store stack base pointer in the stack frame

include/lang2/bytecode.h

@@ -78,8 +78,10 @@ enum l2_opcode {
 
 	/*
 	 * Return from a function.
+	 * Pop <retval>
 	 * FSPop
-	 * Pop (discard args array)
+	 * Reset stack pointer to <stack base>
+	 * Push <retval>
 	 * Jump to <return address>
 	 */
 	L2_OP_RET,

include/lang2/vm/vm.h

@@ -77,6 +77,7 @@ struct l2_vm_namespace {
 
 struct l2_vm_stack_frame {
 	l2_word ns;
+	l2_word sptr;
 	l2_word retptr;
 };
 

lib/vm/print.c

@@ -101,7 +101,8 @@ void l2_vm_print_stack(struct l2_vm *vm) {
 
 void l2_vm_print_fstack(struct l2_vm *vm) {
 	for (l2_word i = 0; i < vm->fsptr; ++i) {
-		printf("  %i: %i, ret %i\n", i, vm->fstack[i].ns, vm->fstack[i].retptr);
+		printf("  %i: %i, ret %i, stack base %i\n",
+				i, vm->fstack[i].ns, vm->fstack[i].retptr, vm->fstack[i].sptr);
 	}
 }
 

lib/vm/vm.c

@@ -261,6 +261,8 @@ void l2_vm_step(struct l2_vm *vm) {
 			l2_word func_id = vm->stack[--vm->sptr];
 			struct l2_vm_value *func = &vm->values[func_id];
 
+			l2_word stack_base = vm->sptr;
+
 			enum l2_value_type typ = l2_vm_value_type(func);
 
 			// C functions are called differently from language functions
@@ -284,6 +286,7 @@ void l2_vm_step(struct l2_vm *vm) {
 			vm->values[ns_id].flags = L2_VAL_TYPE_NAMESPACE;
 			vm->fstack[vm->fsptr].ns = ns_id;
 			vm->fstack[vm->fsptr].retptr = vm->iptr;
+			vm->fstack[vm->fsptr].sptr = stack_base;
 			vm->fsptr += 1;
 
 			vm->iptr = func->func.pos;
@@ -323,8 +326,10 @@ void l2_vm_step(struct l2_vm *vm) {
 	case L2_OP_RET:
 		{
 			l2_word retval = vm->stack[--vm->sptr];
-			vm->sptr -= 1; // Discard arguments array
-			l2_word retptr = vm->fstack[--vm->fsptr].retptr;
+			l2_word retptr = vm->fstack[vm->fsptr - 1].retptr;
+			l2_word sptr = vm->fstack[vm->fsptr - 1].sptr;
+			vm->fsptr -= 1;
+			vm->sptr = sptr;
 			vm->stack[vm->sptr++] = retval;
 			vm->iptr = retptr;
 		}

test/src/eval.t.c

@@ -13,7 +13,7 @@ static struct l2_vm vm;
 
 static struct l2_vm_value *var_lookup(const char *name) {
 	l2_word atom_id = l2_strset_get(&gen.atomset, name);
-	l2_word id = l2_vm_namespace_get(&vm, &vm.values[vm.fstack[1].namespace], atom_id);
+	l2_word id = l2_vm_namespace_get(&vm, &vm.values[vm.fstack[1].ns], atom_id);
 	return &vm.values[id];
 }