How to get instruction information from libopcodes?

Question

I am writing a tool which uses libbfd and libopcodes in x86-32 and x86-64 Linux to perform disassembly. The problem is that whilst I am able to get

Answer 1

Libopcodes prints disassembled instructions into the stream which is intercepted by your custom_printf function. Your mistake is that you assume that custom_printf is called once each time a single instruction is disassembled, however, it is called more often, particularly, to print each mnemonic,operand, address or separator.

So, resulting disassembly of your binary is

xor %ebp, %ebp

mov %rdx, %r9

pop %rsi

mov %rsp, %rdx

and $0xfffffffffffffff0, %rsp

push %rax

push %rsp

mov $0x401450,%r8

...