Add typeof

parse.c

@@ -123,6 +123,7 @@ static bool is_typename(Token *tok);
 static Type *typespec(Token **rest, Token *tok, VarAttr *attr);
 static Type *typename(Token **rest, Token *tok);
 static Type *enum_specifier(Token **rest, Token *tok);
+static Type *typeof_specifier(Token **rest, Token *tok);
 static Type *type_suffix(Token **rest, Token *tok, Type *ty);
 static Type *declarator(Token **rest, Token *tok, Type *ty);
 static Node *declaration(Token **rest, Token *tok, Type *basety, VarAttr *attr);
@@ -446,7 +447,8 @@ static Type *typespec(Token **rest, Token *tok, VarAttr *attr) {
 
     // Handle user-defined types.
     Type *ty2 = find_typedef(tok);
-    if (equal(tok, "struct") || equal(tok, "union") || equal(tok, "enum") || ty2) {
+    if (equal(tok, "struct") || equal(tok, "union") || equal(tok, "enum") ||
+        equal(tok, "typeof") || ty2) {
       if (counter)
         break;
 
@@ -456,6 +458,8 @@ static Type *typespec(Token **rest, Token *tok, VarAttr *attr) {
         ty = union_decl(&tok, tok->next);
       } else if (equal(tok, "enum")) {
         ty = enum_specifier(&tok, tok->next);
+      } else if (equal(tok, "typeof")) {
+        ty = typeof_specifier(&tok, tok->next);
       } else {
         ty = ty2;
         tok = tok->next;
@@ -764,6 +768,22 @@ static Type *enum_specifier(Token **rest, Token *tok) {
   return ty;
 }
 
+// typeof-specifier = "(" (expr | typename) ")"
+static Type *typeof_specifier(Token **rest, Token *tok) {
+  tok = skip(tok, "(");
+
+  Type *ty;
+  if (is_typename(tok)) {
+    ty = typename(&tok, tok);
+  } else {
+    Node *node = expr(&tok, tok);
+    add_type(node);
+    ty = node->ty;
+  }
+  *rest = skip(tok, ")");
+  return ty;
+}
+
 // declaration = typespec (declarator ("=" expr)? ("," declarator ("=" expr)?)*)? ";"
 static Node *declaration(Token **rest, Token *tok, Type *basety, VarAttr *attr) {
   Node head = {};
@@ -1376,7 +1396,7 @@ static bool is_typename(Token *tok) {
     "void", "_Bool", "char", "short", "int", "long", "struct", "union",
     "typedef", "enum", "static", "extern", "_Alignas", "signed", "unsigned",
     "const", "volatile", "auto", "register", "restrict", "__restrict",
-    "__restrict__", "_Noreturn", "float", "double",
+    "__restrict__", "_Noreturn", "float", "double", "typeof",
   };
 
   for (int i = 0; i < sizeof(kw) / sizeof(*kw); i++)

test/typeof.c

@@ -0,0 +1,13 @@
+#include "test.h"
+
+int main() {
+  ASSERT(3, ({ typeof(int) x=3; x; }));
+  ASSERT(3, ({ typeof(1) x=3; x; }));
+  ASSERT(4, ({ int x; typeof(x) y; sizeof(y); }));
+  ASSERT(8, ({ int x; typeof(&x) y; sizeof(y); }));
+  ASSERT(4, ({ typeof("foo") x; sizeof(x); }));
+  ASSERT(12, sizeof(typeof(struct { int a,b,c; })));
+
+  printf("OK\n");
+  return 0;
+}

tokenize.c

@@ -150,6 +150,7 @@ static bool is_keyword(Token *tok) {
     "default", "extern", "_Alignof", "_Alignas", "do", "signed",
     "unsigned", "const", "volatile", "auto", "register", "restrict",
     "__restrict", "__restrict__", "_Noreturn", "float", "double",
+    "typeof",
   };
 
   for (int i = 0; i < sizeof(kw) / sizeof(*kw); i++)