[DL] store extra functions in exported wrapper

Author: tttapa

interfaces/python/CMakeLists.txt

@@ -67,7 +67,9 @@ target_include_directories(_alpaqa PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/src)
 target_link_libraries(_alpaqa PRIVATE pybind11::pybind11 alpaqa::alpaqa)
 target_link_libraries(_alpaqa PRIVATE alpaqa::warnings)
 target_compile_definitions(_alpaqa PRIVATE
-    MODULE_NAME=$<TARGET_FILE_BASE_NAME:_alpaqa>)
+    MODULE_NAME=$<TARGET_FILE_BASE_NAME:_alpaqa>
+    PYBIND11_NAMESPACE=pybind11 # prevent visibility hidden in pybind11 common.h
+)
 set_target_properties(_alpaqa PROPERTIES
     CXX_VISIBILITY_PRESET "hidden"
     VISIBILITY_INLINES_HIDDEN true

interfaces/python/src/problem/problems.py.cpp

@@ -32,6 +32,8 @@ using namespace py::literals;
 #if ALPAQA_WITH_DL
 template class ALPAQA_PYTHON_EXPORT std::span<std::string_view>;
 template class ALPAQA_PYTHON_EXPORT std::tuple<py::args, py::kwargs>;
+template class ALPAQA_PYTHON_EXPORT
+    alpaqa::detail::function_wrapper_t<py::object(void *, py::args, py::kwargs)>;
 #endif
 
 #include <util/copy.hpp>

src/interop/dl-api/include/alpaqa/dl/dl-problem.h

@@ -7,6 +7,18 @@
 
 #define ALPAQA_DL_ABI_VERSION 0xA1A000000004
 
+#ifdef _WIN32
+#ifdef ALPAQA_DL_PROBLEM_EXPORTS // TODO: what's the right approach on Windows?
+#define ALPAQA_DL_PROBLEM_EXPORT __declspec(dllexport)
+#else
+#define ALPAQA_DL_PROBLEM_EXPORT __declspec(dllimport)
+#endif
+#elif defined(__GNUC__)
+#define ALPAQA_DL_PROBLEM_EXPORT __attribute__((visibility("default")))
+#else
+#define ALPAQA_DL_PROBLEM_EXPORT
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #define ALPAQA_BEGIN_STRUCT(name) struct name
@@ -654,6 +666,13 @@ using control_problem_register_t  = alpaqa_control_problem_register_t;
 using problem_functions_t         = alpaqa_problem_functions_t;
 using control_problem_functions_t = alpaqa_control_problem_functions_t;
 
+namespace detail {
+template <class Signature>
+struct ALPAQA_DL_PROBLEM_EXPORT function_wrapper_t {
+    std::function<Signature> function;
+};
+} // namespace detail
+
 /// Make the given function available to alpaqa.
 /// @see @ref alpaqa::dl::DLProblem::call_extra_func
 /// @see @ref alpaqa::dl::DLControlProblem::call_extra_func
@@ -663,7 +682,8 @@ void register_function(function_dict_t *&extra_functions, std::string name,
     if (extra_functions == nullptr)
         extra_functions = new function_dict_t{};
     extra_functions->dict.insert_or_assign(
-        std::move(name), std::function{std::forward<Func>(func)});
+        std::move(name),
+        detail::function_wrapper_t{std::function{std::forward<Func>(func)}});
 }
 
 template <class Func>

src/interop/dl/include/alpaqa/dl/dl-problem.hpp

@@ -38,7 +38,8 @@ class ExtraFuncs {
             throw std::out_of_range("DLProblem: no extra function named \"" +
                                     name + '"');
         try {
-            return std::any_cast<const std::function<Signature> &>(it->second);
+            using func_t = detail::function_wrapper_t<Signature>;
+            return std::any_cast<const func_t &>(it->second).function;
         } catch (const std::bad_any_cast &) {
             throw std::logic_error(
                 "DLProblem: incorrect type for extra function \"" + name +