reduce thread-unsafe use of static variables

- rework ip_ntoa() to avoid use of static variables
- rework sort_client_list() to avoid use of static variables
- move static 'lastdump' into Messenger struct
- rework ID2String() to avoid use of static variables; rename to id_to_string()
- fetch_broadcast_info(): attempt to mitigate risks from concurrent execution
- current_time_monotonic(): attempt to mitigate risks from concurrent execution
- comment on non-thread-safety of unix_time_update

1 files changed, 2 insertions, 0 deletions

diff --git a/toxcore/util.c b/toxcore/util.c
index e1bbf4db..22fa0fc9 100644
--- a/toxcore/util.c
+++ b/toxcore/util.c
@@ -41,6 +41,8 @@
 static uint64_t unix_time_value;
 static uint64_t unix_base_time_value;
 
+/* XXX: note that this is not thread-safe; if multiple threads call unix_time_update() concurrently, the return value of
+ * unix_time() may fail to increase monotonically with increasing time */
 void unix_time_update(void)
 {
     if (unix_base_time_value == 0) {