[BUG]: Sven Co-op 5.26 Linux dedicated server occasionally segfaults on map change

[NHellFire]

👉👈 Contact Details (optional)

No response

🤔 What happened?

svends occasionally segfaults on map change. Coredump from a debug build shows a null pointer:

Core was generated by `./svends_i686 -game svencoop -strictportbind +ip 94.XX.XX.XX -port 27015 +clientport 27005 +map svencoop1 +servercfgfile svenserver.cfg +maxplayers 16 -insecure -debug +sv_cheats 2 -pidfile svends.4051776.pid'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0xdfdd774b in meta_collect_fix_data (esp=0xf727c3c0, data=...) at /src/Metamod-R/metamod/src/metamod.cpp:461
461             do pret--;
(gdb) bt 6
#0  0xdfdd774b in meta_collect_fix_data (esp=0xf727c3c0, data=std::vector of length 1, capacity 1 = {...}) at /src/Metamod-R/metamod/src/metamod.cpp:461
#1  0xdfdd780d in meta_collect_fix_data (esp=0xfffdc688, data=std::vector of length 1, capacity 1 = {...}) at /src/Metamod-R/metamod/src/metamod.cpp:500
#2  0xdfdd78a2 in meta_rebuild_callbacks () at /src/Metamod-R/metamod/src/metamod.cpp:532
#3  0xdfdd8e1f in MPluginList::refresh (this=0x57063fa0, now=PT_CHANGELEVEL) at /src/Metamod-R/metamod/src/mlist.cpp:563
#4  0xdfdd458a in mm_ServerDeactivate () at /src/Metamod-R/metamod/src/dllapi.cpp:61
#5  0xf61e0792 in ?? () from /home/gameservers/Games/steam/svencoop/serverfiles/engine_i686.so
(gdb) x pret
0xe3240000:     0x00000000

For debugging, I'm using my own build of metamod, which is rehlds/Metamod-R@1.3.0.149 with only this change:

diff --git a/metamod/CMakeLists.txt b/metamod/CMakeLists.txt
index 18d46fc..b82d26e 100644
--- a/metamod/CMakeLists.txt
+++ b/metamod/CMakeLists.txt
@@ -38 +38 @@ set(COMPILE_FLAGS "-m32 -U_FORTIFY_SOURCE")
-set(LINK_FLAGS "-m32 -s")
+set(LINK_FLAGS "-m32")

And built using:

./build.sh -c=gcc -j=$(nproc) -DDEBUG=ON -DCMAKE_BUILD_TYPE=COMPAT_GLIBC

⚠️ Meta-information

OS: Debian 13.3 (amd64)

Engine and metamod version info:

version; game version; meta version; meta list
Protocol version 48
Engine version 5.0.1.8 (svencoop)
Engine build: 19:37:07 Dec  5 2024 (10269)
Metamod-r v1.3.0.149+m, API (5:13)
Metamod-r build: 00:33:54 Jan 26 2026
Metamod-r from: https://github.com/rehlds/Metamod-R/commit/603a257
Currently loaded plugins:
      description  stat pend  file                vers          src  load  unload
 [ 1] AMX Mod X    RUN   -    amxmodx_mm_i386.so  v1.10.0.5474  ini  Start ANY
1 plugins, 1 running


AMXX version info:

amxx version; amxx plugins
AMX Mod X 1.10.0.5474 (http://www.amxmodx.org)
Authors:
        David "BAILOPAN" Anderson, Pavol "PM OnoTo" Marko
        Felix "SniperBeamer" Geyer, Jonny "Got His Gun" Bergstrom
        Lukasz "SidLuke" Wlasinski, Christian "Basic-Master" Hammacher
        Borja "faluco" Ferrer, Scott "DS" Ehlert
Compiled: Dec  1 2025 07:49:57
Built from: https://github.com/alliedmodders/amxmodx/commit/0c31b61
Build ID: 5474:0c31b61
Core mode: JIT+ASM32
Currently loaded plugins:
       id  name                    version     author            url                              file         status
 [  1] 0   Admin Base              1.10.0.547  AMXX Dev Team                                      admin.amxx   running
 [  2] 1   Admin Commands          1.10.0.547  AMXX Dev Team                                      admincmd.am  running
 [  3] 2   Admin Help              1.10.0.547  AMXX Dev Team                                      adminhelp.a  running
 [  4] 3   Slots Reservation       1.10.0.547  AMXX Dev Team                                      adminslots.  running
 [  5] 4   Multi-Lingual System    1.10.0.547  AMXX Dev Team                                      multilingua  running
 [  6] 5   Menus Front-End         1.10.0.547  AMXX Dev Team                                      menufront.a  running
 [  7] 6   Commands Menu           1.10.0.547  AMXX Dev Team                                      cmdmenu.amx  running
 [  8] 7   Players Menu            1.10.0.547  AMXX Dev Team                                      plmenu.amxx  running
 [  9] 8   Maps Menu               1.10.0.547  AMXX Dev Team                                      mapsmenu.am  running
 [ 10] 9   Plugin Menu             1.10.0.547  AMXX Dev Team                                      pluginmenu.  running
 [ 11] 10  Admin Chat              1.10.0.547  AMXX Dev Team                                      adminchat.a  running
 [ 12] 11  Anti Flood              1.10.0.547  AMXX Dev Team                                      antiflood.a  running
 [ 13] 12  Admin Votes             1.10.0.547  AMXX Dev Team                                      adminvote.a  running
 [ 14] 13  NextMap                 1.10.0.547  AMXX Dev Team                                      nextmap.amx  running
 [ 15] 14  Nextmap Chooser         1.10.0.547  AMXX Dev Team                                      mapchooser.  running
 [ 16] 15  TimeLeft                1.10.0.547  AMXX Dev Team                                      timeleft.am  running
 [ 17] 16  Pause Plugins           1.10.0.547  AMXX Dev Team                                      pausecfg.am  running
 [ 18] 17  Stats Configuration     1.10.0.547  AMXX Dev Team                                      statscfg.am  running
18 plugins, 18 running

