Use weak_ptr to not keep reference to FileStream

LogStreamReferenceMap was keeping a reference to FileStream
which kept the file open even though Logger was unregistred.

src/easylogging++.cc

@@ -1717,17 +1717,23 @@ void TypedConfigurations::insertFile(Level level, const std::string& fullFilenam
   auto create = [&](Level level) {
     base::LogStreamsReferenceMap::iterator filestreamIter = m_logStreamsReference->find(resolvedFilename);
     base::type::fstream_t* fs = nullptr;
-    if (filestreamIter == m_logStreamsReference->end()) {
+    bool needNewStream = filestreamIter == m_logStreamsReference->end();
+    if (!needNewStream && filestreamIter->second.lock() == nullptr) {
+      // Filestream is expired and exists in map
+      needNewStream = true;
+      m_logStreamsReference->erase(filestreamIter);
+    }
+    if (needNewStream) {
       // We need a completely new stream, nothing to share with
       fs = base::utils::File::newFileStream(resolvedFilename);
       m_filenameMap.insert(std::make_pair(level, resolvedFilename));
       m_fileStreamMap.insert(std::make_pair(level, base::FileStreamPtr(fs)));
-      m_logStreamsReference->insert(std::make_pair(resolvedFilename, base::FileStreamPtr(m_fileStreamMap.at(level))));
+      m_logStreamsReference->insert(std::make_pair(resolvedFilename, base::WeakFileStreamPtr(m_fileStreamMap.at(level))));
     } else {
       // Woops! we have an existing one, share it!
       m_filenameMap.insert(std::make_pair(level, filestreamIter->first));
-      m_fileStreamMap.insert(std::make_pair(level, base::FileStreamPtr(filestreamIter->second)));
-      fs = filestreamIter->second.get();
+      m_fileStreamMap.insert(std::make_pair(level, base::FileStreamPtr(filestreamIter->second.lock())));
+      fs = filestreamIter->second.lock().get();
     }
     if (fs == nullptr) {
       // We display bad file error from newFileStream()
@@ -1851,8 +1857,8 @@ void RegisteredLoggers::unsafeFlushAll(void) {
   ELPP_INTERNAL_INFO(1, "Flushing all log files");
   for (base::LogStreamsReferenceMap::iterator it = m_logStreamsReference.begin();
        it != m_logStreamsReference.end(); ++it) {
-    if (it->second.get() == nullptr) continue;
-    it->second->flush();
+    if (it->second.lock() == nullptr) continue;
+    it->second.lock()->flush();
   }
 }
 

src/easylogging++.h

@@ -1953,7 +1953,8 @@ class Configurations : public base::utils::RegistryWithPred<Configuration, Confi
 
 namespace base {
 typedef std::shared_ptr<base::type::fstream_t> FileStreamPtr;
-typedef std::map<std::string, FileStreamPtr> LogStreamsReferenceMap;
+typedef std::weak_ptr<base::type::fstream_t> WeakFileStreamPtr;
+typedef std::map<std::string, WeakFileStreamPtr> LogStreamsReferenceMap;
 /// @brief Configurations with data types.
 ///
 /// @detail el::Configurations have string based values. This is whats used internally in order to read correct configurations.