$ RUSTFLAGS="-Z sanitizer=thread" cargo run --target x86_64-apple-darwin
   Compiling nodrop v0.1.12
   Compiling stable_deref_trait v1.1.0
   Compiling servo_arc v0.1.1 (file:///Users/vadzim/Downloads/relay/servo_arc)
   Compiling relay v0.1.0 (file:///Users/vadzim/Downloads/relay)
    Finished dev [unoptimized + debuginfo] target(s) in 1.38s
     Running `target/x86_64-apple-darwin/debug/relay`
==================
WARNING: ThreadSanitizer: data race (pid=19187)
  Write of size 4 at 0x7b0400000058 by thread T2:
    #0 relay::main::_$u7b$$u7b$closure$u7d$$u7d$::h76093e6e5cffb50f main.rs:23 (relay:x86_64+0x10000a33b)
    #1 std::sys_common::backtrace::__rust_begin_short_backtrace::h827422d22fa26fec backtrace.rs:136 (relay:x86_64+0x10000a787)
    #2 std::thread::Builder::spawn::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h50b6d22ab7a3efde mod.rs:409 (relay:x86_64+0x100003767)
    #3 _$LT$std..panic..AssertUnwindSafe$LT$F$GT$$u20$as$u20$core..ops..function..FnOnce$LT$$LP$$RP$$GT$$GT$::call_once::h1fa2c78f45152800 panic.rs:313 (relay:x86_64+0x1000085c7)
    #4 std::panicking::try::do_call::heb268bb7d689922a panicking.rs:310 (relay:x86_64+0x1000063ed)
    #5 __rust_maybe_catch_panic lib.rs:106 (relay:x86_64+0x10002592e)
    #6 std::panic::catch_unwind::hc1196e4c87b17552 panic.rs:392 (relay:x86_64+0x100008787)
    #7 std::thread::Builder::spawn::_$u7b$$u7b$closure$u7d$$u7d$::he7289438d1fd68ed mod.rs:408 (relay:x86_64+0x10000352b)
    #8 _$LT$F$u20$as$u20$alloc..boxed..FnBox$LT$A$GT$$GT$::call_box::ha184d6c6da072dc3 boxed.rs:640 (relay:x86_64+0x100003aa4)
    #9 std::sys::unix::thread::Thread::new::thread_start::h4d5ebaa4df00ca02 thread.rs:24 (relay:x86_64+0x10000c99b)

  Previous read of size 4 at 0x7b0400000058 by thread T1:
    #0 relay::main::_$u7b$$u7b$closure$u7d$$u7d$::h0496aa757202d1e5 main.rs:12 (relay:x86_64+0x10000a1e6)
    #1 std::sys_common::backtrace::__rust_begin_short_backtrace::hea1597b53e549b68 backtrace.rs:136 (relay:x86_64+0x10000a817)
    #2 std::thread::Builder::spawn::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h87adee2b497b886e mod.rs:409 (relay:x86_64+0x1000037f7)
    #3 _$LT$std..panic..AssertUnwindSafe$LT$F$GT$$u20$as$u20$core..ops..function..FnOnce$LT$$LP$$RP$$GT$$GT$::call_once::ha9c3b3d29bed764f panic.rs:313 (relay:x86_64+0x100008657)
    #4 std::panicking::try::do_call::h9aeb8552a2881cfb panicking.rs:310 (relay:x86_64+0x10000631d)
    #5 __rust_maybe_catch_panic lib.rs:106 (relay:x86_64+0x10002592e)
    #6 std::panic::catch_unwind::h9b81092b9270292f panic.rs:392 (relay:x86_64+0x1000086e7)
    #7 std::thread::Builder::spawn::_$u7b$$u7b$closure$u7d$$u7d$::h607f2a80036d8eb7 mod.rs:408 (relay:x86_64+0x1000031fb)
    #8 _$LT$F$u20$as$u20$alloc..boxed..FnBox$LT$A$GT$$GT$::call_box::h38cbde99a50afeb6 boxed.rs:640 (relay:x86_64+0x1000039e4)
    #9 std::sys::unix::thread::Thread::new::thread_start::h4d5ebaa4df00ca02 thread.rs:24 (relay:x86_64+0x10000c99b)

