Support zero-arity function definition

chibicc.h

@@ -56,6 +56,8 @@ struct Var {
 // Function
 typedef struct Function Function;
 struct Function {
+  Function *next;
+  char *name;
   Node *body;
   Var *locals;
   int stack_size;
@@ -121,6 +123,7 @@ Function *parse(Token *tok);
 typedef enum {
   TY_INT,
   TY_PTR,
+  TY_FUNC,
 } TypeKind;
 
 struct Type {
@@ -131,12 +134,16 @@ struct Type {
 
   // Declaration
   Token *name;
+
+  // Function type
+  Type *return_ty;
 };
 
 extern Type *ty_int;
 
 bool is_integer(Type *ty);
 Type *pointer_to(Type *base);
+Type *func_type(Type *return_ty);
 void add_type(Node *node);
 
 //

codegen.c

@@ -2,6 +2,7 @@
 
 static int depth;
 static char *argreg[] = {"%rdi", "%rsi", "%rdx", "%rcx", "%r8", "%r9"};
+static Function *current_fn;
 
 static void gen_expr(Node *node);
 
@@ -161,7 +162,7 @@ static void gen_stmt(Node *node) {
     return;
   case ND_RETURN:
     gen_expr(node->lhs);
-    printf("  jmp .L.return\n");
+    printf("  jmp .L.return.%s\n", current_fn->name);
     return;
   case ND_EXPR_STMT:
     gen_expr(node->lhs);
@@ -173,30 +174,37 @@ static void gen_stmt(Node *node) {
 
 // Assign offsets to local variables.
 static void assign_lvar_offsets(Function *prog) {
-  int offset = 0;
-  for (Var *var = prog->locals; var; var = var->next) {
-    offset += 8;
-    var->offset = -offset;
+  for (Function *fn = prog; fn; fn = fn->next) {
+    int offset = 0;
+    for (Var *var = fn->locals; var; var = var->next) {
+      offset += 8;
+      var->offset = -offset;
+    }
+    fn->stack_size = align_to(offset, 16);
   }
-  prog->stack_size = align_to(offset, 16);
 }
 
 void codegen(Function *prog) {
   assign_lvar_offsets(prog);
 
-  printf("  .globl main\n");
-  printf("main:\n");
+  for (Function *fn = prog; fn; fn = fn->next) {
+    printf("  .globl %s\n", fn->name);
+    printf("%s:\n", fn->name);
+    current_fn = fn;
 
-  // Prologue
-  printf("  push %%rbp\n");
-  printf("  mov %%rsp, %%rbp\n");
-  printf("  sub $%d, %%rsp\n", prog->stack_size);
+    // Prologue
+    printf("  push %%rbp\n");
+    printf("  mov %%rsp, %%rbp\n");
+    printf("  sub $%d, %%rsp\n", fn->stack_size);
 
-  gen_stmt(prog->body);
-  assert(depth == 0);
+    // Emit code
+    gen_stmt(fn->body);
+    assert(depth == 0);
 
-  printf(".L.return:\n");
-  printf("  mov %%rbp, %%rsp\n");
-  printf("  pop %%rbp\n");
-  printf("  ret\n");
+    // Epilogue
+    printf(".L.return.%s:\n", fn->name);
+    printf("  mov %%rbp, %%rsp\n");
+    printf("  pop %%rbp\n");
+    printf("  ret\n");
+  }
 }

parse.c

@@ -22,6 +22,8 @@
 // accumulated to this list.
 Var *locals;
 
+static Type *typespec(Token **rest, Token *tok);
+static Type *declarator(Token **rest, Token *tok, Type *ty);
 static Node *declaration(Token **rest, Token *tok);
 static Node *compound_stmt(Token **rest, Token *tok);
 static Node *stmt(Token **rest, Token *tok);
@@ -96,16 +98,25 @@ static Type *typespec(Token **rest, Token *tok) {
   return ty_int;
 }
 
-// declarator = "*"* ident
+// type-suffix = ("(" func-params)?
+static Type *type_suffix(Token **rest, Token *tok, Type *ty) {
+  if (equal(tok, "(")) {
+    *rest = skip(tok->next, ")");
+    return func_type(ty);
+  }
+  *rest = tok;
+  return ty;
+}
+
+// declarator = "*"* ident type-suffix
 static Type *declarator(Token **rest, Token *tok, Type *ty) {
   while (consume(&tok, tok, "*"))
     ty = pointer_to(ty);
 
   if (tok->kind != TK_IDENT)
     error_tok(tok, "expected a variable name");
-
+  ty = type_suffix(rest, tok->next, ty);
   ty->name = tok;
-  *rest = tok->next;
   return ty;
 }
 
@@ -470,12 +481,27 @@ static Node *primary(Token **rest, Token *tok) {
   error_tok(tok, "expected an expression");
 }
 
-// program = stmt*
-Function *parse(Token *tok) {
-  tok = skip(tok, "{");
+static Function *function(Token **rest, Token *tok) {
+  Type *ty = typespec(&tok, tok);
+  ty = declarator(&tok, tok, ty);
 
