GDB help to analyse core

Question

One of our code is generating a core file While trying to analyse core using gdb with below commands gdb programe_name core

I am unable to retrieve the tarce with backtrace command getting below

  #4  0x20202020 in ?? ()
  #5  0x20202020 in ?? ()
  #6  0x20202020 in ?? ()
  #7  0x20202020 in ?? ()
  #8  0x20202020 in ?? ()
  #9  0x20202020 in ?? ()
  #10 0x20202020 in ?? ()
  #11 0x20202020 in ?? ()
  #12 0x20202020 in ?? ()
  #13 0x20202020 in ?? ()
  #14 0x20202020 in ?? ()
  #15 0x20202020 in ?? () 
  #16 0x20202020 in ?? ()
  #17 0x20202020 in ?? ()
  #18 0x20202020 in ?? ()
  #19 0x20202020 in ?? ()

do we have a command which I can use to get trace with function name and arguments

Are you using a cross compiler? If yes did you setup set solib-absolute-prefix and solib-search-path ? — Tectrendz, Feb 19 '17 at 23:42

score 3 · Accepted Answer · edited May 23 '17 at 12:31

It looks like your stack has been "crunched" -- that is, overwritten with some data that shouldn't be there.

0x20202020 is four spaces in ASCII, so the stack has been overwritten by a string of characters with a lot of spaces.

Look for an array (or variable) that you are reading into (or copying characters into); the chances are you are reading/copying more data than you expected into that array/variable.

To avoid this sort of thing in the future, use one of the forms that allows you to limit the amount read/copied to the size of the target area:

fread
fgets
strncpy

You might want to also take a look at the answers to Reading in a variable length string user input in C As relatively safe ways to protect yourself when reading data of unknown length into a buffer.

GDB help to analyse core

1 Answers1