Illegal instruction when calling DataFrames function

[nalimilan]

When running the following code using the nl/grouping2 branch of DataFrames (commit 256bd1d), Julia 0.7, 1.0 and master crashes with "Illegal instruction".

using Pkg
Pkg.add("DataFrames#nl/grouping2")
using DataFrames
df = DataFrame(Key1 = CategoricalArray(["A", "A", "B", "B"]),
               Key2 = CategoricalArray(["A", "B", "A", "B"]),
               Value = 1:4)
combine(d -> DataFrame(x=d[1, :Key2]), groupby(df, :Key1))

Unreachable reached at 0x7f4bc01192fd

signal (4): Illegal instruction
in expression starting at no file:0
append_rows! at /home/milan/.julia/dev/DataFrames/src/groupeddataframe/grouping.jl:357
_combine! at /home/milan/.julia/dev/DataFrames/src/groupeddataframe/grouping.jl:373
unknown function (ip: 0x7f4bc0118c75)
jl_fptr_trampoline at /home/milan/Dev/julia/src/gf.c:1843
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2198
_combine at /home/milan/.julia/dev/DataFrames/src/groupeddataframe/grouping.jl:261
jl_fptr_trampoline at /home/milan/Dev/julia/src/gf.c:1843
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2198
combine at /home/milan/.julia/dev/DataFrames/src/groupeddataframe/grouping.jl:238
jl_fptr_trampoline at /home/milan/Dev/julia/src/gf.c:1843
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2198
do_call at /home/milan/Dev/julia/src/interpreter.c:324
eval_value at /home/milan/Dev/julia/src/interpreter.c:430
eval_stmt_value at /home/milan/Dev/julia/src/interpreter.c:363 [inlined]
eval_body at /home/milan/Dev/julia/src/interpreter.c:678
jl_interpret_toplevel_thunk_callback at /home/milan/Dev/julia/src/interpreter.c:808
unknown function (ip: 0xfffffffffffffffe)
unknown function (ip: 0x7f4ba66bce1f)
unknown function (ip: 0x7)
jl_interpret_toplevel_thunk at /home/milan/Dev/julia/src/interpreter.c:817
jl_toplevel_eval_flex at /home/milan/Dev/julia/src/toplevel.c:818
jl_toplevel_eval_in at /home/milan/Dev/julia/src/builtins.c:622
eval at ./boot.jl:319
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2198
eval_user_input at /home/milan/Dev/julia/usr/share/julia/stdlib/v1.1/REPL/src/REPL.jl:85
macro expansion at /home/milan/Dev/julia/usr/share/julia/stdlib/v1.1/REPL/src/REPL.jl:117 [inlined]
#28 at ./task.jl:259
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2198
jl_apply at /home/milan/Dev/julia/src/julia.h:1559 [inlined]
start_task at /home/milan/Dev/julia/src/task.c:271
unknown function (ip: 0xffffffffffffffff)
Allocations: 39452559 (Pool: 39445133; Big: 7426); GC: 85
Illegal instruction (core dumped)

EDIT: looking at the assembly in gdb, the problematic instruction is ud2:

   │0x7fffd4163f03 <julia_append_rows!_-548180969+1251>     mov    %r15,0x48(%rbx)                                                             │
   │0x7fffd4163f07 <julia_append_rows!_-548180969+1255>     movabs $0x7ffff74da9ed,%rax                                                        │
   │0x7fffd4163f11 <julia_append_rows!_-548180969+1265>     lea    0x38(%rbx),%rdi                                                             │
   │0x7fffd4163f15 <julia_append_rows!_-548180969+1269>     mov    $0x3,%esi                                                                   │
   │0x7fffd4163f1a <julia_append_rows!_-548180969+1274>     callq  *%rax                                                                       │
  >│0x7fffd4163f1c <julia_append_rows!_-548180969+1276>     ud2                                                                                │
   │0x7fffd4163f1e <julia_append_rows!_-548180969+1278>     mov    %rsp,%rax                                                                   │
   │0x7fffd4163f21 <julia_append_rows!_-548180969+1281>     lea    -0x10(%rax),%rsi                                                            

[JeffBezanson]

Should check whether #29406 or #29380 fixes this.

[galenlynch]

I'm running into the same problem, and same illegal instruction, with some code that I wrote on Julia 1.0 (official binaries). It might be difficult to distil it into a reproducible example, but FWIW I can run each line of the function in the REPL without a problem, however calling the function causes julia to be terminated by SIGILL.

[galenlynch]

@code_warntype showed that I had a fair amount of type instability in the function that would reliably crash. Fixing the type stability fixed the SIGILL crashes.

[JeffBezanson]

#29406 seems to fix this for me.

[nalimilan]

#29406 fixes it! But as you note it also introduces new ambiguities. I'd rather fix these than keep the bug, but maybe not all package authors agree...

[nalimilan]

BTW, do you think we could work around it?

[JeffBezanson]

To attempt that, I'd look at code_typed for append_rows! where the crash is. The crash is probably at the first point with a wrong ::Union{} type annotation. If we didn't infer exact argument types there, adding type annotations might help. If that's not the problem, it may be necessary to weaken type information with e.g. Ref{Any}(x)[]. If performance is important here that will be a problem though.

[nalimilan]

Thanks. There's indeed a isa(x, Type{Union{}}} check, but also lots of weird DataFrames.eltype and DataFrames.promote_type, as if the method didn't come from Base. Unfortunately I don't know the type (that's the point of using promotion), so I cannot really add better annotations. In case you want to have a look: https://gist.github.com/nalimilan/0021fb27e64f1d682206610824f7f0bf

[nalimilan]

FWIW I've eventually found out that moving the append! call to a separate function which also takes a Boolean indicating whether it should actually call it or not works around the bug (JuliaData/DataFrames.jl@4e7f044).