CODEWITHSUNDEEP
cdebuggingcoredump
Joshua Swink
Joshua Swink

Reputation: 3450

How can a C program produce a core dump of itself without terminating?

I want a C program to produce a core dump under certain circumstances. This is a program that runs in a production environment and isn't easily stopped and restarted to adjust other kinds of debugging code. Also, since it's in a production environment, I don't want to call abort(). The issues under investigation aren't easily replicated in a non-production environment. What I'd like is for the program, when it detects certain issues, to produce a core dump on its own, preferably with enough information to rename the file, and then continue.

Upvotes: 32

Views: 15351

Answers (5)

Ana Betts
Ana Betts

Reputation: 74654

void create_dump(void)
{
    if(!fork()) {
        // Crash the app in your favorite way here
        *((void*)0) = 42;
    }
}

Fork the process then crash the child - it'll give you a snapshot whenever you want

Upvotes: 61

Chris
Chris

Reputation: 4966

The source code to produce a core dump is in 'gcore', which is part of the gdb package.

Also, the Sun has gcore.

Also, you have to have a separate process running the core dump, as the current process must be suspended. You'll find the details in the gcore source, or you can just run your platform's gcore with your process as the target.

Upvotes: 2

njsf
njsf

Reputation: 2739

Do you really want a core, or just a stacktrace ? If all you want is a stacktrace you could take a look at the opensource here and try and integrate the code from there, or maybe just calling it from the command line is enough.

I believe some code in the gdb project might also be useful.

Another think you might want to do is to use gdb to attach to a running process.

$ gdb /path/to/exec 1234 # 1234 is the pid of the running process

Upvotes: 3

regnarg
regnarg

Reputation: 716

Another way might be to use the Google Coredumper library. This creates a similar result to the fork+abort technique but plays nicer with multithreaded apps (suspends all threads for a little while before forking so that they don't make a mess in the child).

Example:

    #include <google/coredumper.h>
    ...
    WriteCoreDump('core.myprogram');
    /* Keep going, we generated a core file,
     * but we didn't crash.
     */

Upvotes: 7

mat_geek
mat_geek

Reputation: 2511

Sun describes how to get a core file on Solaris, HP-UX, Redhat, and Windows here.

Solaris has the gcore program. HP-UX may have it. Otherwise use gdb and its gcore commmand. Windows has win-dbg-root\tlist.exe and win-dbg-root\adplus.vbs

Upvotes: 4

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