From 7fc0624f07b0451f8a8c997e18c29da10076aa38 Mon Sep 17 00:00:00 2001
From: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
Date: Sat, 13 Apr 2013 00:24:36 +0200
Subject: [PATCH] When re-execing, try with --test-config first, and revert if
 it fails.

---
 main.cpp | 51 +++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 49 insertions(+), 2 deletions(-)

diff --git a/main.cpp b/main.cpp
index f220cfb..afc3edf 100644
--- a/main.cpp
+++ b/main.cpp
@@ -10,6 +10,8 @@
 #include <sys/ioctl.h>
 #include <sys/poll.h>
 #include <sys/time.h>
+#include <sys/types.h>
+#include <sys/wait.h>
 #include <signal.h>
 #include <errno.h>
 #include <ctype.h>
@@ -241,6 +243,45 @@ void create_streams(const Config &config,
 		}
 	}
 }
+	
+bool dry_run_config(const std::string &argv0, const std::string &config_filename)
+{
+	char *argv0_copy = strdup(argv0.c_str());
+	char *config_filename_copy = strdup(config_filename.c_str());
+
+	pid_t pid = fork();
+	switch (pid) {
+	case -1:
+		perror("fork()");
+		free(argv0_copy);
+		free(config_filename_copy);
+		return false;
+	case 0:
+		// Child.
+		execlp(argv0_copy, argv0_copy, "--test-config", config_filename_copy, NULL);
+		perror(argv0_copy);
+		_exit(1);
+	default:
+		// Parent.
+		break;
+	}
+		
+	free(argv0_copy);
+	free(config_filename_copy);
+
+	int status;
+	pid_t err;
+	do {
+		err = waitpid(pid, &status, 0);
+	} while (err == -1 && errno == EINTR);
+
+	if (err == -1) {
+		perror("waitpid()");
+		return false;
+	}	
+
+	return (WIFEXITED(status) && WEXITSTATUS(status) == 0);
+}
 
 int main(int argc, char **argv)
 {
@@ -275,8 +316,6 @@ int main(int argc, char **argv)
 		config_filename = argv[optind++];
 	}
 
-	struct timeval serialize_start;
-
 	Config config;
 	if (!parse_config(config_filename, &config)) {
 		exit(1);
@@ -285,10 +324,12 @@ int main(int argc, char **argv)
 		exit(0);
 	}
 
+start:
 	fprintf(stderr, "\nCubemap " SERVER_VERSION " starting.\n");
 	servers = new ServerPool(config.num_servers);
 
 	CubemapStateProto loaded_state;
+	struct timeval serialize_start;
 	set<string> deserialized_stream_ids;
 	map<string, Input *> deserialized_inputs;
 	map<int, Acceptor *> deserialized_acceptors;
@@ -384,6 +425,12 @@ int main(int argc, char **argv)
 	state_fd = make_tempfile(collect_state(
 		serialize_start, acceptors, inputs, servers));
 	delete servers;
+
+	if (!dry_run_config(argv[0], config_filename)) {
+		fprintf(stderr, "ERROR: %s --test-config failed. Restarting old version instead of new.\n", argv[0]);
+		hupped = false;
+		goto start;
+	}
 	 
 	char buf[16];
 	sprintf(buf, "%d", state_fd);
-- 
2.39.2