Improve handling of the debug log file.

Fix handling of empty strings in uci options and reassigning of the log file

Fixes https://github.com/official-stockfish/Stockfish/issues/3650

Closes https://github.com/official-stockfish/Stockfish/pull/3655

No functional change

AUTHORS

@@ -1,4 +1,4 @@
-# List of authors for Stockfish, as of June 14, 2021
+# List of authors for Stockfish
 
 # Founders of the Stockfish project and fishtest infrastructure
 Tord Romstad (romstad)

src/misc.cpp

@@ -110,7 +110,14 @@ public:
 
     static Logger l;
 
-    if (!fname.empty() && !l.file.is_open())
+    if (l.file.is_open())
+    {
+        cout.rdbuf(l.out.buf);
+        cin.rdbuf(l.in.buf);
+        l.file.close();
+    }
+
+    if (!fname.empty())
     {
         l.file.open(fname, ifstream::out);
 
@@ -123,12 +130,6 @@ public:
         cin.rdbuf(&l.in);
         cout.rdbuf(&l.out);
     }
-    else if (fname.empty() && l.file.is_open())
-    {
-        cout.rdbuf(l.out.buf);
-        cin.rdbuf(l.in.buf);
-        l.file.close();
-    }
   }
 };
 

src/ucioption.cpp

@@ -164,7 +164,7 @@ Option& Option::operator=(const string& v) {
 
   assert(!type.empty());
 
-  if (   (type != "button" && v.empty())
+  if (   (type != "button" && type != "string" && v.empty())
       || (type == "check" && v != "true" && v != "false")
       || (type == "spin" && (stof(v) < min || stof(v) > max)))
       return *this;