Merge #19809: log: Prefix log messages with function name and source code location if -logsourcelocations is set

b4511e2e2e log: Prefix log messages with function name if -logsourcelocations is set (practicalswift)

Pull request description:

  Prefix log messages with function name if `-logfunctionnames` is set.

  Yes, exactly like `-logthreadnames` but for function names instead of thread names :)

  This is a small developer ergonomics improvement: I've found this to be a cheap/simple way to correlate log output and originating function.

  For me it beats the ordinary cycle of 1.) try to figure out a regexp matching the static part of the dynamic log message, 2.) `git grep -E 'Using .* MiB out of .* requested for signature cache'`, 3.) `mcedit filename.cpp` (`openemacs filename.cpp` works too!) and 4.) search for log message and scroll up to find the function name :)

  Without any logging parameters:

  ```
  $ src/bitcoind -regtest
  2020-08-25T03:29:04Z Using RdRand as an additional entropy source
  2020-08-25T03:29:04Z Using 16 MiB out of 32/2 requested for signature cache, able to store 524288 elements
  2020-08-25T03:29:04Z Using 16 MiB out of 32/2 requested for script execution cache, able to store 524288 elements
  2020-08-25T03:29:04Z Loaded best chain: hashBestChain=0fff88f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e22ff height=0 date=2011-02-02T23:16:42Z progress=1.000000
  2020-08-25T03:29:04Z block tree size = 1
  2020-08-25T03:29:04Z nBestHeight = 0
  2020-08-25T03:29:04Z Imported mempool transactions from disk: 0 succeeded, 0 failed, 0 expired, 0 already there, 0 waiting for initial broadcast
  2020-08-25T03:29:04Z 0 addresses found from DNS seeds
  ```

  With `-logthreadnames` and `-logfunctionnames`:

  ```
  $ src/bitcoind -regtest -logthreadnames -logfunctionnames
  2020-08-25T03:29:04Z [init] [ReportHardwareRand] Using RdRand as an additional entropy source
  2020-08-25T03:29:04Z [init] [InitSignatureCache] Using 16 MiB out of 32/2 requested for signature cache, able to store 524288 elements
  2020-08-25T03:29:04Z [init] [InitScriptExecutionCache] Using 16 MiB out of 32/2 requested for script execution cache, able to store 524288 elements
  2020-08-25T03:29:04Z [init] [LoadChainTip] Loaded best chain: hashBestChain=0fff88f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e22ff height=0 date=2011-02-02T23:16:42Z progress=1.000000
  2020-08-25T03:29:04Z [init] [AppInitMain] block tree size = 1
  2020-08-25T03:29:04Z [init] [AppInitMain] nBestHeight = 0
  2020-08-25T03:29:04Z [loadblk] [LoadMempool] Imported mempool transactions from disk: 0 succeeded, 0 failed, 0 expired, 0 already there, 0 waiting for initial broadcast
  2020-08-25T03:29:04Z [dnsseed] [ThreadDNSAddressSeed] 0 addresses found from DNS seeds
  ```

ACKs for top commit:
  laanwj:
    Code review ACK b4511e2e2e
  MarcoFalke:
    review ACK b4511e2e2e 🌃

Tree-SHA512: d100f5364630c323f31d275259864c597f7725e462d5f4bdedcc7033ea616d7fc0d16ef1b2af557e692f4deea73c6773ccfc681589e7bf6ba970b9ec169040c7

src/logging.cpp

@@ -5,6 +5,7 @@
 
 #include <logging.h>
 #include <util/threadnames.h>
+#include <util/string.h>
 #include <util/time.h>
 
 #include <mutex>
@@ -236,11 +237,15 @@ namespace BCLog {
     }
 }
 
-void BCLog::Logger::LogPrintStr(const std::string& str)
+void BCLog::Logger::LogPrintStr(const std::string& str, const std::string& logging_function, const std::string& source_file, const int source_line)
 {
     StdLockGuard scoped_lock(m_cs);
     std::string str_prefixed = LogEscapeMessage(str);
 
+    if (m_log_sourcelocations && m_started_new_line) {
+        str_prefixed.insert(0, "[" + RemovePrefix(source_file, "./") + ":" + ToString(source_line) + "] [" + logging_function + "] ");
+    }
+
     if (m_log_threadnames && m_started_new_line) {
         str_prefixed.insert(0, "[" + util::ThreadGetInternalName() + "] ");
     }