[ML] Only log failure to ignore SIGPIPE once

include/core/CNamedPipeFactory.h

@@ -90,6 +90,11 @@ class CORE_EXPORT CNamedPipeFactory : private CNonInstantiatable {
     //! Default path for named pipes.
     static std::string defaultPath();
 
+    //! Log warnings that have been stored because they were detected very
+    //! early in the program lifecycle.  Programs using named pipes should
+    //! call this method once, after setting up logging.
+    static void logDeferredWarnings();
+
 private:
 #ifdef Windows
     using TPipeHandle = HANDLE;

lib/core/CLogger.cc

@@ -314,6 +314,8 @@ bool CLogger::reconfigureLogToNamedPipe(const std::string& pipeName) {
 
     LOG_DEBUG(<< "Logger is logging to named pipe " << pipeName);
 
+    CNamedPipeFactory::logDeferredWarnings();
+
     return true;
 }
 

lib/core/CNamedPipeFactory.cc

@@ -173,13 +173,15 @@ std::string CNamedPipeFactory::defaultPath() {
     return path;
 }
 
-CNamedPipeFactory::TPipeHandle
-CNamedPipeFactory::initPipeHandle(const std::string& fileName, bool forWrite) {
-    if (!SIGPIPE_IGNORED) {
+void CNamedPipeFactory::logDeferredWarnings() {
+    if (SIGPIPE_IGNORED == false) {
         LOG_WARN(<< "Failed to ignore SIGPIPE - this process will not terminate "
                     "gracefully if a process it is writing to via a named pipe dies");
     }
+}
 
+CNamedPipeFactory::TPipeHandle
+CNamedPipeFactory::initPipeHandle(const std::string& fileName, bool forWrite) {
     bool madeFifo(false);
 
     // If the name already exists, ensure it refers directly (i.e. not via a

lib/core/CNamedPipeFactory_Windows.cc

@@ -83,6 +83,10 @@ std::string CNamedPipeFactory::defaultPath() {
     return PIPE_PREFIX;
 }
 
+void CNamedPipeFactory::logDeferredWarnings() {
+    // No-op
+}
+
 CNamedPipeFactory::TPipeHandle
 CNamedPipeFactory::initPipeHandle(const std::string& fileName, bool forWrite) {
     // Size of named pipe buffer