[CameraServer] destroy VideoListener first

[mcm001]

[potentially] fixes #7685

[PeterJohnson]

Have you been able to confirm that this fixes the issue?

[mcm001]

I haven't yet. @Sam948-byte had that in work

[Sam948-byte]

I haven't yet. @Sam948-byte had that in work

I wasn't able to get to that last night. I think the earliest I can test is probably tomorrow night.

[auscompgeek]

A test that reproduces the issue with ASan + TSan would be good.

[mcm001]

I'm not sure what Photon does that wpilib's ci doesn't that would trigger this bug in the first place. Allwpilib already has tests run under sanitizers.

[auscompgeek]

I don't see any tests for CameraServer 😅

[mcm001]

i suppose that would do it, eh? lol. we should upstream some tests, then

[mcm001]

I'm sometimes seeing new one this locally, and even with this patch, I'm still seeing use-after-frees. Could we be removing the listener after the callback has been invoked by the callback thread? I don't see any synchronization happen in CallbackManager::Remove at all.

AddressSanitizer:DEADLYSIGNAL
=================================================================
==62371==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x7f9117f8f382 bp 0x7ffe9a902b20 sp 0x7ffe9a902b10 T0)
==62371==The signal is caused by a READ memory access.
==62371==Hint: address points to the zero page.
    #0 0x7f9117f8f382 in wpi::DenseMapInfo<unsigned int, void>::isEqual(unsigned int const&, unsigned int const&) /home/matt/allwpilib/wpiutil/src/main/native/thirdparty/llvm/include/wpi/DenseMapInfo.h:132
    #1 0x7f9116df16c5 in destroyAll /home/matt/allwpilib/wpiutil/src/main/native/thirdparty/llvm/include/wpi/DenseMap.h:410
    #2 0x7f9116df0ceb in ~DenseMap /home/matt/allwpilib/wpiutil/src/main/native/thirdparty/llvm/include/wpi/DenseMap.h:798
    #3 0x7f9116decc5f in ~HandleManager /home/matt/allwpilib/wpiutil/src/main/native/cpp/Synchronization.cpp:31
    #4 0x7f911449ba75 in __run_exit_handlers stdlib/exit.c:108
    #5 0x7f911449bbbd in __GI_exit stdlib/exit.c:138
    #6 0x7f911447e1d0 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:74
    #7 0x7f911447e28a in __libc_start_main_impl ../csu/libc-start.c:360
    #8 0x55e5e762c5a4 in _start (/home/matt/allwpilib/build-cmake/bin/cameraserver_test+0x55a4) (BuildId: 3cdebe83132b3982899c6c909a559e91072cdd8e)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /home/matt/allwpilib/wpiutil/src/main/native/thirdparty/llvm/include/wpi/DenseMapInfo.h:132 in wpi::DenseMapInfo<unsigned int, void>::isEqual(unsigned int const&, unsigned int const&)
==62371==ABORTING