📄 Relevant log output

L 26/01/2026 - 14:42:10: Changing to level "afrikakorps1".
L 26/01/2026 - 14:42:10: [META] ini: Begin re-reading plugins list: /home/gameservers/Games/steam/svencoop/serverfiles/svencoop/addons/metamod/plugins.ini
L 26/01/2026 - 14:42:10: [META] ini: Read plugin config for: AMX Mod X
L 26/01/2026 - 14:42:10: [META] ini: Finished reading plugins list: /home/gameservers/Games/steam/svencoop/serverfiles/svencoop/addons/metamod/plugins.ini; Found 1 plugins
L 26/01/2026 - 14:42:10: [META] dll: Updating plugins...
L 26/01/2026 - 14:42:10: [META] (debug:1) Keeping plugin 'AMX Mod X'
L 26/01/2026 - 14:42:10: [META] dll: Finished updating 1 plugins; kept 1, loaded 0, unloaded 0, reloaded 0, delayed 0
L 26/01/2026 - 14:42:10: [META] dll: Begin scan to collect callback fix data...
./svends_run: line 440: 4051805 Segmentation fault      (core dumped) $GAME_BIN_CMD
Uh oh it seems the server has crashed or failed to run (╯°□°）╯︵ ┻━┻
Support available on our Discord server: https://discord.gg/svencoop
Mon 26 Jan 14:42:12 GMT 2026: Server restart in 10 seconds

[autisoid]

Same here. Works OK for a random number of level changes, then eventually crashes:

Start Line: ./hlds_linux -port 42069 -game svencoop +log on +map _server_start +as_log_level 3 +developer 1 +maxplayers 32
[New LWP 288086]
[New LWP 288096]
[New LWP 288102]
[New LWP 288091]
[New LWP 288092]
[New LWP 288094]
[New LWP 288097]
[New LWP 288098]
[New LWP 288100]
[New LWP 288101]
[New LWP 288103]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Core was generated by `./hlds_linux -port 42069 -game svencoop +log on +map _server_start +as_log_leve'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0xe0415acb in ?? () from /[hidden]/anarchy_svends_526/svencoop/addons/metamod/dlls/metamod_i386.so
[Current thread is 1 (Thread 0xf7a31940 (LWP 288086))]
#0  0xe0415acb in ?? () from /[hidden]/anarchy_svends_526/svencoop/addons/metamod/dlls/metamod_i386.so
#1  0xe0415b8d in ?? () from /[hidden]/anarchy_svends_526/svencoop/addons/metamod/dlls/metamod_i386.so
#2  0xe0415c22 in meta_rebuild_callbacks() () from /[hidden]/anarchy_svends_526/svencoop/addons/metamod/dlls/metamod_i386.so
#3  0xe041712c in MPluginList::refresh(PLUG_LOADTIME) () from /[hidden]/anarchy_svends_526/svencoop/addons/metamod/dlls/metamod_i386.so
#4  0xe0412b4a in mm_ServerDeactivate() () from /[hidden]/anarchy_svends_526/svencoop/addons/metamod/dlls/metamod_i386.so
#5  0xf6056bf2 in Host_Changelevel_f() () from /[hidden]/anarchy_svends_526/engine_i486.so
#6  0xf607b205 in Cmd_ExecuteString_internal(char const*, cmd_source_s, IGameClient*) () from /[hidden]/anarchy_svends_526/engine_i486.so
#7  0xf607b4eb in Cmd_ExecuteString(char*, cmd_source_s) () from /[hidden]/anarchy_svends_526/engine_i486.so
#8  0xf607b64b in Cbuf_Execute() () from /[hidden]/anarchy_svends_526/engine_i486.so
#9  0xf6055740 in _Host_Frame(float) () from /[hidden]/anarchy_svends_526/engine_i486.so
#10 0xf6055a5d in Host_Frame(float, int, int*) () from /[hidden]/anarchy_svends_526/engine_i486.so
#11 0xf6051488 in CEngine::Frame() () from /[hidden]/anarchy_svends_526/engine_i486.so
#12 0xf6050750 in CDedicatedServerAPI::RunFrame() () from /[hidden]/anarchy_svends_526/engine_i486.so
#13 0x08049e6d in RunEngine() ()
#14 0x0804a07f in StartServer(char*) ()
#15 0x0804949f in main ()

What's funnier is that I'm running ReHLDS.