Merge bitcoin/bitcoin#25256: logging: fix logging empty thread name

3a171f742c31addf5a343e8a6905054a1fbb12aa logging: fix logging empty threadname (klementtan)

Pull request description:

  Currently, `leveldb` background thread does not have a thread name and as a result, an empty thread name is logged.

  This PR fixes this by logging thread name as `"unknown"` if the thread name is empty

  On master:
  ```txt
  2022-06-02T14:30:38Z [] [leveldb:debug] Generated table #281@0: 1862 keys, 138303 bytes
  ```

  On this PR:
  ```txt
  2022-06-02T14:30:38Z [unknown] [leveldb:debug] Generated table #281@0: 1862 keys, 138303 bytes
  ```

ACKs for top commit:
  laanwj:
    Code review ACK 3a171f742c31addf5a343e8a6905054a1fbb12aa
  hebasto:
    ACK 3a171f742c31addf5a343e8a6905054a1fbb12aa

Tree-SHA512: 0af0fa5c4ddd3640c6dab9595fe9d97f74d0e0f4b41287a6630cf8ac5a21240250e0659ec4ac5a561e888d522f5304bf627104de2aba0fd0a86c1222de0897c2

1 files changed, 2 insertions, 1 deletions

diff --git a/src/logging.cpp b/src/logging.cpp
index f1a86f0dce..1e2c1d5a77 100644
--- a/src/logging.cpp
+++ b/src/logging.cpp
@@ -364,7 +364,8 @@ void BCLog::Logger::LogPrintStr(const std::string& str, const std::string& loggi
     }
 
     if (m_log_threadnames && m_started_new_line) {
-        str_prefixed.insert(0, "[" + util::ThreadGetInternalName() + "] ");
+        const auto threadname = util::ThreadGetInternalName();
+        str_prefixed.insert(0, "[" + (threadname.empty() ? "unknown" : threadname) + "] ");
     }
 
     str_prefixed = LogTimestampStr(str_prefixed);