From 6e37818bbbc9d83ede8692442e38269caabb7ae2 Mon Sep 17 00:00:00 2001
From: wenxiannnn <4bar1p@gmail.com>
Date: Thu, 19 Mar 2026 21:14:29 +0800
Subject: [PATCH] Add if(!file.is_open()) check in write_restart

---
 source/source_md/md_base.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/source/source_md/md_base.cpp b/source/source_md/md_base.cpp
index 390e1c2b08..258e4494e6 100644
--- a/source/source_md/md_base.cpp
+++ b/source/source_md/md_base.cpp
@@ -235,6 +235,13 @@ void MD_base::write_restart(const std::string& global_out_dir)
         std::stringstream ssc;
         ssc << global_out_dir << "Restart_md.txt";
         std::ofstream file(ssc.str().c_str());
+        
+        if (!file.is_open()) 
+        {
+            std::cerr << "Fatal Error in MD_base::write_restart: " << std::endl;
+            std::cerr << "Cannot open file " << ssc.str() << " for writing." << std::endl;
+            std::cerr << "Please check if the directory exists and has write permissions." << std::endl;
+        }
 
         file << step_ + step_rst_ << std::endl;
         file << md_tfirst << std::endl;