config_libconfig: fix xdgConfigDirectories

Fixed 2 problems:

1. Made sure the returned list is NULL terminated.
2. Allocate the duplicated string and the return list together, so the
   duplicated string will be freed as we free the list. Fixed a memory
   leak.

Fixes #324

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/config_libconfig.c

@@ -53,26 +53,34 @@ const char *xdgConfigHome(void) {
 }
 
 const char * const * xdgConfigDirectories(void) {
-	char *dirs, *path, *xdgd = getenv("XDG_CONFIG_DIRS");
-	char **dir_list = {0};
-	unsigned int sep = 0;
+	char *xdgd = getenv("XDG_CONFIG_DIRS");
+	size_t count = 0;
 
-	if (!xdgd) xdgd = ":/etc/xdg:";
-
-	dirs = strdup(xdgd);
-	CHECK(dirs != NULL);
-	path = strtok(dirs, ":");
-
-	while (path) {
-		dir_list = realloc(dir_list, sizeof(char*) * ++sep);
-
-		CHECK(dir_list);
-
-		dir_list[sep-1] = path;
-
-		path = strtok(NULL, ":");
+	if (!xdgd) {
+		xdgd = "/etc/xdg";
 	}
 
+	for (int i = 0; xdgd[i]; i++) {
+		if (xdgd[i] == ':') {
+			count++;
+		}
+	}
+
+	// Store the string and the result pointers together so it can be
+	// freed together
+	char **dir_list = cvalloc(sizeof(char *) * (count + 2) + strlen(xdgd) + 1);
+	auto dirs = strcpy((char *)dir_list + sizeof(char *) * (count + 2), xdgd);
+	auto path = dirs;
+
+	for (size_t i = 0; i < count; i++) {
+		dir_list[i] = path;
+		path = strchr(path, ':');
+		*path = '\0';
+		path++;
+	}
+	dir_list[count] = path;
+	dir_list[count + 1] = NULL;
+
 	return (const char * const *)dir_list;
 }