Add lazy evaluation, and introduce use-after-free

Signed-off-by: Slendi <slendi@socopon.com>

programs/dcfgq.c

@@ -105,39 +105,40 @@ int main(int argc, char **argv)
 	}
 
 	dcfg_Value *cur = evaled;
-	for (size_t i = 0; i < n; i++) {
+	for (size_t i = 0; i < n; ++i) {
 		Token *t = &toks[i];
 		dcfg_Value *next = NULL;
 
 		if (t->type == T_FIELD) {
 			if (!dcfg_Value_get_object_field_ex(cur, t->v.field, &next, true)) {
-				fprintf(stderr, "no such field\n");
-				dcfg_destroy(evaled);
-				dcfg_destroy(root);
-				dcfg_destroy_instance(inst);
-				return 1;
+				fputs("no such field\n", stderr);
+				goto fail;
 			}
 		} else {
 			if (!dcfg_Value_get_array_item_ex(cur, t->v.index, &next, true)) {
-				fprintf(stderr, "index out of bounds\n");
-				dcfg_destroy(evaled);
-				dcfg_destroy(root);
-				dcfg_destroy_instance(inst);
-				return 1;
+				fputs("index out of bounds\n", stderr);
+				goto fail;
 			}
 		}
 
-		if (cur != evaled)
+		if (cur != evaled) {
 			dcfg_destroy(cur);
-
+		}
 		cur = next;
 	}
 	print_value(cur);
-	if (cur != evaled)
+	if (cur != evaled) {
 		dcfg_destroy(cur);
+	}
 
 	dcfg_destroy(evaled);
 	dcfg_destroy(root);
 	dcfg_destroy_instance(inst);
 	return 0;
+
+fail:
+	dcfg_destroy(evaled);
+	dcfg_destroy(root);
+	dcfg_destroy_instance(inst);
+	return 1;
 }

src/dcfg.c

@@ -260,6 +260,7 @@ typedef struct {
 	StringView k;
 	Value *v;
 	bool key_allocated;
+	bool owned;
 } ValueObjectEntry;
 
 typedef struct {
@@ -268,6 +269,7 @@ typedef struct {
 
 typedef struct {
 	Value **valuev;
+	bool *ownedv;
 } ValueArray;
 
 typedef struct {
@@ -310,6 +312,8 @@ struct dcfg_Value {
 		ValueMemberAccess ma;
 		ValueFunctionCall c;
 	} v;
+
+	bool freed;
 };
 
 typedef struct Environment {
@@ -1355,6 +1359,7 @@ Value *ast_to_value(dcfg_Instance *instance, AST *root)
 	} else if (root->kind == ASTKind_Array) {
 		value->type = dcfg_ValueType_Array;
 		value->v.a.valuev = vector_create();
+		value->v.a.ownedv = vector_create();
 		for (size_t i = 0; i < vector_size(root->v.a.childv); i++) {
 			Value *v = ast_to_value(instance, root->v.a.childv[i]);
 			if (!v) {
@@ -1366,6 +1371,7 @@ Value *ast_to_value(dcfg_Instance *instance, AST *root)
 				return NULL;
 			}
 			vector_add(&value->v.a.valuev, Value *, v);
+			vector_add(&value->v.a.ownedv, bool, true);
 		}
 	} else if (root->kind == ASTKind_Function) {
 		value->type = dcfg_ValueType_Function;
@@ -1527,38 +1533,55 @@ void dcfg_destroy(dcfg_Value *value)
 	switch (value->type) {
 	case dcfg_ValueType_Object:
 		for (size_t i = 0; i < vector_size(value->v.o.entryv); i++) {
-			dcfg_destroy(value->v.o.entryv[i].v);
+			if (value->v.o.entryv[i].owned) {
+				dcfg_destroy(value->v.o.entryv[i].v);
+				value->v.o.entryv[i].v = NULL;
+			}
 			if (value->v.o.entryv[i].key_allocated) {
 				value->instance->free((void *)value->v.o.entryv[i].k.data);
+				value->v.o.entryv[i].k.data = NULL;
 			}
 		}
 		vector_free(value->v.o.entryv);
+		value->v.o.entryv = NULL;
 		break;
 
