Code review comment for lp://staging/~kdub/mir/gbm-ext-v2

(Non-blocking)
+}
+catch (...)
+{
+ return INT64_MAX;
+}

Probably (slightly) safer to return 0 here - 0 means the contents are undefined, so the client will have to do more work but is guaranteed to render correctly.

Also, uint64_t? This is almost always going to have a range of 0-3, and cannot possibly go beyond the tens of thousands (buffers will be on the order of megabytes, we're definitely not going to give a client > 10GB of VRAM just for window buffers!)

Is there a reason you picked uint64_t rather than uint32_t?