用gdb 檢視彙編程式碼， 採用disassemble 和 x 命令。 nexti, stepi 可以單步指令執行

如下例：

------------------------------------------------------------
原始碼：
------------------------------------------------------------
[root@hjj ~]# cat 1.c
#include <stdio.h>

int main(int argc, char *argv[])
{
    int size=sizeof("hjj");
    printf("size is %d\n",size);
    return 0;
}

------------------------------------------------------------
編譯
------------------------------------------------------------
ot@hjj ~]# gcc -g3 -o 1 1.c

------------------------------------------------------------
除錯
------------------------------------------------------------
[root@hjj ~]# gdb 1
GNU gdb (GDB) 7.6
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-unknown-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /root/1...done.
(gdb) b main
Breakpoint 1 at 0x4004d3: file 1.c, line 5.
(gdb) r
Starting program: /root/1

Breakpoint 1, main (argc=1, argv=0x7fffffffe5c8) at 1.c:5
5        int size=sizeof("hjj");

------------------------------------------------------------

觀察. 用disasseble.

/m 原始碼和彙編一起排列

/r 還可以看到16進位制程式碼

------------------------------------------------------------
(gdb) disassemble /m main
Dump of assembler code for function main:
4    {
   0x00000000004004c4 <+0>:    push   %rbp
   0x00000000004004c5 <+1>:    mov    %rsp,%rbp
   0x00000000004004c8 <+4>:    sub    $0x20,%rsp
   0x00000000004004cc <+8>:    mov    %edi,-0x14(%rbp)
   0x00000000004004cf <+11>:    mov    %rsi,-0x20(%rbp)

5        int size=sizeof("hjj");
=> 0x00000000004004d3 <+15>:    movl   $0x4,-0x4(%rbp)

6        printf("size is %d\n",size);
   0x00000000004004da <+22>:    mov    $0x4005f8,%eax
   0x00000000004004df <+27>:    mov    -0x4(%rbp),%edx
   0x00000000004004e2 <+30>:    mov    %edx,%esi
   0x00000000004004e4 <+32>:    mov    %rax,%rdi
   0x00000000004004e7 <+35>:    mov    $0x0,%eax
   0x00000000004004ec <+40>:    callq  0x4003b8 <printf@plt>

7        return 0;
   0x00000000004004f1 <+45>:    mov    $0x0,%eax

8    }
   0x00000000004004f6 <+50>:    leaveq
   0x00000000004004f7 <+51>:    retq   

End of assembler dump.
------------------------------------------------------------
用 x/i 可以檢視指令
------------------------------------------------------------
(gdb) x/15i main
   0x4004c4 <main>:    push   %rbp
   0x4004c5 <main+1>:    mov    %rsp,%rbp
   0x4004c8 <main+4>:    sub    $0x20,%rsp
   0x4004cc <main+8>:    mov    %edi,-0x14(%rbp)
   0x4004cf <main+11>:    mov    %rsi,-0x20(%rbp)
=> 0x4004d3 <main+15>:    movl   $0x4,-0x4(%rbp)
   0x4004da <main+22>:    mov    $0x4005f8,%eax
   0x4004df <main+27>:    mov    -0x4(%rbp),%edx
   0x4004e2 <main+30>:    mov    %edx,%esi
   0x4004e4 <main+32>:    mov    %rax,%rdi
   0x4004e7 <main+35>:    mov    $0x0,%eax
   0x4004ec <main+40>:    callq  0x4003b8 <printf@plt>
   0x4004f1 <main+45>:    mov    $0x0,%eax
   0x4004f6 <main+50>:    leaveq
   0x4004f7 <main+51>:    retq   
------------------------------------------------------------
$pc 指向當前程式執行地址
------------------------------------------------------------
(gdb) x/5i $pc
=> 0x4004d3 <main+15>:    movl   $0x4,-0x4(%rbp)
   0x4004da <main+22>:    mov    $0x4005f8,%eax
   0x4004df <main+27>:    mov    -0x4(%rbp),%edx
   0x4004e2 <main+30>:    mov    %edx,%esi
   0x4004e4 <main+32>:    mov    %rax,%rdi
(gdb)
--------------------------------------------------------------------------------
用gdb 除錯彙編程式碼（二進位制程式碼).
檢視:
disassembler $pc
display/i $pc
x/i $pc
執行: 單指令。
ni;
si:

用 p $eax

p $edi 等可以檢視暫存器.

在gdb中 敲入help layout

(gdb) help layout
Change the layout of windows.
Usage: layout prev | next | <layout_name>
Layout names are:
   src   : Displays source and command windows.
   asm   : Displays disassembly and command windows.
   split : Displays source, disassembly and command windows.
   regs  : Displays register window. If existing layout
           is source/command or assembly/command, the
           register window is displayed. If the
           source/assembly/command (split) is displayed,
           the register window is displayed with
           the window that has current logical focus.

然後你可以用layout 去除錯,很方便, 例如 layout asm.