How I can generate undefined instruction exception in C language

void undef(void)
{
    static const int instr = 0x12345678; /* fake undefined opcode */
    ((void(*)(void))&instr)();
}

But you'll have to come up with a real undefined opcode. 0x12345678 won't do it.

void undef(void)
{
    static const int instr = 0x12345678; /* fake undefined opcode */
    ((void(*)(void))&instr)();
}

But you'll have to come up with a real undefined opcode. 0x12345678 won't do it.