"wrong ELF class: ELFCLASS32"，但仅在使用 GDB 时

Question

我正在尝试在调试器中运行 dfhack。我运行的是 64 位 Ubuntu Trusty，但是 Dwarf Fortress 没有 64 位版本，所以我运行的是 32 位 Dwarf Fortress。我已经通过 apt-get install gdb:i386.

安装了 gdb

以下是我使用 gdb 启动 dfhack 时发生的情况：

ben@australium:~/df_linux$ xvfb-run -a ./dfhack --gdb
GNU gdb (Ubuntu 7.7.1-0ubuntu5~14.04.2) 7.7.1
Copyright (C) 2014 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 "i686-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./libs/Dwarf_Fortress...(no debugging symbols found)...done.
(gdb) start
Temporary breakpoint 1 at 0x804bdec
Starting program: /home/ben/df_linux/libs/Dwarf_Fortress 
ERROR: ld.so: object './hack/libdfhack.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/i386-linux-gnu/libthread_db.so.1".

Temporary breakpoint 1, 0xf7598b53 in main ()
   from /home/ben/df_linux/libs/libgraphics.so
(gdb)

以下是我在没有 gdb 的情况下运行它时发生的情况：

ben@australium:~/df_linux$ xvfb-run -a ./dfhack
Xlib:  extension "RANDR" missing on display ":99".
Loading bindings from data/init/interface.txt
New window size: 1280x720
Font size: 10x12
Resizing grid to 128x60
Resizing font to 10x12

Resetting textures
DFHack is ready. Have a nice day!
Type in '?' or 'help' for general help, 'ls' to see all commands.
[DFHack]#

可执行文件、预加载库和 gdb 都是 32 位的：

ben@australium:~/df_linux$ readelf -h /home/ben/df_linux/libs/Dwarf_Fortress
ELF Header:
  Magic:   7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00 
  Class:                             ELF32
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              EXEC (Executable file)
  Machine:                           Intel 80386
  Version:                           0x1
  Entry point address:               0x804c980
  Start of program headers:          52 (bytes into file)
  Start of section headers:          18192664 (bytes into file)
  Flags:                             0x0
  Size of this header:               52 (bytes)
  Size of program headers:           32 (bytes)
  Number of program headers:         8
  Size of section headers:           40 (bytes)
  Number of section headers:         28
  Section header string table index: 27
ben@australium:~/df_linux$ readelf -h /home/ben/df_linux/hack/libdfhack.so 
ELF Header:
  Magic:   7f 45 4c 46 01 01 01 03 00 00 00 00 00 00 00 00 
  Class:                             ELF32
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - GNU
  ABI Version:                       0
  Type:                              DYN (Shared object file)
  Machine:                           Intel 80386
  Version:                           0x1
  Entry point address:               0x1b7e40
  Start of program headers:          52 (bytes into file)
  Start of section headers:          43686636 (bytes into file)
  Flags:                             0x0
  Size of this header:               52 (bytes)
  Size of program headers:           32 (bytes)
  Number of program headers:         7
  Size of section headers:           40 (bytes)
  Number of section headers:         37
  Section header string table index: 34
ben@australium:~/df_linux$ readelf -h /usr/bin/gdb
ELF Header:
  Magic:   7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00 
  Class:                             ELF32
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              EXEC (Executable file)
  Machine:                           Intel 80386
  Version:                           0x1
  Entry point address:               0x808cb95
  Start of program headers:          52 (bytes into file)
  Start of section headers:          5089368 (bytes into file)
  Flags:                             0x0
  Size of this header:               52 (bytes)
  Size of program headers:           32 (bytes)
  Number of program headers:         9
  Size of section headers:           40 (bytes)
  Number of section headers:         28
  Section header string table index: 27

Answer 1

ERROR: ld.so: object './hack/libdfhack.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.

这个错误来自于 GDB 启动你的（64 位）shell，它反过来执行你的（32 位）dfhack 程序。

您应该只关心预加载到目标程序中。 libdfhack.so 没有预加载到您的 shell 中 没有任何后果，您应该忽略它。

"wrong ELF class: ELFCLASS32"，但仅在使用 GDB 时

"wrong ELF class: ELFCLASS32", but only when using GDB

linux

gdb

32bit-64bit