Bug hunting suggestions?

I’ve been using Fedora for a couple years and have had zero problems. Even Steam games have been working flawless this whole time.

I then stumbled into a situation that has left me stumped. I bought a Toliss aircraft for my X-Plane 12. Whenever the Toliss needs to connect to the internet to download flight plans. It locks up X-Plane 12. The X-Plane log files freeze at this moment so I have no data from this.

GDB did tell me:

Thread 1 “Main Thread” received signal SIGSEGV, Segmentation fault.
0x00007f9f4cd76385 in __GI___libc_free (mem=0x1) at malloc.c:3368
Downloading source file /usr/src/debug/glibc-2.38-16.fc39.x86_64/malloc/malloc.c
3368 if (chunk_is_mmapped (p)) /* release mmapped memory. */
(gdb)
Continuing.

I have disabled plugins, turned off firewalls (soft and router), looked into my resolve and NetworkManager settings to no avail.

Disabling ipv4 does prevent X-Plane from freezing and crashing, but the flight data transfer does not occur. It connects to Simbrief.com, which is ipv4 only.

I did ask Toliss for help, but they said their plane is working perfectly. :frowning:

I did some fresh install distro testing:

Toliss/X-Plane 12 works on Ubuntu 22.04 LTS, SUSE Leap 15.5, and oddly, Arch.
The pair does not work on Ubuntu 23.20, SUSE Tumbleweed, nor Fedora Worsations 39 and 40 Beta.

XP 11 does work fully with the Toliss aircraft, on every distro. :confused:

I’m not sure if Toliss uses curl to communicate with the Simbrief server.

The working of the rolling release of Arch has thrown me for a loop since I had been assuming that an upgrade to a unknown stable package had disrupted the functionality of Toliss/X-Plane 12.

X-Plane 11 works everywhere. X-Plane 12 mostly works on long term releases, and oddly Arch.

X-Plane only officially supports Ubuntu LTS, so they have no suggestions for me in regard to Fedora.

Any suggestions on where to look next for clues to solving this mystery?

Thank you.

Perhaps some buffer overflow somewhere. It could be something in the data you are trying to download which caused it. Or it could be something else, including program bug.

When you get a “Segmentation fault” the real error could have happened in a completely part of the program, and this makes diagnosing the cause very hard.

Not an uncommon response.

If something works in one Fedora Linux release but not the next, the Fedora Linux changesets are good place to check.

For Fedora Linux 39: Releases/39/ChangeSet - Fedora Project Wiki

One of the Fedora Linux 39 changes mentions mmap: Changes/IncreaseVmMaxMapCount - Fedora Project Wiki

Does temporarily reverting that value to its previous default work around the problem?

$ sudo sysctl -w vm.max_map_count=65530