unsafe_store! in Ptr{Void} asserts

[Keno]

We should either give a proper error for this or make it silently work:

julia> unsafe_store!(Ptr{Nothing}(C_NULL), nothing)
julia: /home/keno/julia-1.0/deps/srccache/llvm-6.0.1/lib/IR/Type.cpp:619: static llvm::PointerType* llvm::PointerType::get(llvm::Type*, unsigned int): Assertion `isValidElementType(EltTy) && "Invalid type for pointer element!"' failed.

signal (6): Aborted
in expression starting at no file:0
__libc_signal_restore_set at /build/glibc-itYbWN/glibc-2.26/signal/../sysdeps/unix/sysv/linux/nptl-signals.h:80 [inlined]
raise at /build/glibc-itYbWN/glibc-2.26/signal/../sysdeps/unix/sysv/linux/raise.c:48
abort at /build/glibc-itYbWN/glibc-2.26/stdlib/abort.c:90
__assert_fail_base at /build/glibc-itYbWN/glibc-2.26/assert/assert.c:92
__assert_fail at /build/glibc-itYbWN/glibc-2.26/assert/assert.c:101
_ZN4llvm11PointerType3getEPNS_4TypeEj at /home/keno/julia-1.0/usr/bin/../lib/libLLVM-6.0.so (unknown line)
emit_pointerset at /home/keno/julia-1.0/src/intrinsics.cpp:666 [inlined]
emit_intrinsic at /home/keno/julia-1.0/src/intrinsics.cpp:882
emit_call at /home/keno/julia-1.0/src/codegen.cpp:3136
emit_expr at /home/keno/julia-1.0/src/codegen.cpp:3908
emit_ssaval_assign at /home/keno/julia-1.0/src/codegen.cpp:3613
emit_stmtpos at /home/keno/julia-1.0/src/codegen.cpp:3805 [inlined]
emit_function at /home/keno/julia-1.0/src/codegen.cpp:6235
jl_compile_linfo at /home/keno/julia-1.0/src/codegen.cpp:1144
jl_fptr_trampoline at /home/keno/julia-1.0/src/gf.c:1819
jl_apply_generic at /home/keno/julia-1.0/src/gf.c:2209
do_call at /home/keno/julia-1.0/src/interpreter.c:323
eval_value at /home/keno/julia-1.0/src/interpreter.c:411
eval_stmt_value at /home/keno/julia-1.0/src/interpreter.c:362 [inlined]
eval_body at /home/keno/julia-1.0/src/interpreter.c:771
jl_interpret_toplevel_thunk_callback at /home/keno/julia-1.0/src/interpreter.c:883
unknown function (ip: 0xfffffffffffffffe)
unknown function (ip: 0x7f1a5151725f)
unknown function (ip: 0x1)
jl_interpret_toplevel_thunk at /home/keno/julia-1.0/src/interpreter.c:892
jl_toplevel_eval_flex at /home/keno/julia-1.0/src/toplevel.c:764
jl_toplevel_eval_in at /home/keno/julia-1.0/src/toplevel.c:793
eval at ./boot.jl:319
jl_apply_generic at /home/keno/julia-1.0/src/gf.c:2209
eval_user_input at /home/keno/julia-1.0/usr/share/julia/stdlib/v1.1/REPL/src/REPL.jl:85
macro expansion at /home/keno/julia-1.0/usr/share/julia/stdlib/v1.1/REPL/src/REPL.jl:117 [inlined]
#26 at ./task.jl:259
jl_apply_generic at /home/keno/julia-1.0/src/gf.c:2209
jl_apply at /home/keno/julia-1.0/src/julia.h:1571 [inlined]
start_task at /home/keno/julia-1.0/src/task.c:572
unknown function (ip: 0xffffffffffffffff)
Allocations: 2348689 (Pool: 2348226; Big: 463); GC: 4
Aborted

[Keno]

This comes up when trying to @threadcall a function that returns Cvoid.

[JeffBezanson]

Fixed by #31431.