Invalid register eip?

Question

I am debugging a c program with gdb in linux terminal, I disassembled it and ran it, then tried to find the memory address the the EIP register. This is what happened:

(gdb) i r eip Invalid register `eip'

Why does it say that my eip register is invalid?

Answer 1

Is it a 64-bit program? If so, it's rip, not eip.

Answer 2

Depending on your program's architecture the register can change:

• 16 bit - ip
• 32 bit - eip
• 64 bit - rip