-  Function *prog = calloc(1, sizeof(Function));
-  prog->body = compound_stmt(&tok, tok);
-  prog->locals = locals;
-  return prog;
+  locals = NULL;
+
+  Function *fn = calloc(1, sizeof(Function));
+  fn->name = get_ident(ty->name);
+
+  tok = skip(tok, "{");
+  fn->body = compound_stmt(rest, tok);
+  fn->locals = locals;
+  return fn;
+}
+
+// program = function-definition*
+Function *parse(Token *tok) {
+  Function head = {};
+  Function *cur = &head;
+
+  while (tok->kind != TK_EOF)
+    cur = cur->next = function(&tok, tok);
+  return head.next;
 }

test.sh

@@ -27,87 +27,85 @@ assert() {
   fi
 }
 
-assert 0 '{ return 0; }'
-assert 42 '{ return 42; }'
-assert 21 '{ return 5+20-4; }'
-assert 41 '{ return  12 + 34 - 5 ; }'
-assert 47 '{ return 5+6*7; }'
-assert 15 '{ return 5*(9-6); }'
-assert 4 '{ return (3+5)/2; }'
-assert 10 '{ return -10+20; }'
-assert 10 '{ return - -10; }'
-assert 10 '{ return - - +10; }'
+assert 0 'int main() { return 0; }'
+assert 42 'int main() { return 42; }'
+assert 21 'int main() { return 5+20-4; }'
+assert 41 'int main() { return  12 + 34 - 5 ; }'
+assert 47 'int main() { return 5+6*7; }'
+assert 15 'int main() { return 5*(9-6); }'
+assert 4 'int main() { return (3+5)/2; }'
+assert 10 'int main() { return -10+20; }'
+assert 10 'int main() { return - -10; }'
+assert 10 'int main() { return - - +10; }'
 
-assert 0 '{ return 0==1; }'
-assert 1 '{ return 42==42; }'
-assert 1 '{ return 0!=1; }'
-assert 0 '{ return 42!=42; }'
+assert 0 'int main() { return 0==1; }'
+assert 1 'int main() { return 42==42; }'
+assert 1 'int main() { return 0!=1; }'
+assert 0 'int main() { return 42!=42; }'
 
-assert 1 '{ return 0<1; }'
-assert 0 '{ return 1<1; }'
-assert 0 '{ return 2<1; }'
-assert 1 '{ return 0<=1; }'
-assert 1 '{ return 1<=1; }'
-assert 0 '{ return 2<=1; }'
+assert 1 'int main() { return 0<1; }'
+assert 0 'int main() { return 1<1; }'
+assert 0 'int main() { return 2<1; }'
+assert 1 'int main() { return 0<=1; }'
+assert 1 'int main() { return 1<=1; }'
+assert 0 'int main() { return 2<=1; }'
 
-assert 1 '{ return 1>0; }'
-assert 0 '{ return 1>1; }'
-assert 0 '{ return 1>2; }'
-assert 1 '{ return 1>=0; }'
-assert 1 '{ return 1>=1; }'
-assert 0 '{ return 1>=2; }'
+assert 1 'int main() { return 1>0; }'
+assert 0 'int main() { return 1>1; }'
+assert 0 'int main() { return 1>2; }'
+assert 1 'int main() { return 1>=0; }'
+assert 1 'int main() { return 1>=1; }'
+assert 0 'int main() { return 1>=2; }'
 
-assert 3 '{ int a; a=3; return a; }'
-assert 3 '{ int a=3; return a; }'
-assert 8 '{ int a=3; int z=5; return a+z; }'
+assert 3 'int main() { int a; a=3; return a; }'
+assert 3 'int main() { int a=3; return a; }'
+assert 8 'int main() { int a=3; int z=5; return a+z; }'
 
-assert 3 '{ int a=3; return a; }'
-assert 8 '{ int a=3; int z=5; return a+z; }'
-assert 6 '{ int a; int b; a=b=3; return a+b; }'
-assert 3 '{ int foo=3; return foo; }'
-assert 8 '{ int foo123=3; int bar=5; return foo123+bar; }'
+assert 1 'int main() { return 1; 2; 3; }'
+assert 2 'int main() { 1; return 2; 3; }'
+assert 3 'int main() { 1; 2; return 3; }'
 
-assert 1 '{ return 1; 2; 3; }'
-assert 2 '{ 1; return 2; 3; }'
-assert 3 '{ 1; 2; return 3; }'
+assert 3 'int main() { int a=3; return a; }'
+assert 8 'int main() { int a=3; int z=5; return a+z; }'
+assert 6 'int main() { int a; int b; a=b=3; return a+b; }'
+assert 3 'int main() { int foo=3; return foo; }'
+assert 8 'int main() { int foo123=3; int bar=5; return foo123+bar; }'
 