 	case dcfg_ValueType_Array:
 		for (size_t i = 0; i < vector_size(value->v.a.valuev); i++) {
-			dcfg_destroy(value->v.a.valuev[i]);
+			if (value->v.a.ownedv[i]) {
+				dcfg_destroy(value->v.a.valuev[i]);
+				value->v.a.valuev[i] = NULL;
+			}
 		}
 		vector_free(value->v.a.valuev);
+		value->v.a.valuev = NULL;
+		vector_free(value->v.a.ownedv);
+		value->v.a.ownedv = NULL;
 		break;
 
 	case dcfg_ValueType_Function:
 		if (!value->v.f.is_builtin) {
 			dcfg_destroy(value->v.f.v.f.body);
+			value->v.f.v.f.body = NULL;
 			vector_free(value->v.f.v.f.argv);
+			value->v.f.v.f.argv = NULL;
 		}
 		break;
 
 	case dcfg_ValueType_FunctionCall:
 		dcfg_destroy(value->v.c.function);
+		value->v.c.function = NULL;
 		for (size_t i = 0; i < vector_size(value->v.c.argv); i++) {
 			dcfg_destroy(value->v.c.argv[i]);
+			value->v.c.argv[i] = NULL;
 		}
 		vector_free(value->v.c.argv);
+		value->v.c.argv = NULL;
 		break;
 
 	case dcfg_ValueType_MemberAccess:
 		vector_free(value->v.ma.accessv);
+		value->v.ma.accessv = NULL;
 		break;
 
 	default:
@@ -1712,38 +1735,46 @@ dcfg_ValueType dcfg_Value_type_ex(dcfg_Value *value, bool evaluate)
 	return value->type;
 }
 
-bool dcfg_Value_get_object_field_ex(dcfg_Value *value, dcfg_StringView key,
-    dcfg_Value **out_value, bool evaluate)
+bool dcfg_Value_get_object_field_ex(
+    Value *obj, StringView key, Value **out, bool evaluate)
 {
-	if (!value || value->type != dcfg_ValueType_Object)
+	if (!obj || obj->type != dcfg_ValueType_Object)
 		return false;
 
-	ValueObject *obj = &value->v.o;
-	for (size_t i = 0; i < vector_size(obj->entryv); ++i) {
-		ValueObjectEntry *entry = &obj->entryv[i];
-		if (sv_eq(entry->k, key)) {
-			*out_value = entry->v;
-			if (evaluate)
-				dcfg_Value_evaluate(*out_value, out_value);
-			return true;
+	for (size_t i = 0; i < vector_size(obj->v.o.entryv); ++i) {
+		ValueObjectEntry *e = &obj->v.o.entryv[i];
+		if (!sv_eq(e->k, key))
+			continue;
+
+		*out = e->v;
+
+		if (evaluate) {
+			if (!dcfg_Value_evaluate(*out, out))
+				return false;
+			e->v = *out;
+			e->owned = true;
 		}
+		return true;
 	}
 	return false;
 }
 
 bool dcfg_Value_get_array_item_ex(
-    dcfg_Value *value, size_t index, dcfg_Value **out_value, bool evaluate)
+    Value *arr, size_t idx, Value **out, bool evaluate)
 {
-	if (!value || value->type != dcfg_ValueType_Array)
+	if (!arr || arr->type != dcfg_ValueType_Array)
+		return false;
+	if (idx >= vector_size(arr->v.a.valuev))
 		return false;
 
-	ValueArray *arr = &value->v.a;
-	if (index >= vector_size(arr->valuev))
-		return false;
+	*out = arr->v.a.valuev[idx];
 
-	*out_value = arr->valuev[index];
-	if (evaluate)
-		dcfg_Value_evaluate(*out_value, out_value);
+	if (evaluate) {
+		if (!dcfg_Value_evaluate(*out, out))
+			return false;
+		arr->v.a.valuev[idx] = *out;
+		arr->v.a.ownedv[idx] = true;
+	}
 	return true;
 }
 
