Fixed compile visibility issue

CMakeLists.txt

@@ -68,7 +68,7 @@ target_compile_features(${module_name} PRIVATE cxx_std_14)
 
 target_compile_options(${module_name} PRIVATE
     $<$<OR:$<CXX_COMPILER_ID:Clang>,$<CXX_COMPILER_ID:AppleClang>,$<CXX_COMPILER_ID:GNU>>:
-    -Wall -Wextra -Wold-style-cast -Winline -pedantic -Werror=narrowing -Wshadow $<$<BOOL:${WERROR}>:-Werror>>)
+    -Wall -Wextra -Wold-style-cast -Winline -pedantic -Werror=narrowing -fvisibility=hidden -Wshadow $<$<BOOL:${WERROR}>:-Werror>>)
 target_compile_options(${module_name} PRIVATE
     $<$<CXX_COMPILER_ID:MSVC>:
     /W4>)

include/aidge/utils/DynamicAttributes.hpp

@@ -183,6 +183,10 @@ private:
 
 #ifdef PYBIND
     // Stores C++ attributes (copy) and Python-only attributes
+    // Code should be compiled with -fvisibility=hidden
+    // See https://pybind11.readthedocs.io/en/stable/faq.html:
+    // “‘SomeClass’ declared with greater visibility than the type of its 
+    // field ‘SomeClass::member’ [-Wattributes]”
     std::map<std::string, py::object> mAttrsPy;
 #endif
 };