> compile NEMU

221220000 张三
Linux zzy 5.15.146.1-microsoft-standard-WSL2 #1 SMP Thu Jan 11 04:09:03 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux
 09:09:36 up 13:08,  2 users,  load average: 0.25, 0.20, 0.18

nemu/src/monitor/sdb/expr.c

@@ -165,25 +165,26 @@ int check_parentheses(const Token* arr, size_t p, size_t q) {
   return !is_surrounded;
 }
 
-word_t eval(const Token* arr, size_t p, size_t q) {
+word_t eval(const Token* arr, size_t p, size_t q, bool* success) {
   Assert (p >= 0 && p < q && q < nr_token, "invalid range on eval, "\
     "p = %"PRIuMAX", q = %"PRIuMAX"\n", p, q);
-  if (p > q || p > nr_token || q > nr_token) {
-    /* Bad expression */
-    panic("bad expression");
+  int parten = check_parentheses(arr, p, q);
+  if (parten == -1) {
+    *success = false;
+    return 0;
   }
-  else if (p == q) {
+  if (p == q) {
     /* Single token.
      * For now this token should be a number.
      * Return the value of the number.
      */
     return atoi(arr[p].str);
   }
-  else if (check_parentheses(arr, p, q) == 0) {
+  else if (parten == 0) {
     /* The expression is surrounded by a matched pair of parentheses.
      * If that is the case, just throw away the parentheses.
      */
-    return eval(arr, p + 1, q - 1);
+    return eval(arr, p + 1, q - 1, success);
   }
   else {
     /* We should do more things here. */
@@ -208,8 +209,11 @@ word_t eval(const Token* arr, size_t p, size_t q) {
         op = i;
       }
     }
-    word_t val1 = eval(arr, p, op - 1);
-    word_t val2 = eval(arr, op + 1, q);
+    word_t val1 = eval(arr, p, op - 1, success);
+    word_t val2 = eval(arr, op + 1, q, success);
+    if (success == false) {
+      return 0;
+    }
 
     switch (arr[op].type) {
       case '+': return val1 + val2;
@@ -218,7 +222,6 @@ word_t eval(const Token* arr, size_t p, size_t q) {
       case '/': return val1 / val2;
       default: assert(0);
     }
-    return 0;
   }
 }
 
@@ -231,5 +234,5 @@ word_t expr(char *e, bool *success) {
   /* TODO: Insert codes to evaluate the expression. */
   // TODO();
   *success = true;
-  return eval(tokens, 0, nr_token - 1);
+  return eval(tokens, 0, nr_token - 1, success);
 }