I can crash Julia 1.5 and 1.6 reliably with this code

[xiaodaigh]

This piece of code if run in the REPL can reliably crash Julia on both Windows and Linux (WSL2 Ubuntu 18.04) on both Julia v1.5 and v1.6

import Base.*
a::Int * b::Int = a + b

Error message

``` signal (11): Segmentation fault in expression starting at none:0 jl_f_tuple at /buildworker/worker/package_linux64/build/src/builtins.c:721 iterate at ./essentials.jl:601 [inlined] iterate at ./essentials.jl:601 _jl_invoke at /buildworker/worker/package_linux64/build/src/gf.c:2231 [inlined] jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:2398 to_tuple_type at ./reflection.jl:775 methods at ./reflection.jl:902 methods at ./reflection.jl:922 [inlined] methods at ./reflection.jl:922 _jl_invoke at /buildworker/worker/package_linux64/build/src/gf.c:2231 [inlined] jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:2398 show at ./show.jl:38 unknown function (ip: 0x7ff3e8a6e205) _jl_invoke at /buildworker/worker/package_linux64/build/src/gf.c:2231 [inlined] jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:2398 display at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.5/REPL/src/REPL.jl:214 display at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.5/REPL/src/REPL.jl:218 _jl_invoke at /buildworker/worker/package_linux64/build/src/gf.c:2231 [inlined] jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:2398 display at ./multimedia.jl:328 _jl_invoke at /buildworker/worker/package_linux64/build/src/gf.c:2214 [inlined] jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:2398 jl_apply at /buildworker/worker/package_linux64/build/src/julia.h:1690 [inlined] do_apply at /buildworker/worker/package_linux64/build/src/builtins.c:655 jl_f__apply_latest at /buildworker/worker/package_linux64/build/src/builtins.c:705 #invokelatest#1 at ./essentials.jl:710 [inlined] invokelatest at ./essentials.jl:709 [inlined] print_response at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.5/REPL/src/REPL.jl:238 print_response at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.5/REPL/src/REPL.jl:223 do_respond at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.5/REPL/src/REPL.jl:822 jfptr_do_respond_60634.clone_1 at /home/xiaodai/julia-1.5.0/lib/julia/sys.so (unknown line) _jl_invoke at /buildworker/worker/package_linux64/build/src/gf.c:2214 [inlined] jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:2398 jl_apply at /buildworker/worker/package_linux64/build/src/julia.h:1690 [inlined] do_apply at /buildworker/worker/package_linux64/build/src/builtins.c:655 jl_f__apply_latest at /buildworker/worker/package_linux64/build/src/builtins.c:705 #invokelatest#1 at ./essentials.jl:710 [inlined] invokelatest at ./essentials.jl:709 [inlined] run_interface at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.5/REPL/src/LineEdit.jl:2355 jfptr_run_interface_59827.clone_1 at /home/xiaodai/julia-1.5.0/lib/julia/sys.so (unknown line) _jl_invoke at /buildworker/worker/package_linux64/build/src/gf.c:2214 [inlined] jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:2398 run_frontend at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.5/REPL/src/REPL.jl:1143 #38 at ./task.jl:356 jfptr_YY.38_60720.clone_1 at /home/xiaodai/julia-1.5.0/lib/julia/sys.so (unknown line) _jl_invoke at /buildworker/worker/package_linux64/build/src/gf.c:2214 [inlined] jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:2398 jl_apply at /buildworker/worker/package_linux64/build/src/julia.h:1690 [inlined] start_task at /buildworker/worker/package_linux64/build/src/task.c:707 unknown function (ip: (nil)) Allocations: 3616394 (Pool: 3615009; Big: 1385); GC: 4 Segmentation fault ```

`versioninfo()`

Julia Version 1.5.1
Commit 697e782ab8 (2020-08-25 20:08 UTC)
Platform Info:
  OS: Windows (x86_64-w64-mingw32)
  CPU: Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-9.0.1 (ORCJIT, skylake)
Environment:
  JULIA_EDITOR = sublime_text
  JULIA_NUM_THREADS = 6
  JULIA_PKG_DEVDIR = c:/git/

[KristofferC]

Breaking methods used within Julia (type piracy) can indeed crash the system. This is expected.