Generate shared object

Modify build-script to generate a shared library for Godot.

src/Makefile.am

@@ -3,9 +3,13 @@
 #bin_PROGRAMS = $(top_builddir)/bin/rtr # Program name.
 #__top_builddir__bin_rtr_CFLAGS = -DBUILD # Define BUILD variable.
 #__top_builddir__bin_rtr_SOURCES = main.c # Sources
-bin_PROGRAMS = rtr
-rtr_CFLAGS = -DBUILD -c -fPIC # Define BUILD variable.
-rtr_SOURCES = main.c # Sources
+lib_LTLIBRARIES = librtr.la
+librtr_la_SOURCES = main.c
+librtr_la_LDFLAGS = -module -avoid-version -export-dynamic
+
+#bin_PROGRAMS = rtr
+#rtr_CFLAGS = -DBUILD -c -fPIC -shared # Define BUILD and output shared.
+#rtr_SOURCES = main.c # Sources
 #if extra
 #__top_builddir__bin_rtr_LDADD = ./extra/libextra.la # Include extra.
 

src/main.c

@@ -18,3 +18,116 @@ int main()
     return(0);
 }
 */
+
+typedef struct {
+    uint8_t godot_data_dont_touch_this[sizeof(void *)];
+} String;
+
+typedef struct {
+    uint8_t godot_data_dont_touch_this[sizeof(void *)];
+} StringName;
+
+typedef struct {
+    uint8_t godot_data_dont_touch_this[24];
+} Variant;
+
+// GDExtension interface function pointers
+static GDExtensionInterfaceStringNewWithUtf8Chars string_new_with_utf8_chars;
+static GDExtensionInterfaceVariantGetPtrConstructor variant_get_ptr_constructor;
+static GDExtensionInterfaceVariantGetPtrDestructor variant_get_ptr_destructor;
+static GDExtensionInterfaceGetVariantFromTypeConstructor get_variant_from_type_constructor;
+static GDExtensionInterfaceVariantGetPtrUtilityFunction variant_get_ptr_utility_function;
+static GDExtensionInterfaceVariantDestroy variant_destroy;
+// Godot API function pointers
+static GDExtensionPtrConstructor construct_StringName_from_String;
+static GDExtensionVariantFromTypeConstructorFunc construct_Variant_from_String;
+static GDExtensionPtrDestructor destroy_String;
+static GDExtensionPtrDestructor destroy_StringName;
+
+// here is our global "print" StringName
+static StringName print_StringName;
+// and here is our global "print" function
+static GDExtensionPtrUtilityFunction print_function;
+
+StringName construct_StringName_from_cstring(const char *text) {
+    // 1. Construct a String from the C string
+    String string;
+    string_new_with_utf8_chars(&string, text);
+
+    // 2. Construct a StringName from the String
+    StringName string_name;
+    GDExtensionConstTypePtr constructor_arguments[1] = { &string };
+    construct_StringName_from_String(&string_name, constructor_arguments);
+
+    // 3. Destroy the String, since it's not needed anymore
+    destroy_String(&string);
+
+    return string_name;
+}
+
+void print(const char *text) {
+    // 1. Construct a String from the C string
+    String string;
+    string_new_with_utf8_chars(&string, text);
+
+    // 2. Construct a Variant from the String
+    Variant arg1;
+    construct_Variant_from_String(&arg1, &string);
+
+    // 3. Call the utility function
+    // Since it's a void function, use "NULL" for the return pointer
+    GDExtensionConstVariantPtr args[1] = { &arg1 };
+    print_function(NULL, args, 1);
+
+    // 4. Clean up resources that are no longer needed
+    variant_destroy(&arg1);
+    destroy_String(&string);
+}
+
+void initialize(void *userdata, GDExtensionInitializationLevel p_level) {
+    if (p_level != GDEXTENSION_INITIALIZATION_SCENE) {
+        return;
+    }
+
+    // StringName constructor at index 2 is the one that receives String
+    // You can find this information in `extension_api.json` file
+    construct_StringName_from_String = variant_get_ptr_constructor(GDEXTENSION_VARIANT_TYPE_STRING_NAME, 2);
+    construct_Variant_from_String = get_variant_from_type_constructor(GDEXTENSION_VARIANT_TYPE_STRING);
+    destroy_String = variant_get_ptr_destructor(GDEXTENSION_VARIANT_TYPE_STRING);
+    destroy_StringName = variant_get_ptr_destructor(GDEXTENSION_VARIANT_TYPE_STRING_NAME);
+
+    // Initialize "print" StringName
+    print_StringName = construct_StringName_from_cstring("print");
+    // then fetch the "print" function pointer
+    print_function = variant_get_ptr_utility_function(&print_StringName, 2648703342);
+
+    print("Hello GDExtension from C!");
+}
+
+void deinitialize(void *userdata, GDExtensionInitializationLevel p_level) {
+    if (p_level != GDEXTENSION_INITIALIZATION_SCENE) {
+        return;
+    }
+
+    print("Goodbye GDExtension from C!");
+
+    // Destroy "print" StringName
+    destroy_StringName(&print_StringName);
+}
+
+GDExtensionBool hello_extension_entry(
+    GDExtensionInterfaceGetProcAddress p_get_proc_address,
+    GDExtensionClassLibraryPtr p_library,
+    GDExtensionInitialization *r_initialization
+) {
+    r_initialization->initialize = &initialize;
+    r_initialization->deinitialize = &deinitialize;
+    // save the GDExtension API function pointers globally
+    string_new_with_utf8_chars = (GDExtensionInterfaceStringNewWithUtf8Chars) p_get_proc_address("string_new_with_utf8_chars");
+    variant_get_ptr_constructor = (GDExtensionInterfaceVariantGetPtrConstructor) p_get_proc_address("variant_get_ptr_constructor");
+    variant_get_ptr_destructor = (GDExtensionInterfaceVariantGetPtrDestructor) p_get_proc_address("variant_get_ptr_destructor");
+    get_variant_from_type_constructor = (GDExtensionInterfaceGetVariantFromTypeConstructor) p_get_proc_address("get_variant_from_type_constructor");
+    variant_get_ptr_utility_function = (GDExtensionInterfaceVariantGetPtrUtilityFunction) p_get_proc_address("variant_get_ptr_utility_function");
+    variant_destroy = (GDExtensionInterfaceVariantDestroy) p_get_proc_address("variant_destroy");
+    return 1;
+}

src/main.gdextension

@@ -1,8 +0,0 @@
-[configuration]
-entry_symbol = "main_extension_entry"
-compatibility_minimum = "4.2"
-
-[libraries]
-windows.x86_64 = "main-gdextension.dll"
-macos = "libmain-gdextension.dylib"
-linux.x86_64 = "libhello-gdextension.so"