implicit return 0 for main

boot.c

@@ -430,20 +430,18 @@ int parse_type() {
         next_token();
         ignore_const();
         if (token_type == TOKEN_STAR) {
+            next_token();
             ignore_const();
-            return type | TYPE_PTR_MASK;
+            type = type | TYPE_PTR_MASK;
         }
         unget_token();
         return type;
-    } else {
-        return -1;
     }
+    return -1;
 }
 
 // asm
 
-int epilog_label;
-
 int local_table[4096]; // id -> local id
 int next_local_id = 1;
 int max_local_id = 1;
@@ -760,7 +758,7 @@ void _asm_ri(const char* op, int rd, int rs1, int imm) {
     }
 }
 
-void _asm_branch(const char* op, int rs1, int label) {
+void asm_branch(const char* op, int rs1, int label) {
     const char* rs1_name = trivialize(rs1, REG_T0);
     printf("  %s %s, L%d\n", op, rs1_name, label);
 }
@@ -869,11 +867,11 @@ int asm_rr_cmp(const char* op, int rs1, int rs2) {
 }
 
 void asm_beqz(int rs1, int label) {
-    _asm_branch("beqz", rs1, label);
+    asm_branch("beqz", rs1, label);
 }
 
 void asm_bnez(int rs1, int label) {
-    _asm_branch("bnez", rs1, label);
+    asm_branch("bnez", rs1, label);
 }
 
 void asm_j(int label) {
@@ -895,12 +893,20 @@ int cont_label_stack[4096];
 int break_label_stack_size;
 int cont_label_stack_size;
 
-int asm_get_break_label() {
-    return break_label_stack[break_label_stack_size - 1];
+void asm_break() {
+    if (break_label_stack_size == 0) {
+        eprintf("break without loop\n");
+        exit(1);
+    }
+    asm_j(break_label_stack[break_label_stack_size - 1]);
 }
 
-int asm_get_cont_label() {
-    return cont_label_stack[cont_label_stack_size - 1];
+void asm_continue() {
+    if (cont_label_stack_size == 0) {
+        eprintf("continue without loop\n");
+        exit(1);
+    }
+    asm_j(cont_label_stack[cont_label_stack_size - 1]);
 }
 
 void asm_push_label(int break_label, int cont_label) {
@@ -913,6 +919,12 @@ void asm_pop_label() {
     --cont_label_stack_size;
 }
 
+int epilog_label;
+
+void asm_return() {
+    asm_j(epilog_label);
+}
+
 int log_step_of(int type) {
     return 2 * (type == TYPE_INT_PTR);
 }
@@ -1048,7 +1060,7 @@ int parse_function_call(int id) {
         asm_mv(rd, REG_A0);
         return rd;
     }
-    return -1;
+    return REG_ZERO;
 }
 
 int parse_primary_expr() {
@@ -1515,19 +1527,17 @@ void parse_stmt() {
     } else if (token_type == TOKEN_RETURN) {
         next_token();
         if (token_type == TOKEN_SEMICOLON) {
-            asm_j(epilog_label);
+            asm_return();
             return;
         }
         unget_token();
         int rs1 = parse_expr();
         asm_mv(REG_A0, rs1);
-        asm_j(epilog_label);
+        asm_return();
     } else if (token_type == TOKEN_BREAK) {
-        int label = asm_get_break_label();
-        asm_j(label);
+        asm_break();
     } else if (token_type == TOKEN_CONTINUE) {
-        int label = asm_get_cont_label();
-        asm_j(label);
+        asm_continue();
     } else if (token_type == TOKEN_SEMICOLON) {
         unget_token();
     } else if ((decl_type = parse_type()) >= 0) {
@@ -1614,7 +1624,10 @@ void parse_function(const char* name) {
         unget_token();
         parse_stmt();
     }
-    asm_j(epilog_label);
+    if (streq(name, "main")) {
+        asm_mv(REG_A0, REG_ZERO);
+    }
+    asm_return();
     int reg_used = max_reg_id - REG_S2;
     if (reg_used > 14) reg_used = 14;
     int frame_size = (max_local_id - 1 + reg_used + 2) * 8;
@@ -1752,5 +1765,4 @@ void dump_string_table() {
 int main() {
     parse_top_level();
     dump_string_table();
-    return 0;
 }