From ad659dca44892a5f2ba4e088603a819af58a5819 Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Wed, 27 Oct 2021 13:59:25 +0200
Subject: Add support for lexically scoped local variables

---
 src/bytecode/vm.h | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

(limited to 'src/bytecode/vm.h')

diff --git a/src/bytecode/vm.h b/src/bytecode/vm.h
index 84d2432..287c83c 100755
--- a/src/bytecode/vm.h
+++ b/src/bytecode/vm.h
@@ -188,6 +188,13 @@ vm_interpret(VM *vm) {
                 ssize_t idx = AS_FIXNUM(array_pop(vm->stack));
                 vm->stack[frame->stack_offset + idx] = value;
             } break;
+            case OP_SET_LOCAL: {
+                Object value = array_pop(vm->stack);
+                ssize_t idx = AS_FIXNUM(array_pop(vm->stack));
+                ssize_t depth = AS_FIXNUM(array_pop(vm->stack));
+                CallFrame frame = vm->frames[depth];
+                vm->stack[frame.stack_offset + idx] = value;
+            } break;
             case OP_DEF: {
                 Object value = array_pop(vm->stack);
                 Object name = array_pop(vm->stack);
@@ -280,13 +287,13 @@ vm_interpret(VM *vm) {
                 // Check the number of arguments is correct.
                 // NOTE: This is probably better handled at compilation, but for
                 // now this is simpler to implement.
-                ssize_t n_params = array_size(proc.chunk->params);
+                ssize_t n_params = proc.chunk->n_params;
+                ssize_t n_locals = proc.chunk->n_locals;
                 if (n_args < n_params) {
                     RUNTIME_ERROR(ERR_NOT_ENOUGH_ARGS);
                 } else if (n_args > n_params) {
                     RUNTIME_ERROR(ERR_TOO_MANY_ARGS);
                 }
-                ssize_t n_locals = array_size(proc.chunk->locals) - n_params;
 
 #ifdef DEBUG
                 disassemble_chunk(proc.chunk);
@@ -298,7 +305,7 @@ vm_interpret(VM *vm) {
                     CallFrame new_frame = (CallFrame){
                         .chunk = proc.chunk,
                         .rp = vm->pc,
-                        .stack_offset = array_size(vm->stack) - array_size(proc.chunk->params),
+                        .stack_offset = array_size(vm->stack) - n_params,
                     };
                     array_push(vm->frames, new_frame);
                     frame = &vm->frames[array_size(vm->frames) - 1];
@@ -315,7 +322,8 @@ vm_interpret(VM *vm) {
                     }
 
                     // Reset stack size.
-                    array_head(vm->stack)->size = frame->stack_offset + n_params + n_locals;
+                    size_t offset = frame->stack_offset + n_params + n_locals;
+                    array_head(vm->stack)->size = offset;
                 }
                 vm->pc = frame->chunk->code;
             } break;
-- 
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