[BUG] Saving the game in multiplayer while one session's renderer isn't fully initialized causes that session to crash

[zhs2]

GZDoom version

GZDoom 4.13.2

Which game are you running with GZDoom?

Doom 2

What Operating System are you using?

Windows 10

Please describe your specific OS version

No response

Relevant hardware info

No response

Have you checked that no other similar issue already exists?

• I have searched and not found similar issues.

A clear and concise description of what the bug is.

Running two multiplayer sessions on a single machine and not focusing one of those sessions causes that session to crash when the session that has been focused at least once attempts to save. My uninformed suspicion is that this is due to the PNG writer not having valid data to work with when creating a save file.

Steps to reproduce the behaviour.

Explain how to reproduce

1. -host 2 and -join localhost on the same computer
2. Save the game in one of these sessions the immediate moment you are in-game, do NOT alt-tab between them
3. The other session will immediately crash, causing multiplayer to briefly hang

Your configuration

No response

Provide a Log

CrashReport.zip

[RicardoLuis0]

My uninformed suspicion is that this is due to the PNG writer not having valid data to work with when creating a save file.

the PNG writer uses the screenshot buffer, which is set when rendering, so most likely yeah

[Boondorl]

I've noticed this issue before alongside saves failing in the serializer itself, likely due to the inability to access the save file since both instances are fighting for it. Honestly, I think the best strategy here would be to disable all clients on the same machine trying to save and only have the first one to receive the command do so, but I don't know what the best strategy to handle this would be.