Don't suppress IO errors when writing files

* Close or flush streams explicitely so writing is not
  deferred
    * to catch errors in the right place
    * to avoid suppressing errors completely when writing
      would be deferred to the destructor invocation
* Improve comments

CMakeLists.txt

@@ -10,7 +10,7 @@ set(META_APP_URL "https://github.com/${META_APP_AUTHOR}/${META_PROJECT_NAME}")
 set(META_APP_DESCRIPTION "C++ library for reading and writing MP4 (iTunes), ID3, Vorbis, Opus, FLAC and Matroska tags")
 set(META_VERSION_MAJOR 9)
 set(META_VERSION_MINOR 1)
-set(META_VERSION_PATCH 1)
+set(META_VERSION_PATCH 2)
 set(META_REQUIRED_CPP_UNIT_VERSION 1.14.0)
 set(META_ADD_DEFAULT_CPP_UNIT_TEST_APPLICATION ON)
 

backuphelper.cpp

@@ -68,19 +68,21 @@ void restoreOriginalFileFromBackupFile(
     }
     // remove original file and restore backup
     std::remove(originalPath.c_str());
-    if (std::rename(BasicFileInfo::pathForOpen(backupPath), BasicFileInfo::pathForOpen(originalPath))) {
-        // can't rename/move the file (maybe backup dir on another partition) -> make a copy instead
-        try {
-            // need to open all streams again
-            backupStream.exceptions(ios_base::failbit | ios_base::badbit);
-            originalStream.exceptions(ios_base::failbit | ios_base::badbit);
-            backupStream.open(backupPath, ios_base::in | ios_base::binary);
-            originalStream.open(originalPath, ios_base::out | ios_base::binary);
-            originalStream << backupStream.rdbuf();
-            // TODO: callback for progress updates
-        } catch (const std::ios_base::failure &failure) {
-            throw std::ios_base::failure("Unable to restore original file from backup file \"" % backupPath % "\" after failure: " + failure.what());
-        }
+    if (std::rename(BasicFileInfo::pathForOpen(backupPath), BasicFileInfo::pathForOpen(originalPath)) == 0) {
+        return;
+    }
+    // can't rename/move the file (maybe backup dir on another partition) -> make a copy instead
+    try {
+        // need to open all streams again
+        backupStream.exceptions(ios_base::failbit | ios_base::badbit);
+        originalStream.exceptions(ios_base::failbit | ios_base::badbit);
+        backupStream.open(backupPath, ios_base::in | ios_base::binary);
+        originalStream.open(originalPath, ios_base::out | ios_base::binary);
+        originalStream << backupStream.rdbuf();
+        originalStream.flush();
+        // TODO: callback for progress updates
+    } catch (const std::ios_base::failure &failure) {
+        throw std::ios_base::failure("Unable to restore original file from backup file \"" % backupPath % "\" after failure: " + failure.what());
     }
 }
 
@@ -181,6 +183,7 @@ void createBackupFile(const std::string &backupDir, const std::string &originalP
             originalStream.open(BasicFileInfo::pathForOpen(originalPath), ios_base::in | ios_base::binary);
             // do the actual copying
             backupStream << originalStream.rdbuf();
+            backupStream.flush();
             // streams are closed in the next try-block
             // TODO: callback for progress updates
         } catch (const std::ios_base::failure &failure) {

matroska/matroskacontainer.cpp

@@ -1845,7 +1845,7 @@ void MatroskaContainer::internalMakeFile(Diagnostics &diag, AbortableProgressFee
             }
         }
 
-        // flush output stream
+        // prevent deferring final write operations (to catch and handle possible errors here)
         outputStream.flush();
 
         // handle errors (which might have been occurred after renaming/creating backup file)

mediafileinfo.cpp

@@ -1544,6 +1544,8 @@ void MediaFileInfo::makeMp3File(Diagnostics &diag, AbortableProgressFeedback &pr
                     diag.emplace_back(DiagLevel::Warning, "Unable to write ID3v1 tag.", context);
                 }
             }
+            // prevent deferring final write operations (to catch and handle possible errors here)
+            stream().flush();
         }
         return;
     }
@@ -1747,13 +1749,14 @@ void MediaFileInfo::makeMp3File(Diagnostics &diag, AbortableProgressFeedback &pr
                 reportPathChanged(saveFilePath());
                 m_saveFilePath.clear();
             }
-            // stream is useless for further usage because it is write-only
+            // prevent deferring final write operations (to catch and handle possible errors here); stream is useless for further
+            // usage anyways because it is write-only
             outputStream.close();
         } else {
             const auto newSize = static_cast<std::uint64_t>(outputStream.tellp());
             if (newSize < size()) {
                 // file is smaller after the modification -> truncate
-                // -> close stream before truncating
+                // -> prevent deferring final write operations
                 outputStream.close();
                 // -> truncate file
                 if (truncate(BasicFileInfo::pathForOpen(path()), static_cast<streamoff>(newSize)) == 0) {
@@ -1762,7 +1765,10 @@ void MediaFileInfo::makeMp3File(Diagnostics &diag, AbortableProgressFeedback &pr
                     diag.emplace_back(DiagLevel::Critical, "Unable to truncate the file.", context);
                 }
             } else {
-                // file is longer after the modification -> just report new size
+                // file is longer after the modification
+                // -> prevent deferring final write operations (to catch and handle possible errors here)
+                outputStream.flush();
+                // -> report new size
                 reportSizeChanged(newSize);
             }
         }

mp4/mp4container.cpp

@@ -881,7 +881,7 @@ calculatePadding:
             }
         }
 
-        // flush output stream
+        // prevent deferring final write operations (to catch and handle possible errors here)
         outputStream.flush();
 
         // handle errors (which might have been occurred after renaming/creating backup file)

ogg/oggcontainer.cpp

@@ -580,6 +580,9 @@ void OggContainer::internalMakeFile(Diagnostics &diag, AbortableProgressFeedback
             OggPage::updateChecksum(fileInfo().stream(), offset);
         }
 
+        // prevent deferring final write operations (to catch and handle possible errors here)
+        fileInfo().stream().flush();
+
         // clear iterator
         m_iterator.clear(fileInfo().stream(), startOffset(), fileInfo().size());