Member Avatar for RohitSahni

Why we get the core file and also how can we debug it in unix(using sun C++ compiler)

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Core files are a snapshot of a process (memory + registers) written when the program is terminated by a fatal condition (segfault, abort/assert, illegal instruction, divide-by-zero, bus error, etc.). As pointed out, their existence means the program hit an abnormal runtime condition; the core lets a debugger show exactly where and what state led to that condition.

Make cores usable

  • Ensure the shell will create them:

    # sh/ksh/bash
ulimit -c unlimited

# csh/tcsh
limit coredumpsize unlimited

  • Compile with debug symbols and without optimization so frames and locals are visible:

    CC -g -o myprog myprog.cpp

    Do not strip the binary; verify with file myprog.

Quick debugging workflow

  • A quick stack-only snapshot tool (as suggested) is useful for triage.

  • For full inspection, run a debugger against the executable and the core:

    # gdb
gdb myprog core
(gdb) bt
(gdb) frame 0
(gdb) print someVar

# dbx (Solaris)
dbx myprog core
(dbx) where
(dbx) frame 0
(dbx) print someVar

Practical tips and gotchas

  • If no core appears, check ulimit, setuid/setgid restrictions, file permissions, available disk space, and any OS core configuration (system utilities or kernel settings can redirect/disable cores).
  • Optimization can hide or inline frames; rebuild without optimizations if line-accurate traces are needed.
  • Core files can be large and contain secrets (stack contents, passwords); treat them as sensitive before sharing.

This fills out the short answers in the thread: use a quick stack tool for triage, but for definitive diagnosis build with -g and debug the core in dbx/gdb to inspect frames, locals and the failing instruction.

Recommended Answers

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Member Avatar for Ancient Dragon

>>Why we get the core file
Because you made errors in the program.

>>how can we debug it in unix
tutorial

Member Avatar for Agni

use >pstack core

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