Main: ignore the "pid_file" setting if started as systemd service

Commit 552c30ea caused problems for those people who still had a "pid_file" setting (even though that is obsolete with systemd), because now /run/mpd is owned by root:root (our mpd.service has no User=mpd directive, so systemd starts MPD as root). To work around this problem, and to be able to keep RuntimeDirectory=mpd (which solved a problem of other MPD users), the best compromise seems to just ignore the "pid_file" setting when it is of no use.

Main: ignore the "pid_file" setting if started as systemd service
a4e42172 · Max Kellermann · 8754d705 · a4e42172 · a4e42172
Commit a4e42172 authored Nov 05, 2021 by Max Kellermann
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NEWS NEWS +1 -0

Main.cxx src/Main.cxx +11 -1

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--- a/NEWS
+++ b/NEWS
@@ -2,6 +2,7 @@ ver 0.23.4 (not yet released)
 * output
  - alsa: add option "thesycon_dsd_workaround" to work around device bug
 * fix crash or debug builds if startup fails
+* ignore the "pid_file" setting if started as systemd service
 * Windows
  - enable the "openmpt" decoder plugin

--- a/src/Main.cxx
+++ b/src/Main.cxx
@@ -145,9 +145,19 @@ static void
 glue_daemonize_init(const CommandLineOptions &options,
 		    const ConfigData &config)
 {
+	auto pid_file = config.GetPath(ConfigOption::PID_FILE);
+#ifdef __linux__
+	if (options.systemd && pid_file != nullptr) {
+		pid_file = nullptr;
+		fprintf(stderr,
+			"Ignoring the 'pid_file' setting in systemd mode\n");
+	}
+#endif
 	daemonize_init(config.GetString(ConfigOption::USER),
 		       config.GetString(ConfigOption::GROUP),
-		       config.GetPath(ConfigOption::PID_FILE));
+		       std::move(pid_file));
 	if (options.kill)
 		daemonize_kill();