CODEWITHSUNDEEP
gdb
Mishti
Mishti

Reputation: 47

GDB help to analyse core

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

Upvotes: 0

Views: 331

Answers (1)

A. P. Damien
A. P. Damien

Reputation: 386

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.

Upvotes: 3

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