@@ -1880,45 +1911,30 @@ bool dcfg_Value_evaluate_in_env(
 		v->type = dcfg_ValueType_Path;
 		v->v.p = value->v.p;
 	} else if (value->type == dcfg_ValueType_Object) {
+
 		v->type = dcfg_ValueType_Object;
 		v->v.o.entryv = vector_create();
-		for (size_t i = 0; i < vector_size(value->v.o.entryv); i++) {
+		for (size_t i = 0; i < vector_size(value->v.o.entryv); ++i) {
 			ValueObjectEntry *e = &value->v.o.entryv[i];
-			Value *new_v;
-			bool res = dcfg_Value_evaluate_in_env(e->v, frame, &new_v);
-			if (!res) {
-				ret = false;
-				break;
-			}
 			ValueObjectEntry ne = {
 				.k = e->k,
-				.v = new_v,
-				.key_allocated = true,
+				.v = e->v,
+				.key_allocated = false,
+				.owned = false,
 			};
-			ne.k.data = value->instance->alloc(ne.k.size + 1);
-			memcpy((void *)ne.k.data, e->k.data, ne.k.size);
-			((char *)ne.k.data)[ne.k.size] = '\0';
 			vector_add(&v->v.o.entryv, ValueObjectEntry, ne);
 		}
 	} else if (value->type == dcfg_ValueType_Array) {
 		v->type = dcfg_ValueType_Array;
 		v->v.a.valuev = vector_create();
-		for (size_t i = 0; i < vector_size(value->v.a.valuev); i++) {
-			Value *val = NULL;
-			bool res
-			    = dcfg_Value_evaluate_in_env(value->v.a.valuev[i], frame, &val);
-			if (!res) {
-				ret = false;
-			}
-			vector_add(&v->v.a.valuev, Value *, val);
+		v->v.a.ownedv = vector_create();
+		for (size_t i = 0; i < vector_size(value->v.a.valuev); ++i) {
+			vector_add(&v->v.a.valuev, Value *, value->v.a.valuev[i]);
+			vector_add(&v->v.a.ownedv[i], bool, false);
 		}
 	} else if (value->type == dcfg_ValueType_Function) {
-		Value *out_value_prev = *out_value;
-		bool res = dcfg_call_function(value, NULL, 0, out_value);
-		if (!res) {
-			dcfg_destroy(out_value_prev);
-			ret = false;
-		}
+		v->type = dcfg_ValueType_Function;
+		v->v.f = value->v.f;
 	} else if (value->type == dcfg_ValueType_MemberAccess) {
 		if (!frame) {
 			ret = false;
@@ -1934,21 +1950,9 @@ bool dcfg_Value_evaluate_in_env(
 			}
 		}
 	} else if (value->type == dcfg_ValueType_FunctionCall) {
-		Value *function;
-		bool res
-		    = dcfg_Value_evaluate_in_env(value->v.c.function, frame, &function);
-		if (!res || function->type != dcfg_ValueType_Function) {
-			ret = false;
-		} else {
-			Value *out_value_prev = *out_value;
-			bool res = dcfg_call_function(function, value->v.c.argv,
-			    vector_size(value->v.c.argv), out_value);
-			if (!res) {
-				ret = false;
-			} else {
-				dcfg_destroy(out_value_prev);
-			}
-		}
+		v->type = dcfg_ValueType_FunctionCall;
+		v->v.c.function = value->v.c.function;
+		v->v.c.argv = value->v.c.argv;
 	} else {
 		assert(0 && "Invalid value type");
 	}
@@ -2078,8 +2082,7 @@ bool dcfg_Value_evaluate_toplevel(dcfg_Value *top, dcfg_Value **out_value,
 
 	Value *argv[1] = { lib };
 	bool ok = dcfg_call_function(top, argv, 1, out_value);
-	vector_free(lib->v.o.entryv);
-	inst->free(lib);
+	dcfg_destroy(lib);
 	return ok;
 }