Add enum

chibicc.h

@@ -154,6 +154,7 @@ typedef enum {
   TY_SHORT,
   TY_INT,
   TY_LONG,
+  TY_ENUM,
   TY_PTR,
   TY_FUNC,
   TY_ARRAY,
@@ -212,6 +213,7 @@ Type *copy_type(Type *ty);
 Type *pointer_to(Type *base);
 Type *func_type(Type *return_ty);
 Type *array_of(Type *base, int size);
+Type *enum_type(void);
 void add_type(Node *node);
 
 //

parse.c

@@ -18,17 +18,21 @@
 
 #include "chibicc.h"
 
-// Scope for local, global variables or typedefs.
+// Scope for local variables, global variables, typedefs
+// or enum constants
 typedef struct VarScope VarScope;
 struct VarScope {
   VarScope *next;
   char *name;
   int depth;
+
   Var *var;
   Type *type_def;
+  Type *enum_ty;
+  int enum_val;
 };
 
-// Scope for struct or union tags
+// Scope for struct, union or enum tags
 typedef struct TagScope TagScope;
 struct TagScope {
   TagScope *next;
@@ -41,8 +45,8 @@ typedef struct Scope Scope;
 struct Scope {
   Scope *next;
 
-  // C has two block scopes; one is for variables and the other is
-  // for struct tags.
+  // C has two block scopes; one is for variables/typedefs and
+  // the other is for struct/union/enum tags.
   VarScope *vars;
   TagScope *tags;
 };
@@ -70,6 +74,7 @@ static Var *current_fn;
 
 static bool is_typename(Token *tok);
 static Type *typespec(Token **rest, Token *tok, VarAttr *attr);
+static Type *enum_specifier(Token **rest, Token *tok);
 static Type *declarator(Token **rest, Token *tok, Type *ty);
 static Node *declaration(Token **rest, Token *tok, Type *basety);
 static Node *compound_stmt(Token **rest, Token *tok);
@@ -243,7 +248,7 @@ static void push_tag_scope(Token *tok, Type *ty) {
 }
 
 // typespec = typename typename*
-// typename = "void" | "char" | "short" | "int" | "long"
+// typename = "void" | "_Bool" | "char" | "short" | "int" | "long"
 //            | struct-decl | union-decl | typedef-name
 //
 // The order of typenames in a type-specifier doesn't matter. For
@@ -287,7 +292,7 @@ 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") || ty2) {
+    if (equal(tok, "struct") || equal(tok, "union") || equal(tok, "enum") || ty2) {
       if (counter)
         break;
 
@@ -295,6 +300,8 @@ static Type *typespec(Token **rest, Token *tok, VarAttr *attr) {
         ty = struct_decl(&tok, tok->next);
       } else if (equal(tok, "union")) {
         ty = union_decl(&tok, tok->next);
+      } else if (equal(tok, "enum")) {
+        ty = enum_specifier(&tok, tok->next);
       } else {
         ty = ty2;
         tok = tok->next;
@@ -438,6 +445,59 @@ static Type *typename(Token **rest, Token *tok) {
   return abstract_declarator(rest, tok, ty);
 }
 
