Safety check to prevent crash on macOS when IOHIDManagerCopyDevices() returns NULL #359
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I have seen several crashes on macOS 10.12.6 caused by the fact that IOHIDManagerCopyDevices() returned NULL. Calling CFSetGetCount() on a NULL CFSetRef causes a crash. The fix consists of checking if the CFSetRef is not NULL before using it. Here is a backtrace of a crash:
0x00007fffd04a5118 CFSetGetCount + 24
0x000000010c15147f hid_enumerate (hid.c:427)
0x000000010c151acc hid_open (hid.c:529)