initModule symbol not visible in 1.64

[rosswhitfield]

I'm compiling a project that sets the default visibility to hidden using CMAKE_CXX_VISIBILITY_PRESET=hidden. This worked in 1.63 as the initModule is set back to default here, unfortunately after #1 BOOST_PYTHON_USE_GCC_SYMBOL_VISIBILITY is no longer defined so the visibility is not getting set back to default.

So I'm getting errors like ImportError: dynamic module does not define init function (init_kernel) and the equivalent for python 3 ImportError: dynamic module does not define module export function (PyInit__kernel)

[lukaszforynski]

This seems to be the offending change..

include/boost/python/object/instance.hpp
@@ -11,7 +11,7 @@
 
 namespace boost { namespace python
 {
-  struct BOOST_PYTHON_DECL_FORWARD instance_holder;
+  struct instance_holder;
 }} // namespace boost::python
 
 namespace boost { namespace python { namespace objects { 

Changing it back (*to what was originally intended? in #1):

include/boost/python/object/instance.hpp
@@ -11,7 +11,7 @@
 
 namespace boost { namespace python
 {
-  struct instance_holder;
+  struct BOOST_PYTHON_DECL instance_holder;

 }} // namespace boost::python
 
 namespace boost { namespace python { namespace objects { 

Seems to fix the issue.