+// enum-specifier = ident? "{" enum-list? "}"
+//                | ident ("{" enum-list? "}")?
+//
+// enum-list      = ident ("=" num)? ("," ident ("=" num)?)*
+static Type *enum_specifier(Token **rest, Token *tok) {
+  Type *ty = enum_type();
+
+  // Read a struct tag.
+  Token *tag = NULL;
+  if (tok->kind == TK_IDENT) {
+    tag = tok;
+    tok = tok->next;
+  }
+
+  if (tag && !equal(tok, "{")) {
+    TagScope *sc = find_tag(tag);
+    if (!sc)
+      error_tok(tag, "unknown enum type");
+    if (sc->ty->kind != TY_ENUM)
+      error_tok(tag, "not an enum tag");
+    *rest = tok;
+    return sc->ty;
+  }
+
+  tok = skip(tok, "{");
+
+  // Read an enum-list.
+  int i = 0;
+  int val = 0;
+  while (!equal(tok, "}")) {
+    if (i++ > 0)
+      tok = skip(tok, ",");
+
+    char *name = get_ident(tok);
+    tok = tok->next;
+
+    if (equal(tok, "=")) {
+      val = get_number(tok->next);
+      tok = tok->next->next;
+    }
+
+    VarScope *sc = push_scope(name);
+    sc->enum_ty = ty;
+    sc->enum_val = val++;
+  }
+
+  *rest = tok->next;
+
+  if (tag)
+    push_tag_scope(tag, ty);
+  return ty;
+}
+
 // declaration = typespec (declarator ("=" expr)? ("," declarator ("=" expr)?)*)? ";"
 static Node *declaration(Token **rest, Token *tok, Type *basety) {
   Node head = {};
@@ -473,7 +533,7 @@ static Node *declaration(Token **rest, Token *tok, Type *basety) {
 static bool is_typename(Token *tok) {
   static char *kw[] = {
     "void", "_Bool", "char", "short", "int", "long", "struct", "union",
-    "typedef",
+    "typedef", "enum",
   };
 
   for (int i = 0; i < sizeof(kw) / sizeof(*kw); i++)
@@ -1023,12 +1083,19 @@ static Node *primary(Token **rest, Token *tok) {
     if (equal(tok->next, "("))
       return funcall(rest, tok);
 
-    // Variable
+    // Variable or enum constant
     VarScope *sc = find_var(tok);
-    if (!sc || !sc->var)
+    if (!sc || (!sc->var && !sc->enum_ty))
       error_tok(tok, "undefined variable");
+
+    Node *node;
+    if (sc->var)
+      node = new_var_node(sc->var, tok);
+    else
+      node = new_num(sc->enum_val, tok);
+
     *rest = tok->next;
-    return new_var_node(sc->var, tok);
+    return node;
   }
 
   if (tok->kind == TK_STR) {

test/enum.c

@@ -0,0 +1,18 @@
+#include "test.h"
+
+int main() {
+  ASSERT(0, ({ enum { zero, one, two }; zero; }));
+  ASSERT(1, ({ enum { zero, one, two }; one; }));
+  ASSERT(2, ({ enum { zero, one, two }; two; }));
+  ASSERT(5, ({ enum { five=5, six, seven }; five; }));
+  ASSERT(6, ({ enum { five=5, six, seven }; six; }));
+  ASSERT(0, ({ enum { zero, five=5, three=3, four }; zero; }));
+  ASSERT(5, ({ enum { zero, five=5, three=3, four }; five; }));
+  ASSERT(3, ({ enum { zero, five=5, three=3, four }; three; }));
+  ASSERT(4, ({ enum { zero, five=5, three=3, four }; four; }));
+  ASSERT(4, ({ enum { zero, one, two } x; sizeof(x); }));
+  ASSERT(4, ({ enum t { zero, one, two }; enum t y; sizeof(y); }));
+
+  printf("OK\n");
+  return 0;
+}

tokenize.c

@@ -125,6 +125,7 @@ static bool is_keyword(Token *tok) {
   static char *kw[] = {
     "return", "if", "else", "for", "while", "int", "sizeof", "char",
     "struct", "union", "short", "long", "void", "typedef", "_Bool",
+    "enum",
   };
 
   for (int i = 0; i < sizeof(kw) / sizeof(*kw); i++)

type.c

@@ -19,7 +19,7 @@ static Type *new_type(TypeKind kind, int size, int align) {
 bool is_integer(Type *ty) {
   TypeKind k = ty->kind;
   return k == TY_BOOL || k == TY_CHAR || k == TY_SHORT ||
-         k == TY_INT  || k == TY_LONG;
+         k == TY_INT  || k == TY_LONG || k == TY_ENUM;
 }
 
 Type *copy_type(Type *ty) {
@@ -48,6 +48,10 @@ Type *array_of(Type *base, int len) {
   return ty;
 }
 
+Type *enum_type(void) {
+  return new_type(TY_ENUM, 4, 4);
+}
+
 static Type *get_common_type(Type *ty1, Type *ty2) {
   if (ty1->base)
     return pointer_to(ty1->base);