feat: implement simple infinite loop checker

src/compiler/checkers/fzl_loop_check.c

@@ -6,42 +6,214 @@
 #include <compiler/utils/fzl_symtable.h>
 #include <stdbool.h>
 #include <stdint.h>
+#include <string.h>
+
+ssize_t check_top;
+fzl_nodetype_t check_tree[256];
+
+void ghost_walk_changed(fzl_node_t *node, bool *changed, fzl_sym_t *sym)
+{
+  if (!node || !changed || *changed)
+    return;
+
+  check_tree[check_top++] = node->type;
+
+  switch (node->type)
+  {
+    case FZL_NODETYPE_DECLARATION:
+    case FZL_NODETYPE_CONSTRUCT:
+    case FZL_NODETYPE_CLASS:
+    case FZL_NODETYPE_FUNCTION:
+    case FZL_NODETYPE_LITERAL:
+      break;
+
+    case FZL_NODETYPE_UNARY_PLUS:
+    case FZL_NODETYPE_UNARY_MINUS:
+    case FZL_NODETYPE_NOT:
+      ghost_walk_changed(node->unary_op.operand, changed, sym);
+      break;
+
+    case FZL_NODETYPE_ADD:
+    case FZL_NODETYPE_SUB:
+    case FZL_NODETYPE_MUL:
+    case FZL_NODETYPE_DIV:
+    case FZL_NODETYPE_POW:
+    case FZL_NODETYPE_MOD:
+    case FZL_NODETYPE_OR:
+    case FZL_NODETYPE_AND:
+    case FZL_NODETYPE_EQUAL:
+    case FZL_NODETYPE_NEQUAL:
+    case FZL_NODETYPE_LESS:
+    case FZL_NODETYPE_LESS_EQUAL:
+    case FZL_NODETYPE_GREATER:
+    case FZL_NODETYPE_GREATER_EQUAL:
+    case FZL_NODETYPE_ASSIGN:
+      ghost_walk_changed(node->binary_op.left, changed, sym);
+      ghost_walk_changed(node->binary_op.right, changed, sym);
+      break;
+
+    case FZL_NODETYPE_FIELD:
+      ghost_walk_changed(node->memb.parent, changed, sym);
+      ghost_walk_changed(node->memb.field, changed, sym);
+      break;
+
+    case FZL_NODETYPE_RETURN:
+      ghost_walk_changed(node->ret.value, changed, sym);
+      break;
+
+    case FZL_NODETYPE_CONDITIONAL:
+      ghost_walk_changed(node->cond.condition, changed, sym);
+      ghost_walk_changed(node->cond.true_block, changed, sym);
+      ghost_walk_changed(node->cond.else_block, changed, sym);
+      break;
+
+    case FZL_NODETYPE_LOOP:
+      ghost_walk_changed(node->loop.cond, changed, sym);
+      ghost_walk_changed(node->loop.step, changed, sym);
+      ghost_walk_changed(node->loop.body, changed, sym);
+      break;
+
+    case FZL_NODETYPE_BLOCK:
+      for (size_t i = 0; i < node->list.entry_count; i++)
+        ghost_walk_changed(node->list.entries[i], changed, sym);
+      break;
+
+    case FZL_NODETYPE_CALL:
+      ghost_walk_changed(node->call.callee, changed, sym);
+      for (size_t i = 0; i < node->call.args_count; i++)
+        ghost_walk_changed(node->call.args[i], changed, sym);
+      break;
+
+    case FZL_NODETYPE_IDENTIFIER:
+      if (strcmp(node->token->value, sym->name) == 0)
+      {
+        *changed = true;
+      }
+
+      if (*changed)
+      {
+        *changed = false;
+        for (ssize_t i = check_top - 1; i >= 0; i--)
+        {
+          fzl_nodetype_t cur_t = check_tree[i];
+          if (cur_t == FZL_NODETYPE_ADD || cur_t == FZL_NODETYPE_SUB ||
+              cur_t == FZL_NODETYPE_MUL || cur_t == FZL_NODETYPE_DIV ||
+              cur_t == FZL_NODETYPE_POW || cur_t == FZL_NODETYPE_MOD ||
+              cur_t == FZL_NODETYPE_UNARY_MINUS)
+          {
+            *changed = true;
+            break;
+          }
+        }
+      }
+      break;
+  }
+
+  check_tree[--check_top] = 0;
+}
+
+// Whether value changed in loop body
+bool value_is_changed(fzl_node_t *node, fzl_sym_t *sym)
+{
+  if (!node || !sym)
+    return false;
+
+  bool changed = false;
+  check_top    = 0;
+  memset(check_tree, 0, sizeof(check_tree));
+  ghost_walk_changed(node, &changed, sym);
+
+  return changed;
+}
+
+// Try to find symbol in loop condition node
+bool retrieve_cond_sym(fzl_walker_t *walker, fzl_node_t *node, fzl_sym_t *sym)
+{
+  if (!walker || !node)
+    return false;
+
+  switch (node->type)
+  {
+    case FZL_NODETYPE_BLOCK:
+    case FZL_NODETYPE_CALL:
+    case FZL_NODETYPE_LITERAL:
+    case FZL_NODETYPE_CONDITIONAL:
+    case FZL_NODETYPE_FUNCTION:
+    case FZL_NODETYPE_RETURN:
+    case FZL_NODETYPE_CLASS:
+    case FZL_NODETYPE_FIELD:
+    case FZL_NODETYPE_CONSTRUCT:
+    case FZL_NODETYPE_LOOP:
+    case FZL_NODETYPE_ASSIGN:
+    case FZL_NODETYPE_DECLARATION:
+      return false;
+
+    case FZL_NODETYPE_UNARY_MINUS:
+    case FZL_NODETYPE_UNARY_PLUS:
+    case FZL_NODETYPE_NOT:
+      return retrieve_cond_sym(walker, node->unary_op.operand, sym);
+
+    case FZL_NODETYPE_ADD:
+    case FZL_NODETYPE_SUB:
+    case FZL_NODETYPE_MUL:
+    case FZL_NODETYPE_DIV:
+    case FZL_NODETYPE_POW:
+    case FZL_NODETYPE_MOD:
+    case FZL_NODETYPE_AND:
+    case FZL_NODETYPE_OR:
+    case FZL_NODETYPE_LESS:
+    case FZL_NODETYPE_LESS_EQUAL:
+    case FZL_NODETYPE_GREATER:
+    case FZL_NODETYPE_GREATER_EQUAL:
+    case FZL_NODETYPE_EQUAL:
+    case FZL_NODETYPE_NEQUAL:
+      if (retrieve_cond_sym(walker, node->binary_op.left, sym))
+        return true;
+      if (retrieve_cond_sym(walker, node->binary_op.right, sym))
+        return true;
+      return false;
+
+    case FZL_NODETYPE_IDENTIFIER:
+    {
+      bool exists;
+      for (ssize_t i = walker->sym_top - 1; i >= 0; i--)
+      {
+        if ((exists = fzl_symt_get(walker->syms[i], (char *)node->token->value,
+                                   sym)))
+          break;
+      }
+      return exists;
+    }
+  }
+
+  return false;
+}
 
