It seems like BOOST_PYTHON_USE_GCC_SYMBOL_VISIBILITY is gone in boost1.65.1 but is still referenced in module_init.hpp. This results in failure to export PyInit_mymodule when compiling with hidden visibility and g++.

I have worked around this by add -DBOOST_PYTHON_USE_GCC_SYMBOL_VISIBILITY=1 in my sources. But previous boost did the right thing here.

Maybe the condition path elif BOOST_PYTHON_USE_GCC_SYMBOL_VISIBILITY can be dropped, adn the default fall through should be adjusted to become:

-extern "C" _BOOST_PYTHON_MODULE_INIT(name)
+extern "C" BOOST_SYMBOL_EXPORT _BOOST_PYTHON_MODULE_INIT(name)

As BOOST_SYMBOL_EXPORT defines the right thing for the right compiler, for g++ it adds __attribute__((__visibility__("default"))) no? or maybe use BOOST_SYMBOL_VISIBLE ?

I will provide a short sample and build logs.