport_ImportModuleLevelObject ()
#48 0x000000000050e4f1 in _PyEval_EvalFrameDefault ()
#49 0x0000000000508245 in ?? ()
#50 0x00000000005167b9 in ?? ()
#51 0x00000000005678ee in PyCFunction_Call ()
#52 0x000000000051171e in _PyEval_EvalFrameDefault ()
#53 0x0000000000508245 in ?? ()
#54 0x000000000050a080 in ?? ()
#55 0x000000000050aa7d in ?? ()
#56 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#57 0x0000000000509d48 in ?? ()
#58 0x000000000050aa7d in ?? ()
#59 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#60 0x0000000000509d48 in ?? ()
#61 0x000000000050aa7d in ?? ()
#62 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#63 0x0000000000509d48 in ?? ()
#64 0x000000000050aa7d in ?? ()
#65 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#66 0x0000000000509455 in _PyFunction_FastCallDict ()
#67 0x00000000005a55a1 in _PyObject_FastCallDict ()
#68 0x00000000005a65de in _PyObject_CallMethodIdObjArgs ()
#69 0x00000000004f729d in PyImport_ImportModuleLevelObject ()
#70 0x000000000050e4f1 in _PyEval_EvalFrameDefault ()
#71 0x0000000000508245 in ?? ()
#72 0x00000000005167b9 in ?? ()
#73 0x00000000005678ee in PyCFunction_Call ()
#74 0x000000000051171e in _PyEval_EvalFrameDefault ()
#75 0x0000000000508245 in ?? ()
#76 0x000000000050a080 in ?? ()
#77 0x000000000050aa7d in ?? ()
#78 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#79 0x0000000000509d48 in ?? ()
---Type <return> to continue, or q <return> to quit---
#80 0x000000000050aa7d in ?? ()
#81 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#82 0x0000000000509d48 in ?? ()
#83 0x000000000050aa7d in ?? ()
#84 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#85 0x0000000000509d48 in ?? ()
#86 0x000000000050aa7d in ?? ()
#87 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#88 0x0000000000509455 in _PyFunction_FastCallDict ()
#89 0x00000000005a55a1 in _PyObject_FastCallDict ()
#90 0x00000000005a65de in _PyObject_CallMethodIdObjArgs ()
#91 0x00000000004f729d in PyImport_ImportModuleLevelObject ()
#92 0x000000000050e4f1 in _PyEval_EvalFrameDefault ()
#93 0x0000000000508245 in ?? ()
#94 0x00000000005167b9 in ?? ()
#95 0x00000000005678ee in PyCFunction_Call ()
#96 0x000000000051171e in _PyEval_EvalFrameDefault ()
#97 0x0000000000508245 in ?? ()
#98 0x000000000050a080 in ?? ()
#99 0x000000000050aa7d in ?? ()
#100 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#101 0x0000000000509d48 in ?? ()
#102 0x000000000050aa7d in ?? ()
#103 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#104 0x0000000000509d48 in ?? ()
#105 0x000000000050aa7d in ?? ()
#106 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#107 0x0000000000509d48 in ?? ()
#108 0x000000000050aa7d in ?? ()
#109 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#110 0x0000000000509455 in _PyFunction_FastCallDict ()
#111 0x00000000005a55a1 in _PyObject_FastCallDict ()
#112 0x00000000005a65de in _PyObject_CallMethodIdObjArgs ()
#113 0x00000000004f729d in PyImport_ImportModuleLevelObject ()
#114 0x0000000000514804 in ?? ()
#115 0x00000000005678b3 in PyCFunction_Call ()
#116 0x000000000051171e in _PyEval_EvalFrameDefault ()
#117 0x0000000000508245 in ?? ()
#118 0x000000000050a080 in ?? ()
#119 0x000000000050aa7d in ?? ()
#120 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#121 0x0000000000509d48 in ?? ()
#122 0x000000000050aa7d in ?? ()
#123 0x000000000050c5b9 in _PyEval_EvalFrameDefault ()
#124 0x0000000000509455 in _PyFunction_FastCallDict ()
#125 0x00000000005a55a1 in _PyObject_FastCallDict ()
#126 0x00000000005a65de in _PyObject_CallMethodIdObjArgs ()
#127 0x00000000004f729d in PyImport_ImportModuleLevelObject ()
#128 0x000000000050e4f1 in _PyEval_EvalFrameDefault ()
#129 0x0000000000509455 in _PyFunction_FastCallDict ()
#130 0x00000000005a55a1 in _PyObject_FastCallDict ()
#131 0x00000000006386cb in PyErr_PrintEx ()
#132 0x0000000000638ab3 in PyRun_SimpleFileExFlags ()
#133 0x0000000000639631 in Py_Main ()
#134 0x00000000004b0f40 in main ()

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