Fix windows side of dll loading code

source/reflect_load_metafunction.h

@@ -5,37 +5,36 @@
 #include <utility>
 #include "cpp2util.h"
 
-#ifdef _MSC_VER
-#define WIN32_LEAN_AND_MEAN
-#include <windows.h>
+#ifdef _WIN32
+#include <libloaderapi.h>
 #else
 #include <dlfcn.h>
-#endif // _MSC_VER
+#endif // _WIN32
 
 namespace cpp2::meta {
 
 class dll
 {
 public:
-    dll(std::string_view path)
+    dll(std::string const& path)
     {
-#ifdef _MSC_VER
-        handle_ = static_cast<void*>(LoadLibraryA(path.data()));
+#ifdef _WIN32
+        handle_ = static_cast<void*>(LoadLibraryA(path.c_str()));
 #else
-        handle_ = static_cast<void*>(dlopen(path.data(), RTLD_NOW|RTLD_LOCAL));
-#endif // _MSC_VER
+        handle_ = static_cast<void*>(dlopen(path.c_str(), RTLD_NOW|RTLD_LOCAL));
+#endif // _WIN32
         // TODO: log if the dll could not be open?
     }
 
     ~dll() noexcept
     {
         if(handle_ == nullptr);
             return;
-#ifdef _MSC_VER
-        FreeLibrary(static_cast<HMODULE>(handle));
+#ifdef _WIN32
+        FreeLibrary(static_cast<HMODULE>(handle_));
 #else
         dlclose(handle_);
-#endif // _MSC_VER
+#endif // _WIN32
     }
 
     // Uncopyable
@@ -60,25 +59,31 @@ class dll
     auto is_open() noexcept -> bool { return handle_ != nullptr; }
 
     template<typename T>
-    auto get_alias(std::string_view name) noexcept -> T*
+    auto get_alias(std::string const& name) noexcept -> T*
     {
-        void* symbol = nullptr;
-#ifdef _MSC_VER
-        symbol = static_cast<void*>(GetProcAddress(static_cast<HMODULE>(handle_), name.data()));
+#ifdef _WIN32
+        auto symbol = GetProcAddress(static_cast<HMODULE>(handle_), name.c_str());
 #else
-        symbol = dlsym(handle_, name.data());
+        auto symbol = dlsym(handle_, name.c_str());
         if(symbol == nullptr)
         {
             // Some platforms export with additional underscore, so try that.
-            auto const us_name = std::string("_") + name.data();
+            auto const us_name = "_" + name;
             symbol = dlsym(handle_, us_name.c_str());
         }
-#endif // _MSC_VER
+#endif // _WIN32
         // TODO: log if the symbol is not found?
-        return reinterpret_cast<T*>(symbol);
+        return function_cast<T*>(symbol);
     }
 private:
     void* handle_{nullptr};
+
+    template<typename T>
+    static T function_cast(auto ptr) {
+        using generic_function_ptr = void (*)(void);
+        return reinterpret_cast<T>(reinterpret_cast<generic_function_ptr>(ptr));
+    }
+
 };
 
 
@@ -89,6 +94,10 @@ class dll
 //  'CPPFRONT_METAFUNCTION_LIBRARIES'
 auto load_metafunction(std::string const& name) -> std::function<void(type_declaration&)>
 {
+    // FIXME: On Windows, using this approach with the system apis not set to utf8, will
+    // break if a metafunction library contains unicode codepoints in its name, a proper
+    // way to handle this would be to use _wgetenv and use wchar_t strings for the dll opening
+    // function
     auto cpp1_libraries_cstr = std::getenv("CPPFRONT_METAFUNCTION_LIBRARIES");
     if (!cpp1_libraries_cstr) {
         return {};
@@ -103,7 +112,7 @@ auto load_metafunction(std::string const& name) -> std::function<void(type_decla
         auto lib_path = cpp1_libraries.substr(0, colon);
         cpp1_libraries.remove_prefix(lib_path.size() + unsigned(colon != lib_path.npos));
 
-        auto lib = std::make_shared<dll>(lib_path);
+        auto lib = std::make_shared<dll>(std::string(lib_path));
         if(!lib->is_open())
             continue;