Fix GCC warnings with _FORTIFY_SOURCE=2

- Decleare some return values with (void)fn(), for cases where
  we don't care (dropping table headers), or best effor
- Check return value from fgets() and chdir() in some cases that
  are valid, i.e., continuing execution is pointless

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/cgroup.c

@@ -54,7 +54,7 @@ void cgroup_init(void)
 	}
 
 	/* Skip first line, header */
-	fgets(buf, sizeof(buf), fp);
+	(void)fgets(buf, sizeof(buf), fp);
 	while (fgets(buf, sizeof(buf), fp)) {
 		char *cgroup;
 		char rc[80];

src/helpers.c

@@ -432,14 +432,14 @@ void set_hostname(char **hostname)
 			return;
 		}
 
-		fgets(*hostname, st.st_size, fp);
+		if (fgets(*hostname, st.st_size, fp))
-		chomp(*hostname);
+			chomp(*hostname);
 		fclose(fp);
 	}
 
 done:
 	if (*hostname)
-		sethostname(*hostname, strlen(*hostname));
+		(void)sethostname(*hostname, strlen(*hostname));
 }
 
 /*

src/serv.c

@@ -58,7 +58,9 @@ static void do_list(const char *path)
 	glob_t gl;
 	size_t i;
 
-	chdir(path);
+	if (chdir(path))
+		return;
+
 	if (glob("*.conf", 0, NULL, &gl))
 		return;
 
@@ -213,7 +215,7 @@ int do_disable(char *arg, int check)
 
 	if (chdir(FINIT_RCSD))
 		err(1, "failed cd %s", FINIT_RCSD);
-	chdir("enabled");	   /* System *may* have enabled/ dir. */
+	(void)chdir("enabled");	   /* System *may* have enabled/ dir. */
 
 	if (check && stat(arg, &st))
 		errx(1, "%s not (an) enabled (service).", arg);

src/service.c

@@ -464,17 +464,18 @@ static int service_start(svc_t *svc)
 
 		/* Set desired user+group */
 		if (gid >= 0)
-			setgid(gid);
+			(void)setgid(gid);
 
 		if (uid >= 0) {
-			setuid(uid);
+			(void)setuid(uid);
 
 			/* Set default path for regular users */
 			if (uid > 0)
 				setenv("PATH", _PATH_DEFPATH, 1);
 			if (home) {
 				setenv("HOME", home, 1);
-				chdir(home);
+				if (chdir(home))
+					(void)chdir("/");
 			}
 		}
 

src/utmp-api.c

@@ -97,7 +97,7 @@ static int logrotate(char *file, int num, off_t sz)
 			(void)rename(file, nfile);
 			create(file, st.st_mode, st.st_uid, st.st_gid);
 		} else {
-			truncate(file, 0);
+			(void)truncate(file, 0);
 		}
 	}