Add GNU expression statement

chibi.h

@@ -98,6 +98,7 @@ typedef enum {
   ND_BLOCK,     // { ... }
   ND_FUNCALL,   // Function call
   ND_EXPR_STMT, // Expression statement
+  ND_STMT_EXPR, // Statement expression
   ND_VAR,       // Variable
   ND_NUM,       // Integer
   ND_NULL,      // Empty statement
@@ -121,7 +122,7 @@ struct Node {
   Node *init;
   Node *inc;
 
-  // Block
+  // Block or statement expression
   Node *body;
 
   // Function call

codegen.c

@@ -139,6 +139,7 @@ static void gen(Node *node) {
     return;
   }
   case ND_BLOCK:
+  case ND_STMT_EXPR:
     for (Node *n = node->body; n; n = n->next)
       gen(n);
     return;

parse.c

@@ -463,6 +463,26 @@ static Node *postfix(void) {
   return node;
 }
 
+// stmt-expr = "(" "{" stmt stmt* "}" ")"
+//
+// Statement expression is a GNU C extension.
+static Node *stmt_expr(Token *tok) {
+  Node *node = new_node(ND_STMT_EXPR, tok);
+  node->body = stmt();
+  Node *cur = node->body;
+
+  while (!consume("}")) {
+    cur->next = stmt();
+    cur = cur->next;
+  }
+  expect(")");
+
+  if (cur->kind != ND_EXPR_STMT)
+    error_tok(cur->tok, "stmt expr returning void is not supported");
+  memcpy(cur, cur->lhs, sizeof(Node));
+  return node;
+}
+
 // func-args = "(" (assign ("," assign)*)? ")"
 static Node *func_args(void) {
   if (consume(")"))
@@ -478,12 +498,19 @@ static Node *func_args(void) {
   return head;
 }
 
-// primary = "(" expr ")" | "sizeof" unary | ident func-args? | str | num
-// args = "(" ident ("," ident)* ")"
+// primary = "(" "{" stmt-expr-tail
+//         | "(" expr ")"
+//         | "sizeof" unary
+//         | ident func-args?
+//         | str
+//         | num
 static Node *primary(void) {
   Token *tok;
 
-  if (consume("(")) {
+  if (tok = consume("(")) {
+    if (consume("{"))
+      return stmt_expr(tok);
+
     Node *node = expr();
     expect(")");
     return node;

test.sh

@@ -183,4 +183,9 @@ assert 106 'int main() { return "\j"[0]; }'
 assert 107 'int main() { return "\k"[0]; }'
 assert 108 'int main() { return "\l"[0]; }'
 
+assert 0 'int main() { return ({ 0; }); }'
+assert 2 'int main() { return ({ 0; 1; 2; }); }'
+assert 1 'int main() { ({ 0; return 1; 2; }); return 3; }'
+assert 3 'int main() { return ({ int x=3; x; }); }'
+
 echo OK

type.c

@@ -74,5 +74,12 @@ void add_type(Node *node) {
       error_tok(node->tok, "invalid pointer dereference");
     node->ty = node->lhs->ty->base;
     return;
+  case ND_STMT_EXPR: {
+    Node *last = node->body;
+    while (last->next)
+      last = last->next;
+    node->ty = last->ty;
+    return;
+  }
   }
 }