Merge #13149: Handle unsuccessful fseek(...):s

20ce5af Print a log message if we fail to shrink the debug log file (practicalswift)
29c9bdc Handle unsuccessful fseek(...):s (practicalswift)

Pull request description:

  Handle unsuccessful `fseek(...)`:s.

  **Note to reviewers:** What is the most appropriate course of actions for each of these unsuccessful `fseek(...)`:s?

Tree-SHA512: 5b3d82dbdd15d434d3f08dcb4df62888da4df8541d2586f56a4e529083005f6782c39e10645acd1ec403da83061bbfd8dbf2dddc66e09268d410ad0918c61876

src/logging.cpp

@@ -253,7 +253,11 @@ void BCLog::Logger::ShrinkDebugFile()
     {
         // Restart the file with some of the end
         std::vector<char> vch(RECENT_DEBUG_HISTORY_SIZE, 0);
-        fseek(file, -((long)vch.size()), SEEK_END);
+        if (fseek(file, -((long)vch.size()), SEEK_END)) {
+            LogPrintf("Failed to shrink debug log file: fseek(...) failed\n");
+            fclose(file);
+            return;
+        }
         int nBytes = fread(vch.data(), 1, vch.size(), file);
         fclose(file);