Fixed rotating_logger_mt does not rotate properly if app restarts #116

include/spdlog/details/file_helper.h

@@ -113,6 +113,29 @@ public:
 
     }
 
+    long size()
+    {
+        if (!_fd)
+            throw spdlog_ex("Cannot use size() on closed file " + _filename);
+
+        auto pos = ftell(_fd);
+        if (fseek(_fd, 0, SEEK_END) != 0)
+            throw spdlog_ex("fseek failed on file " + _filename);
+
+        auto size = ftell(_fd);
+
+        if(fseek(_fd, pos, SEEK_SET) !=0)
+            throw spdlog_ex("fseek failed on file " + _filename);
+
+        if (size == -1)
+            throw spdlog_ex("ftell failed on file " + _filename);
+
+
+        return size;
+
+
+    }
+
     const std::string& filename() const
     {
         return _filename;
@@ -132,6 +155,8 @@ public:
         }
     }
 
+
+
 private:
     FILE* _fd;
     std::string _filename;

include/spdlog/sinks/file_sinks.h

@@ -82,6 +82,7 @@ public:
         _file_helper(force_flush)
     {
         _file_helper.open(calc_filename(_base_filename, 0, _extension));
+        _current_size = _file_helper.size(); //expensive. called only once
     }
 
     void flush() override