-assert 3 '{ {1; {2;} return 3;} }'
-assert 5 '{ ;;; return 5; }'
+assert 3 'int main() { if (0) return 2; return 3; }'
+assert 3 'int main() { if (1-1) return 2; return 3; }'
+assert 2 'int main() { if (1) return 2; return 3; }'
+assert 2 'int main() { if (2-1) return 2; return 3; }'
 
-assert 3 '{ if (0) return 2; return 3; }'
-assert 3 '{ if (1-1) return 2; return 3; }'
-assert 2 '{ if (1) return 2; return 3; }'
-assert 2 '{ if (2-1) return 2; return 3; }'
-assert 4 '{ if (0) { 1; 2; return 3; } else { return 4; } }'
-assert 3 '{ if (1) { 1; 2; return 3; } else { return 4; } }'
+assert 55 'int main() { int i=0; int j=0; for (i=0; i<=10; i=i+1) j=i+j; return j; }'
+assert 3 'int main() { for (;;) return 3; return 5; }'
 
-assert 55 '{ int i=0; int j=0; for (i=0; i<=10; i=i+1) j=i+j; return j; }'
-assert 3 '{ for (;;) return 3; return 5; }'
+assert 10 'int main() { int i=0; while(i<10) i=i+1; return i; }'
 
-assert 10 '{ int i=0; while(i<10) i=i+1; return i; }'
+assert 3 'int main() { {1; {2;} return 3;} }'
+assert 5 'int main() { ;;; return 5; }'
 
-assert 3 '{ {1; {2;} return 3;} }'
+assert 10 'int main() { int i=0; while(i<10) i=i+1; return i; }'
+assert 55 'int main() { int i=0; int j=0; while(i<=10) {j=i+j; i=i+1;} return j; }'
 
-assert 10 '{ int i=0; while(i<10) i=i+1; return i; }'
-assert 55 '{ int i=0; int j=0; while(i<=10) {j=i+j; i=i+1;} return j; }'
+assert 3 'int main() { int x=3; return *&x; }'
+assert 3 'int main() { int x=3; int *y=&x; int **z=&y; return **z; }'
+assert 5 'int main() { int x=3; int y=5; return *(&x+1); }'
+assert 3 'int main() { int x=3; int y=5; return *(&y-1); }'
+assert 5 'int main() { int x=3; int *y=&x; *y=5; return x; }'
+assert 7 'int main() { int x=3; int y=5; *(&x+1)=7; return y; }'
+assert 7 'int main() { int x=3; int y=5; *(&y-2+1)=7; return x; }'
+assert 5 'int main() { int x=3; return (&x+2)-&x+3; }'
+assert 8 'int main() { int x, y; x=3; y=5; return x+y; }'
+assert 8 'int main() { int x=3, y=5; return x+y; }'
 
-assert 3 '{ int x=3; return *&x; }'
-assert 3 '{ int x=3; int *y=&x; int **z=&y; return **z; }'
-assert 5 '{ int x=3; int y=5; return *(&x+1); }'
-assert 3 '{ int x=3; int y=5; return *(&y-1); }'
-assert 5 '{ int x=3; int *y=&x; *y=5; return x; }'
-assert 7 '{ int x=3; int y=5; *(&x+1)=7; return y; }'
-assert 7 '{ int x=3; int y=5; *(&y-2+1)=7; return x; }'
-assert 5 '{ int x=3; return (&x+2)-&x+3; }'
-assert 8 '{ int x, y; x=3; y=5; return x+y; }'
-assert 8 '{ int x=3, y=5; return x+y; }'
+assert 3 'int main() { return ret3(); }'
+assert 5 'int main() { return ret5(); }'
+assert 8 'int main() { return add(3, 5); }'
+assert 2 'int main() { return sub(5, 3); }'
+assert 21 'int main() { return add6(1,2,3,4,5,6); }'
+assert 66 'int main() { return add6(1,2,add6(3,4,5,6,7,8),9,10,11); }'
+assert 136 'int main() { return add6(1,2,add6(3,add6(4,5,6,7,8,9),10,11,12,13),14,15,16); }'
 
-assert 3 '{ return ret3(); }'
-assert 5 '{ return ret5(); }'
-assert 8 '{ return add(3, 5); }'
-assert 2 '{ return sub(5, 3); }'
-assert 21 '{ return add6(1,2,3,4,5,6); }'
-assert 66 '{ return add6(1,2,add6(3,4,5,6,7,8),9,10,11); }'
-assert 136 '{ return add6(1,2,add6(3,add6(4,5,6,7,8,9),10,11,12,13),14,15,16); }'
+assert 32 'int main() { return ret32(); } int ret32() { return 32; }'
 
 echo OK

type.c

@@ -13,6 +13,13 @@ Type *pointer_to(Type *base) {
   return ty;
 }
 
+Type *func_type(Type *return_ty) {
+  Type *ty = calloc(1, sizeof(Type));
+  ty->kind = TY_FUNC;
+  ty->return_ty = return_ty;
+  return ty;
+}
+
 void add_type(Node *node) {
   if (!node || node->ty)
     return;