Merge #13159: Don't close old debug log file handle prematurely when …

…trying to re-open (on SIGHUP)

Summary:
75ea00f391b742e435c650aae3e827aad913d552 Remove unused fsbridge::freopen (practicalswift)
cceedbc4bf1056db17e0adf76d0db45b94777671 Don't close old debug log file handle prematurely when trying to re-open (on SIGHUP) (practicalswift)

Pull request description:

  Don't close old debug log file handle prematurely when trying to re-open (on `SIGHUP`).

  Context: bitcoin/bitcoin#13148 (comment)

  Thanks @ajtowns!

Tree-SHA512: c436b4286f00fc428b60269b6d6321f435c72c7ccec3c15b2194aac71196529b30f32c2384b418ffe3ed67ba7ee8ec51f4c9c5748e65945697c0437eafcdacd1

Backport of Core PR13159
bitcoin/bitcoin#13159

Depends on D3976

Test Plan:
  make check
  ./bitcoind -regtest -daemon
  cd <path>/.bitcoin/regtest
  mv debug.log{,.old}
  touch debug.log; chmod 400 debug.log
  killall -HUP bitcoind
  <patch>/bitcoin-abc/build/src/bitcoin-cli -regtest savemempool
Verify that the new debug.log file is empty and debug.log.old continued to be written to

Reviewers: deadalnix, Fabien, jasonbcox, O1 Bitcoin ABC, #bitcoin_abc

Reviewed By: Fabien, O1 Bitcoin ABC, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D3979

src/fs.cpp

@@ -6,8 +6,5 @@ FILE *fopen(const fs::path &p, const char *mode) {
     return ::fopen(p.string().c_str(), mode);
 }
 
-FILE *freopen(const fs::path &p, const char *mode, FILE *stream) {
-    return ::freopen(p.string().c_str(), mode, stream);
-}
 
 } // fsbridge

src/fs.h

@@ -26,7 +26,6 @@ namespace fs = boost::filesystem;
 /** Bridge operations to C stdio */
 namespace fsbridge {
 FILE *fopen(const fs::path &p, const char *mode);
-FILE *freopen(const fs::path &p, const char *mode, FILE *stream);
-};
+}; // namespace fsbridge
 
 // clang-format on

src/logging.cpp

@@ -178,14 +178,14 @@ void BCLog::Logger::LogPrintStr(const std::string &str) {
             if (m_reopen_file) {
                 m_reopen_file = false;
                 fs::path pathDebug = GetDebugLogPath();
-                m_fileout = fsbridge::freopen(pathDebug, "a", m_fileout);
-                if (!m_fileout) {
-                    return;
+                FILE *new_fileout = fsbridge::fopen(pathDebug, "a");
+                if (new_fileout) {
+                    // unbuffered.
+                    setbuf(m_fileout, nullptr);
+                    fclose(m_fileout);
+                    m_fileout = new_fileout;
                 }
-                // unbuffered.
-                setbuf(m_fileout, nullptr);
             }
-
             FileWriteStr(strTimestamped, m_fileout);
         }
     }