Dtrace was implemented under Solaris 8, which ironicly ironically did not support dtrace. Instead, a version of dtrace was hacked into the Sun's (now
Oracle's) build machines. This dtrace version supported an early version of the USDT user space dtrace probes that I'll call USDT1.
When Apple introduced dtrace into its Leopard OS, it used a later version of Sun's dtrace that has a different probe style. Oracle has
not been able to move to the newer probe style because it still has builds that require the older versions of Solaris.
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