Why is the x86 undefined instruction called ud2?

T1Covered by 1 source · first reported by Raspberry Pi / Arduino / Adafruit at 28 Sept, 20:32 UTC

Raymond Chen, writing at The Old New Thing, explains the history behind the x86 instruction ud2. It is an architecturally undefined instruction that always raises an invalid opcode exception. Compilers emit it to mark unreachable code. If a function marked [[noreturn]] somehow returns, the compiler…

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Sources

• T1Why is the x86 undefined instruction called ud2?Raspberry Pi / Arduino / Adafruit28 Sept, 20:32