Handle block scope

parse.c

@@ -18,11 +18,26 @@
 
 #include "chibicc.h"
 
+// Scope for local or global variables.
+typedef struct VarScope VarScope;
+struct VarScope {
+  VarScope *next;
+  char *name;
+  int depth;
+  Var *var;
+};
+
 // All local variable instances created during parsing are
 // accumulated to this list.
 static Var *locals;
 static Var *globals;
 
+static VarScope *var_scope;
+
+// scope_depth is incremented by one at the beginning of a block
+// scope and decremented by one at the end of a block scope.
+static int scope_depth;
+
 static Type *typespec(Token **rest, Token *tok);
 static Type *declarator(Token **rest, Token *tok, Type *ty);
 static Node *declaration(Token **rest, Token *tok);
@@ -39,16 +54,21 @@ static Node *postfix(Token **rest, Token *tok);
 static Node *unary(Token **rest, Token *tok);
 static Node *primary(Token **rest, Token *tok);
 
-// Find a local variable by name.
+static void enter_scope(void) {
+  scope_depth++;
+}
+
+static void leave_scope(void) {
+  scope_depth--;
+  while (var_scope && var_scope->depth > scope_depth)
+    var_scope = var_scope->next;
+}
+
+// Find a variable by name.
 static Var *find_var(Token *tok) {
-  for (Var *var = locals; var; var = var->next)
-    if (strlen(var->name) == tok->len && !strncmp(tok->loc, var->name, tok->len))
-      return var;
-
-  for (Var *var = globals; var; var = var->next)
-    if (strlen(var->name) == tok->len && !strncmp(tok->loc, var->name, tok->len))
-      return var;
-
+  for (VarScope *sc = var_scope; sc; sc = sc->next)
+    if (equal(tok, sc->name))
+      return sc->var;
   return NULL;
 }
 
@@ -84,10 +104,22 @@ static Node *new_var_node(Var *var, Token *tok) {
   return node;
 }
 
+static VarScope *push_scope(char *name, Var *var) {
+  VarScope *sc = calloc(1, sizeof(VarScope));
+  sc->name = name;
+  sc->var = var;
+  sc->depth = scope_depth;
+
+  sc->next = var_scope;
+  var_scope = sc;
+  return sc;
+}
+
 static Var *new_var(char *name, Type *ty) {
   Var *var = calloc(1, sizeof(Var));
   var->name = name;
   var->ty = ty;
+  push_scope(name, var);
   return var;
 }
 
@@ -293,9 +325,11 @@ static Node *stmt(Token **rest, Token *tok) {
 // compound-stmt = (declaration | stmt)* "}"
 static Node *compound_stmt(Token **rest, Token *tok) {
   Node *node = new_node(ND_BLOCK, tok);
-
   Node head = {};
   Node *cur = &head;
+
+  enter_scope();
+
   while (!equal(tok, "}")) {
     if (is_typename(tok))
       cur = cur->next = declaration(&tok, tok);
@@ -304,6 +338,8 @@ static Node *compound_stmt(Token **rest, Token *tok) {
     add_type(cur);
   }
 
+  leave_scope();
+
   node->body = head.next;
   *rest = tok->next;
   return node;
@@ -616,12 +652,14 @@ static Token *function(Token *tok, Type *basety) {
   fn->is_function = true;
 
   locals = NULL;
+  enter_scope();
   create_param_lvars(ty->params);
   fn->params = locals;
 
   tok = skip(tok, "{");
   fn->body = compound_stmt(&tok, tok);
   fn->locals = locals;
+  leave_scope();
   return tok;
 }
 

test.sh

@@ -216,4 +216,8 @@ assert 2 'int main() { /* return 1; */ return 2; }'
 assert 2 'int main() { // return 1;
 return 2; }'
 
+assert 2 'int main() { int x=2; { int x=3; } return x; }'
+assert 2 'int main() { int x=2; { int x=3; } { int y=4; return x; }}'
+assert 3 'int main() { int x=2; { x=3; } return x; }'
+
 echo OK