Heretic/Hexen: Skipping through maps while recording causes Segfault

[Noseey]

Background

Version of Crispy Doom: at least since 7.0.0 (Heretic) up until master 22.05.2026, haven't tried older releases.

Operating System and version: Windows 11

Game: Heretic / Hexen

Any loaded WADs and mods (please include full command line): -

Bug description

Skipping through maps using the Go-to-next-Level button in Heretic and Hexen while demo recording leads to a crash to desktop. It works best when holding down the button and after a few dozens of maps, the segfault usually occurs.

Observed behavior:
Segfault Hexen (x being Null)

Call Stack Hexen:

It does not always crash at this specific location, sometimes e. g. line->v2->x was empty. Occasionally, graphical glitches start appearing a few maps before the crash happens.

Expected behavior:
It should not crash, even though this requires very specific prerequisites. But it makes it a low priority issue.

[fabiangreffrath]

And this only happens during demo recording? That's strange...

[fabiangreffrath]

Could you try to trigger this again when the engine is built with the native allocator?

[Noseey]

And this only happens during demo recording? That's strange...

At least, I could not reproduce it without the recording. But I would not rule out completely that the recording is just an accelerator for an underlying (memory) issue.

Could you try to trigger this again when the engine is built with the native allocator?

I did just test it with z_native.c but it crashes aswell in the same fashion.

[fabiangreffrath]

Try turning "uncapped framerate" to "off". 😉

[fabiangreffrath]

Apparently, we still have vissprites from the previous map in the rendering pipeline while loading the new level.

[Noseey]

Try turning "uncapped framerate" to "off". 😉

I also tried this, but unfortunately to no avail.

Since it only seems to happen during demo-recording, I decided to move the recording start from the DeferedInitNew into the actual G_DoInitNew:

void G_DoInitNew(void)
{
    SV_InitBaseSlot();
    // [crispy] if a new game is started during demo recording, start a new demo
    if (demorecording)
    {
        G_CheckDemoStatus();
        Z_Free(demoname);
        G_RecordDemo(TempSkill, 1, TempEpisode, TempMap, orig_demoname);
    }
    else
        G_InitNew(TempSkill, TempEpisode, TempMap);
    gameaction = ga_nothing;
}

.. and on a first glance, this seems to resolve the issue (also for Heretic, moving it into G_DoNewGame accordingly), while still performing the recording correctly. But so far, I can not pin point exactly, why it works. Will need to have a further look on it and hope it is not just a symptom treatment. 😀

Apparently, we still have vissprites from the previous map in the rendering pipeline while loading the new level.

Is there a good way to debug this?