Log: Allow direct logging to journald if ENABLE_JOURNALD is set

This allows for more metadata in the journal over syslog, like automatic
line and source file information being logged

Makefile

@@ -156,8 +156,17 @@ else
 	LTO := $(THREADS)
 endif
 
-#? Look for syslog.h
-override ADDFLAGS += $(strip $(shell echo "#include <syslog.h>\nint main() {}" | $(CXX) -o /dev/null -x c++ - >/dev/null 2>&1 && echo "-DHAVE_SYSLOG"))
+#? Enable journald direct logging
+ifeq ($(ENABLE_JOURNALD),true)
+	HAVE_JOURNALD := $(shell echo "#include <systemd/sd-journal.h>\nint main() {}" | $(CXX) -lsystemd -o /dev/null -x c++ - >/dev/null 2>&1 && echo true)
+endif
+
+ifeq ($(HAVE_JOURNALD),true)
+	override ADDFLAGS += -DHAVE_JOURNALD -lsystemd
+else
+	#? Look for syslog.h
+	override ADDFLAGS += $(strip $(shell echo '#include <syslog.h>\nint main() {}' | $(CXX) -o /dev/null -x c++ - >/dev/null 2>&1 && echo '-DHAVE_SYSLOG'))
+endif
 
 #? The Directories, Source, Includes, Objects and Binary
 SRCDIR		:= src

src/btop_log.cpp

@@ -7,7 +7,9 @@
 #include <mutex>
 #include <string>
 
-#if defined(HAVE_SYSLOG)
+#if defined(HAVE_JOURNALD)
+	#include <systemd/sd-journal.h>
+#elif defined(HAVE_SYSLOG)
 	#include <syslog.h>
 #endif
 
@@ -54,14 +56,19 @@ namespace Logger {
 		atomic_lock lck(busy, true);
 		lose_priv neutered{};
 
-#if defined(HAVE_SYSLOG)
+#if defined(HAVE_JOURNALD) || defined(HAVE_SYSLOG)
 		int status = LOG_DEBUG;
 		switch (level) {
 			case 1: status = LOG_ERR; break;
 			case 2: status = LOG_WARNING; break;
 			case 3: status = LOG_INFO; break;
 			case 4: status = LOG_DEBUG; break;
 		}
+#endif
+
+#if defined(HAVE_JOURNALD)
+		sd_journal_print(status, msg.data());
+#elif defined(HAVE_SYSLOG)
 		syslog(status, msg.data());
 #else
 		if (logfile.empty()) {