test instruction +

| GDB shows TEST instruction | Dump of assembler code for function *__GI___poll: 0x00007f73ec2120b0 : sub $0x28,%rsp 0x00007f73ec2120b4 : mov 0x29c52e(%rip),%eax # 0x7f73ec4ae5e8 0x00007f73ec2120ba : test %eax,%eax 0x00007f73ec2120bc : jne 0x7f73ec2120d5 0x00007f73ec2120be : movslq %edx,%rdx 0x00007f73ec2120c1 : mov $0x7,%eax 0x00007f73ec2120c6 : syscall 0x00007f73ec2120c8 : cmp $0xfffffffffffff000,%rax 0x00007f73ec2120ce : ja 0x7f73ec212121 0x00007f73ec2120d0 : add $0x28,%rsp 0x00007f73ec2120d4 …

Jump if Equal :)

je instruction (gdb) disass Dump of assembler code for function fputs_unlocked: 0xb7788c30 : push %ebp 0xb7788c31 : mov %esp,%ebp 0xb7788c33 : sub $0x1c,%esp 0xb7788c36 : mov %ebx,-0xc(%ebp) 0xb7788c39 : call 0xb773daaf 0xb7788c3e : add $0xe13b6,%ebx 0xb7788c44 : mov %edi,-0x4(%ebp) => 0xb7788c47 : mov 0x8(%ebp),%edi 0xb7788c4a : mov %esi,-0x8(%ebp) 0xb7788c4d : mov 0xc(%ebp),%esi 0xb7788c50 : mov …