eval and execute at toplevel is (still) invalid

[jakobnissen]

This problem happens on Julia 1.6.7, 1.7.3, 1.8.5, 1.9.3, 1.10-beta2 and master. It might possibly also happens on older versions, but Automa.jl only supports Julia 1.6 and above.
MWE:

Reduced to this snippet with the help of @maleadt

struct Tokenizer end
define_iterate() = :(Base.iterate(::Tokenizer) = nothing)

for x in 1
    eval(define_iterate())
    iterate(Tokenizer())
end

Old way of of reproducing
Make a test file /tmp/foo.jl with the following content

using Automa
for goto in (false,)
    make_tokenizer([re"ADF"]; goto=false) |> eval
    collect(Tokenizer{UInt32, String, 1}("")) == []
end

Now, in a project with Automa master branch, #733b8cf (or the released v1.0.0)

julia> using Automa
julia> include("/tmp/foo.jl") # crashes

Interestingly, if, instead of generating the code during the session, we instead manually write out the code like this, it does not crash:

julia> open("/tmp/foo3.jl", "w") do io
           println(io, "using Automa")
           println(io, "for goto in (false,)")
           println(io, make_tokenizer([re"ADF"]; goto=false))
           println(io, "collect(Tokenizer{UInt32, String, 1}(\"\")) == []")
           println(io, "end")
       end

Also, including the file after manually running make_tokenizer doesn't crash either:

julia> using Automa

julia> make_tokenizer([re"ADF"]; goto=false) |> eval

julia> include("/tmp/foo.jl")

...which suggests to me that the bug could have something to do with the Julia interpreter, which runs the top-level for loop in foo.jl

Crash message:

Unreachable reached at 0x7f4628f24b7a

[54249] signal (4.2): Illegal instruction
in expression starting at /tmp/foo.jl:3
_collect at ./array.jl:768
collect at ./array.jl:757
top-level scope at /tmp/foo.jl:7
jl_toplevel_eval_flex at /home/jakni/code/julia/src/toplevel.c:925
jl_toplevel_eval_flex at /home/jakni/code/julia/src/toplevel.c:877
ijl_toplevel_eval_in at /home/jakni/code/julia/src/toplevel.c:985
eval at ./boot.jl:396 [inlined]
include_string at ./loading.jl:2070
_include at ./loading.jl:2130
include at ./client.jl:489
unknown function (ip: 0x7f4628f248e5)
jl_apply at /home/jakni/code/julia/src/julia.h:1993 [inlined]
do_call at /home/jakni/code/julia/src/interpreter.c:125
eval_value at /home/jakni/code/julia/src/interpreter.c:222
eval_stmt_value at /home/jakni/code/julia/src/interpreter.c:173 [inlined]
eval_body at /home/jakni/code/julia/src/interpreter.c:634
jl_interpret_toplevel_thunk at /home/jakni/code/julia/src/interpreter.c:774
jl_toplevel_eval_flex at /home/jakni/code/julia/src/toplevel.c:934
jl_toplevel_eval_flex at /home/jakni/code/julia/src/toplevel.c:877
ijl_toplevel_eval_in at /home/jakni/code/julia/src/toplevel.c:985
eval at ./boot.jl:396 [inlined]
eval_user_input at /home/jakni/code/julia/usr/share/julia/stdlib/v1.11/REPL/src/REPL.jl:150
repl_backend_loop at /home/jakni/code/julia/usr/share/julia/stdlib/v1.11/REPL/src/REPL.jl:246
#start_repl_backend#46 at /home/jakni/code/julia/usr/share/julia/stdlib/v1.11/REPL/src/REPL.jl:231
start_repl_backend at /home/jakni/code/julia/usr/share/julia/stdlib/v1.11/REPL/src/REPL.jl:228
#run_repl#59 at /home/jakni/code/julia/usr/share/julia/stdlib/v1.11/REPL/src/REPL.jl:387
run_repl at /home/jakni/code/julia/usr/share/julia/stdlib/v1.11/REPL/src/REPL.jl:373
jfptr_run_repl_92277 at /home/jakni/code/julia/usr/lib/julia/sys.so (unknown line)
#1043 at ./client.jl:432
jfptr_YY.1043_83306 at /home/jakni/code/julia/usr/lib/julia/sys.so (unknown line)
jl_apply at /home/jakni/code/julia/src/julia.h:1993 [inlined]
jl_f__call_latest at /home/jakni/code/julia/src/builtins.c:812
#invokelatest#2 at ./essentials.jl:899 [inlined]
invokelatest at ./essentials.jl:896 [inlined]
run_main_repl at ./client.jl:415
exec_options at ./client.jl:332
_start at ./client.jl:552
jfptr__start_83334 at /home/jakni/code/julia/usr/lib/julia/sys.so (unknown line)
jl_apply at /home/jakni/code/julia/src/julia.h:1993 [inlined]
true_main at /home/jakni/code/julia/src/jlapi.c:582
jl_repl_entrypoint at /home/jakni/code/julia/src/jlapi.c:731
main at /home/jakni/code/julia/cli/loader_exe.c:58
unknown function (ip: 0x7f462a227ccf)
__libc_start_main at /usr/lib/libc.so.6 (unknown line)
_start at /home/jakni/code/julia/julia (unknown line)
Allocations: 4208949 (Pool: 4205166; Big: 3783); GC: 6
zsh: illegal hardware instruction (core dumped)  ~/code/julia/julia --project=. --startup-file=no

[maleadt]

Reduced:

struct Tokenizer
end
Base.IteratorSize(::Type{Tokenizer}) = Base.SizeUnknown()
function make_tokenizer()
    quote
        Base.iterate(::Tokenizer, state=0) = nothing
    end
end
for x in 1
    eval(make_tokenizer())
    collect(Tokenizer())
end

Reproduces all the way back to 1.0.

[vtjnash]

No, that is just the well-known issue that you are not permitted to both eval and execute code in a loop at top-level

[brenhinkeller]

No, that is just the well-known issue that you are not permitted to both eval and execute code in a loop at top-level

Seems not so well-known.. what is the cause/rationale?

[jakobnissen]

I've been watching the issue tracker for like two years and wrttiten Julia code daily for five years, so it can't be that well known.
If this is not technically fixable, could eval detect that it was being run in a top-level loop and throw an exception?

[maleadt]

could eval detect that it was being run in a top-level loop and throw an exception?

Running eval in a top-level loop is a very common pattern, e.g., https://github.com/JuliaLang/julia/blob/87e31a5d5e054dd2e48fab0c8ce4f7e8f7facce7/base/arraymath.jl#L5C1-L10. The problem seems to be with the subsequent collect which relies on functionality evaled right before (a limitation I wasn't aware of either).

[jakobnissen]

It's not the collect - see the reduced MWE at the top of OP which is your example, but a bit further reduced

[maleadt]

It's not the collect - see the reduced MWE at the top of OP which is your example, but a bit further reduced

Well, it is the iterate that gets triggered by the collect. I just meant that it's the code executed after the eval

[mbauman]

I think I would normally expect a world age error here, no?

[vtjnash]

Correct. But codegen intentionally skips emitting that error, which can sometimes lead to crashes like this