添加认证清理函数，优化内存管理；修复问题查询和处理中的内存释放，增强代码稳定性

include/server/auth.h

@@ -12,7 +12,8 @@ int user_permission_handler(mg_connection* conn, void* cbdata);
 int admin_handler(mg_connection* conn, void* cbdata);
 
 extern char* secret;
-
 extern char* admin_session;
 
+void auth_cleanup();
+
 #endif // SERVER_AUTH_H

src/db/problems.cpp

@@ -176,7 +176,7 @@ extern "C"
     {
         auto problems = std::vector<int>{};
 
-        leveldb::Iterator* it = problems_db->NewIterator(leveldb::ReadOptions());
+        auto it = problems_db->NewIterator(leveldb::ReadOptions());
         for (it->SeekToFirst(); it->Valid(); it->Next()) {
             if (!it->key().compare("@")) continue;
             problems.emplace_back(std::stoi(it->key().ToString()));
@@ -184,8 +184,10 @@ extern "C"
 
         if (!it->status().ok()) {
             std::println(stderr, "Failed to get all problems: {}", it->status().ToString());
+            delete it;
             return 0;
         }
+        delete it;
         auto json = nlohmann::json(problems);
 
         *result = strdup(json.dump().c_str());

src/server/auth/auth.c

@@ -1,7 +1,14 @@
 #include "server/auth.h"
 
 #include <stddef.h>
+#include <stdlib.h>
 
 char* secret = NULL;
 
 char* admin_session = NULL;
+
+void auth_cleanup()
+{
+    if (secret) free(secret);
+    if (admin_session) free(admin_session);
+}

src/server/study/problems.c

@@ -141,9 +141,12 @@ static void impl_query(mg_connection* conn, problem_form_t* form, int permission
     }
     if (pr2) {
         res_query_problem2(conn, result1, result2, result3);
+        free(result2);
     } else {
         res_query_problem(conn, result1, result3);
     }
+    free(result1);
+    free(result3);
 }
 
 static void impl_modify(mg_connection* conn, problem_form_t* form)
@@ -210,6 +213,7 @@ static void impl_all(mg_connection* conn, problem_form_t* form)
         return;
     }
     res_all_problems(conn, result);
+    free(result);
 }
 
 int problems_handler(mg_connection* conn, void* cbdata)