lang: Create modules and dependencies on request

lang/main.c

@@ -62,6 +62,7 @@ int lang_main(void) {
 	VmState state = vm_create();
 	test_rational(state);
 	test_module(state);
+	modules_free(state);
 	vm_destroy(&state);
 	printf("All done!\n");
 	return 0;

lang/module.c

@@ -23,6 +23,30 @@ static ModuleInfo *modules_list[] = {
 };
 #undef X
 
+// Size of a stack in elemenets
+#define STACK_SIZE 64
+
+// A stack of ModuleInfo pointers
+struct module_stack {
+	const ModuleInfo *elems[STACK_SIZE];
+	int next;
+};
+
+// A stack of Objects
+struct object_stack {
+	Object elems[STACK_SIZE];
+	int next;
+};
+
+// A mapping mapping between ModuleInfo and Object
+// Each stack element should have a corresponding element
+// in the other stack at the same index
+struct module_mapping {
+	struct module_stack infos;
+	struct object_stack objects;
+};
+
+// Finds a ModuleInfo by name
 static const ModuleInfo *info_by_name(const char *name) {
 	for (unsigned int i = 0; i < ARRAY_SIZE(modules_list); ++i) {
 		ModuleInfo *info = modules_list[i];
@@ -32,12 +56,7 @@ static const ModuleInfo *info_by_name(const char *name) {
 	return NULL;
 }
 
-struct module_stack {
-	ModuleInfo *elems[64];
-	int next;
-};
-
-// Checks if an info is in a stack
+// Checks if a ModuleInfo is in a module_stack
 static int in_stack(const ModuleInfo *info, struct module_stack *stack) {
 	for (int i = 0; i < stack->next; ++i) {
 		ModuleInfo *elem = stack->elems[i];
@@ -48,8 +67,8 @@ static int in_stack(const ModuleInfo *info, struct module_stack *stack) {
 }
 
 // Traverses a module use dependency tree, checking for circular dependencies
-// This uses a depth-first search with a stack for traversing
-// The resulting visited list is the reverse load order
+// The result is the visited stack containing modules in load order
+// This function works using a depth-first search
 static void traverse_module_uses(
 	const ModuleInfo *start, struct module_stack *visited) {
 	static struct module_stack traversing = {0};
@@ -57,37 +76,86 @@ static void traverse_module_uses(
 		abort_print("Modules too big to traverse");
 	if (in_stack(start, visited))
 		return;
+	// Push the start module to the top of the traversal stack
 	traversing.next = 0;
 	traversing.elems[traversing.next++] = start;
 	do {
+		// Use the top of traversal stack as our current module
 		ModuleInfo *cur = traversing.elems[traversing.next - 1];
+		// Iterate through module uses
 		const char **use = cur->uses;
 		while (*use) {
+			// Find the info associated with the use
 			const ModuleInfo *info = info_by_name(*use);
 			if (info == NULL)
 				abort_print("Couldn't find module");
+			// If we are already traversing this use then
+			// we have a cyclic dependency. Bail
 			if (in_stack(info, &traversing))
 				abort_print("Cyclic dependency found");
+			// If this use is unvisited, push it to the stack
+			// and traverse it
 			if (!in_stack(info, visited)) {
 				traversing.elems[traversing.next++] = info;
 				break;
 			}
 			use++;
 		}
+		// No unvisited uses? Mark this module as visited and
+		// retry the module we were traversing before
 		if (*use == NULL) {
 			traversing.elems[traversing.next--] = NULL;
 			visited->elems[visited->next++] = cur;
 		}
-	} while (traversing.next != -1);
+	} while (traversing.next != 0);
+
+	// The traversal stack is now empty, all done!
 }
 
+// Finds a module object by its info using a module_mapping
+Object get_module_by_info(
+	struct module_mapping *mapping, const ModuleInfo *info) {
+	struct module_stack *infos = &mapping->infos;
+	for (int i = 0; i < infos->next; ++i) {
+		ModuleInfo *elem = infos->elems[i];
+		if (elem == info)
+			return mapping->objects.elems[i];
+	}
+	abort_print("Couldn't find module by info");
+}
+
+// Creates modules and stores them in a mapping
+void create_modules(VmState state, struct module_mapping *mapping) {
+	struct module_stack *infos = &mapping->infos;
+	struct object_stack *objs = &mapping->objects;
+	for (int i = objs->next; i < infos->next; ++i) {
+		ModuleInfo *info = infos->elems[i];
+		Object module = info->create(state);
+		objs->elems[objs->next++] = module;
+	}
+}
+
+// Global mapping used for finding and freeing modules
+static struct module_mapping mapping = {0};
+
 Object module_find(VmState state, const char *name) {
 	const ModuleInfo *info = info_by_name(name);
 	vm_abort_if(state, !info, "Unable to find module!");
-	static struct module_stack visited = {0};
-	if (sizeof(modules_list) > sizeof(visited.elems))
+	if (sizeof(modules_list) > sizeof(mapping.infos.elems))
 		abort_print("Modules too big to track");
-	traverse_module_uses(info, &visited); // TODO: Does nothing
-	traverse_module_uses(info, &visited); // TODO: Does nothing
-	return info->create(state);
+	if (sizeof(modules_list) > sizeof(mapping.objects.elems))
+		abort_print("Modules too big to load");
+	traverse_module_uses(info, &mapping.infos);
+	create_modules(state, &mapping);
+	Object module = get_module_by_info(&mapping, info);
+	// Create a new reference for the caller
+	object_hold(state, module);
+	return module;
+}
+
+void modules_free(VmState state) {
+	struct object_stack *objs = &mapping.objects;
+	for (int i = 0; i < objs->next; ++i)
+		object_drop(state, &objs->elems[i]);
+	memset(&mapping, 0, sizeof(mapping));
 }

lang/module.h

@@ -7,11 +7,16 @@
 #include "types.h"
 
 // Finds a module by its name
+// This internally loads the module and dependencies
+// A new reference is created for the caller
 Object module_find(VmState state, const char *name);
 
+// Frees all modules loaded internally
+// You must call this at the end of your program
+void modules_free(VmState state);
+
 // The following section is an internal API for use only with
 // the compiler's C code generator. Do not use for regular C code.
-
 #ifdef MODULE_INTERNAL_API
 
 // Data structure for creating a module