gdb executable file format

Question

I'm trying to use GDB to debug (to find an annoying segfault). When I run:

gdb ./filename

from the command line, I get the following error:

This GDB was configured as "i686-pc-linux-
gnu"..."/path/exec": not in executable 
format: File format not recognized

When I execute:

file /path/executable/

I get the following info:

 ELF 64-bit LSB executable, AMD x86-64,
 version 1 (SYSV), for GNU/Linux 2.4.0, 
 dynamically linked (uses shared libs), not stripped

I am using GDB 6.1, and the executable is compiled with gcc version 3.4.6.

I'm a little out of my water in terms of using gdb, but as far as I can tell it should be working in this instance. Any ideas what's going wrong?

Answer 1

The executable is 64-bit (x86-64) and the debugger is a 32 bit (i686-pc-linux) build. You may need to install a 64-bit (x86-64) version of the debugger.

Answer 2

The question refers to "./filename" and to "/path/executable". Are these the same file?

If you are doing a post-mortem analysis, you would run:

gdb executable-file core-file

If you are going to ignore the core file, you would run:

gdb executable-file

In both cases, 'executable-file' means a pathname to the binary you want to debug. Most usually, that is actually a simple filename in the current directory, since you have the source code from your debug build there.

On Solaris, a 64-bit build of GDB is supposed to be able to debug both 32-bit and 64-bit executables (though I've had some issues with recent versions of GDB). I'm not sure of the converse - that a 32-bit GDB can necessarily debug 64-bit executables.

Answer 3

I'm not sure if this is your problem, but I faced this situation very often. The executable in the build tree, build by make/automake is not a binary, but a script, so you cannot use gdb with it. Try to install the application and change the directory, because else gdb tries to debug the script.

Answer 4

What you need to be checking, is really the bfd library. The binary file descriptor library is what binutils / gdb uses to actually parse and handle binaries (ELF/a.out etc..).

You can see the current supported platforms via objdump;

# objdump -H

objdump: supported targets: elf32-powerpc aixcoff-rs6000 elf32-powerpcle ppcboot elf64-powerpc elf64-powerpcle elf64-little elf64-big elf32-little elf32-big srec symbolsrec tekhex binary ihex
objdump: supported architectures: rs6000:6000 rs6000:rs1 rs6000:rsc rs6000:rs2 powerpc:common powerpc:common64 powerpc:603 powerpc:EC603e powerpc:604 powerpc:403 powerpc:601 powerpc:620 powerpc:630 powerpc:a35 powerpc:rs64ii powerpc:rs64iii powerpc:7400 powerpc:e500 powerpc:MPC8XX powerpc:750

The following PPC specific disassembler options are supported for use with
the -M switch:
  booke|booke32|booke64    Disassemble the BookE instructions
  e300                     Disassemble the e300 instructions
  e500|e500x2              Disassemble the e500 instructions
  efs                      Disassemble the EFS instructions
  power4                   Disassemble the Power4 instructions
  power5                   Disassemble the Power5 instructions
  power6                   Disassemble the Power6 instructions
  32                       Do not disassemble 64-bit instructions
  64                       Allow disassembly of 64-bit instructions