  Location is heap block of size 16 at 0x7b0400000050 allocated by main thread:
    #0 malloc <null>:4744960 (libclang_rt.tsan_osx_dynamic.dylib:x86_64+0x2b07a)
    #1 alloc::alloc::alloc::hbba0b03a9bfa997c alloc.rs:62 (relay:x86_64+0x100001e5a)
    #2 alloc::alloc::exchange_malloc::hc1d6900decd739ca alloc.rs:157 (relay:x86_64+0x100001d83)
    #3 _$LT$alloc..boxed..Box$LT$T$GT$$GT$::new::ha003936d64c769f7 boxed.rs:96 (relay:x86_64+0x10000598b)
    #4 _$LT$servo_arc..Arc$LT$T$GT$$GT$::new::h9e11bfdd9cc87ca5 lib.rs:187 (relay:x86_64+0x10000566c)
    #5 relay::main::h6bfe6541f4e70b6b main.rs:7 (relay:x86_64+0x1000010ea)
    #6 std::rt::lang_start::_$u7b$$u7b$closure$u7d$$u7d$::ha30b5ebedebc1bb4 rt.rs:74 (relay:x86_64+0x1000074f5)
    #7 std::panicking::try::do_call::hc28f566d36dc1cc5 panicking.rs:310 (relay:x86_64+0x100019397)
    #8 main <null>:4744960 (relay:x86_64+0x1000013d0)

  Thread T2 (tid=1035748, running) created by main thread at:
    #0 pthread_create <null>:4745008 (libclang_rt.tsan_osx_dynamic.dylib:x86_64+0x890d)
    #1 std::sys::unix::thread::Thread::new::hb5434aec894b0ac7 thread.rs:78 (relay:x86_64+0x10000c66c)
    #2 std::thread::spawn::hedf4ccb750dcccb7 mod.rs:539 (relay:x86_64+0x100002238)
    #3 relay::main::h6bfe6541f4e70b6b main.rs:17 (relay:x86_64+0x10000120b)
    #4 std::rt::lang_start::_$u7b$$u7b$closure$u7d$$u7d$::ha30b5ebedebc1bb4 rt.rs:74 (relay:x86_64+0x1000074f5)
    #5 std::panicking::try::do_call::hc28f566d36dc1cc5 panicking.rs:310 (relay:x86_64+0x100019397)
    #6 main <null>:4745008 (relay:x86_64+0x1000013d0)

  Thread T1 (tid=1035747, finished) created by main thread at:
    #0 pthread_create <null>:4745008 (libclang_rt.tsan_osx_dynamic.dylib:x86_64+0x890d)
    #1 std::sys::unix::thread::Thread::new::hb5434aec894b0ac7 thread.rs:78 (relay:x86_64+0x10000c66c)
    #2 std::thread::spawn::hc88374a2613e35a8 mod.rs:539 (relay:x86_64+0x1000020f8)
    #3 relay::main::h6bfe6541f4e70b6b main.rs:9 (relay:x86_64+0x1000011d3)
    #4 std::rt::lang_start::_$u7b$$u7b$closure$u7d$$u7d$::ha30b5ebedebc1bb4 rt.rs:74 (relay:x86_64+0x1000074f5)
    #5 std::panicking::try::do_call::hc28f566d36dc1cc5 panicking.rs:310 (relay:x86_64+0x100019397)
    #6 main <null>:4745008 (relay:x86_64+0x1000013d0)

SUMMARY: ThreadSanitizer: data race main.rs:23 in relay::main::_$u7b$$u7b$closure$u7d$$u7d$::h76093e6e5cffb50f
==================
ThreadSanitizer: reported 1 warnings
Abort trap: 6