Raymond Chen explains why x86 provides a dedicated ud2 instruction rather than relying on int 6 to generate invalid opcode exceptions. The key difference is that ud2 is a fault, reporting the faulting instruction's address to the exception handler, while int 6 is a trap, reporting the address of the following instruction. This distinction matters for exception handling, debugging, and signal delivery.
Background
Raymond Chen's column explores lesser-known details of Windows and x86 architecture. The ud2 instruction is commonly used by compilers to signal unimplemented code paths or runtime assertions.
- Source
- Lobsters
- Published
- Oct 21, 2026 at 04:43 AM
- Score
- 5.0 / 10