 // Check for infinite loop
-bool is_infinite_loop(fzl_walker_t *walker, size_t start_ip, size_t end_ip)
+bool is_infinite_loop(fzl_walker_t *walker, fzl_node_t *node, size_t start_ip,
+                      size_t end_ip)
 {
   if (!walker)
     return false;
 
   end_ip = (end_ip >= walker->op_count) ? (walker->op_count - 1) : end_ip;
 
-  // Can we determine an init block?
-  size_t maybe_init_start = start_ip + 1;
-  size_t maybe_init_end   = start_ip + 6;
-  fzl_const_t *declared   = NULL;
-  for (size_t i = maybe_init_start; i <= maybe_init_end; i++)
-  {
-    if (walker->ops[i] != FZL_OPCODE_STORE)
-      continue;
-
-    declared = &walker->consts->array[walker->ops[i - 1]];
-    break;
-  }
-
-  if (declared)
-  {
   fzl_sym_t sym;
-    bool found = false;
+  bool sym_exists = retrieve_cond_sym(walker, node->loop.cond, &sym);
-    for (ssize_t i = walker->sym_top - 1; i >= 0; i--)
+  if (sym_exists)
-      if ((found = fzl_symt_get(walker->syms[i],
+  {
-                                (char *)declared->as.string.chars, &sym)))
+    // fzl_sym_t sym;
-        break;
+    // bool found = false;
-
+    // for (ssize_t i = walker->sym_top - 1; i >= 0; i--)
-    if (!found)
+    //   if ((found = fzl_symt_get(walker->syms[i],
-      return false; // suspicious
+    //                             (char *)declared->as.string.chars, &sym)))
+    //     break;
 
     if (sym.type >= FZL_TYPE_INT8)
     {
+      bool value_changed = value_is_changed(node, &sym);
+      if (value_changed)
+        return false;
     }
   }
 

src/compiler/fzl_walker.c

@@ -14,7 +14,8 @@
 #include <stdlib.h>
 #include <string.h>
 
-extern bool is_infinite_loop(fzl_walker_t *walker, size_t ls, size_t le);
+extern bool is_infinite_loop(fzl_walker_t *walker, fzl_node_t *node, size_t ls,
+                             size_t le);
 
 char *null_name = "<null>";
 char wlast_err[256];
@@ -221,6 +222,7 @@ fzl_walk_res_t walk(fzl_walker_t *walker, fzl_node_t *node)
 
         push_op(walker, FZL_OPCODE_MK_ENVTABLE);
         walker->syms[walker->sym_top++] = fzl_mksymt();
+        size_t loop_begin_ip            = walker->op_count;
 
         if (node->loop.init)
         {
@@ -274,9 +276,10 @@ fzl_walk_res_t walk(fzl_walker_t *walker, fzl_node_t *node)
         push_op(walker, FZL_OPCODE_RM_ENVTABLE);
 
         bool is_infinite =
-            is_infinite_loop(walker, start_ip, walker->op_count - 2);
+            is_infinite_loop(walker, node, loop_begin_ip, walker->op_count - 2);
         if (is_infinite)
         {
+          free(newctx->breaks);
           snprintf(wlast_err, sizeof(wlast_err),
                    "'%s': infinite loop detected at %ld:%ld",
                    node->token->filename, node->token->ln, node->token->cn);

tests/programs/neg_infinite_for.fzs

@@ -1,3 +1,3 @@
-for (int i = 0; i < 5; i = i - 1)
+for (int i = 0; i < 5; i = i + 0)
 {}