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  • [gentoo-user] How do I get a core dump from seg-faulting software?

    From Alan Mackenzie@21:1/5 to All on Thu Dec 16 17:10:01 2021
    Hello, Gentoo.

    I'm developing software, and it crashes in its build process. I want a
    core dump, to help find out where and why it's crashing.

    I've got CONFIG_ELF_CORE and CONFIG_COREDUMP both configured to yes in
    my kernel.

    When I do

    $ uclimit -H -c

    , it tells me "unlimited".

    But still, no dump. :-(

    What am I missing?

    --
    Alan Mackenzie (Nuremberg, Germany).

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From karl@aspodata.se@21:1/5 to All on Thu Dec 16 17:40:02 2021
    Alex:
    I've got CONFIG_ELF_CORE and CONFIG_COREDUMP both configured to yes in
    my kernel.

    When I do

    $ uclimit -H -c

    , it tells me "unlimited".

    But still, no dump. :-(

    What am I missing?

    Have you tried:

    $ man gcore
    $ man 5 core

    Regards,
    /Karl Hammar

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Rich Freeman@21:1/5 to acm@muc.de on Thu Dec 16 21:30:01 2021
    On Thu, Dec 16, 2021 at 10:55 AM Alan Mackenzie <acm@muc.de> wrote:

    But still, no dump. :-(

    What am I missing?

    Are you using systemd? It has a mechanism to consolidate core dumps
    to a system directory with a tool to view/debug them and retention
    policies. I think that all is enabled by default, but it has been a
    while since I touched it. If it is enabled then that might explain
    why dumps aren't where you expect them.

    --
    Rich

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From tastytea@21:1/5 to acm@muc.de on Fri Dec 17 00:20:02 2021
    On 2021-12-16 15:55+0000 Alan Mackenzie <acm@muc.de> wrote:

    Hello, Gentoo.

    I'm developing software, and it crashes in its build process. I want
    a core dump, to help find out where and why it's crashing.

    I've got CONFIG_ELF_CORE and CONFIG_COREDUMP both configured to yes in
    my kernel.

    When I do

    $ uclimit -H -c

    , it tells me "unlimited".

    But still, no dump. :-(

    What am I missing?


    You need to enable them explicitly. If you're using PAM:
    echo '* soft core unlimited' > /etc/security/limits.conf

    It only has an effect after your next login. For more information, see <https://wiki.gentoo.org/wiki/Project:Quality_Assurance/Backtraces#Core_dumps>.

    Kind regards, tastytea

    --
    Get my PGP key with `gpg --locate-keys tastytea@tastytea.de` or at <https://tastytea.de/tastytea.asc>.

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    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Alan Mackenzie@21:1/5 to Rich Freeman on Fri Dec 17 12:30:01 2021
    Hello, Rich.

    On Thu, Dec 16, 2021 at 15:23:53 -0500, Rich Freeman wrote:
    On Thu, Dec 16, 2021 at 10:55 AM Alan Mackenzie <acm@muc.de> wrote:

    But still, no dump. :-(

    What am I missing?

    Are you using systemd? It has a mechanism to consolidate core dumps
    to a system directory with a tool to view/debug them and retention
    policies. I think that all is enabled by default, but it has been a
    while since I touched it. If it is enabled then that might explain
    why dumps aren't where you expect them.

    No, I'm on openrc. I think tastytea's answer will work.

    Thanks!

    --
    Rich

    --
    Alan Mackenzie (Nuremberg, Germany).

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Alan Mackenzie@21:1/5 to tastytea on Fri Dec 17 12:30:01 2021
    Hello, tastytea.

    On Fri, Dec 17, 2021 at 00:18:12 +0100, tastytea wrote:
    On 2021-12-16 15:55+0000 Alan Mackenzie <acm@muc.de> wrote:

    Hello, Gentoo.

    I'm developing software, and it crashes in its build process. I want
    a core dump, to help find out where and why it's crashing.

    I've got CONFIG_ELF_CORE and CONFIG_COREDUMP both configured to yes in
    my kernel.

    When I do

    $ uclimit -H -c

    , it tells me "unlimited".

    But still, no dump. :-(

    What am I missing?


    You need to enable them explicitly. If you're using PAM:
    echo '* soft core unlimited' > /etc/security/limits.conf

    It only has an effect after your next login. For more information, see <https://wiki.gentoo.org/wiki/Project:Quality_Assurance/Backtraces#Core_dumps>.

    Thanks greatly! This was a very helpful answer. I've now edited that
    file, and will be ready next time there's a problem like this.

    As half expected when you ask a question like this, I found the problem
    in my build software anyhow. I was doing one too many pointer
    dereferences on a (in C) **bool.

    Kind regards, tastytea

    --
    Get my PGP key with `gpg --locate-keys tastytea@tastytea.de` or at <https://tastytea.de/tastytea.asc>.

    --
    Alan Mackenzie (Nuremberg, Germany).

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Alan Mackenzie@21:1/5 to karl@aspodata.se on Fri Dec 17 12:30:01 2021
    Hello, Karl.

    On Thu, Dec 16, 2021 at 17:32:58 +0100, karl@aspodata.se wrote:
    Alex:
    I've got CONFIG_ELF_CORE and CONFIG_COREDUMP both configured to yes in
    my kernel.

    When I do

    $ uclimit -H -c

    , it tells me "unlimited".

    But still, no dump. :-(

    What am I missing?

    Have you tried:

    $ man gcore
    $ man 5 core

    I've looked at them now, thanks. It was tastytea who spotted the crux,
    the file /etc/security/limits.conf.

    Regards,
    /Karl Hammar

    --
    Alan Mackenzie (Nuremberg, Germany).

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)