Fix usage of assure

[jankoboehm]

This removes the wrong usage of assure in the standard basis command for ideals. Possibly the last occurance. According to local tests, it should result in a segfault arising from the test "MPolyAnyMap/MPolyQuoRing segfault", which can be run by

  Oscar.test_module("Rings/MPolyAnyMap/MPolyQuo")

Note that the segfault only appears over

  Qi, i = quadratic_field(-1)

but not over QQ.

Once this is through, close #2109, since it is completely covered.

[fingolfin]

So I guess now we need @hannes14 to help determine why it crashes?

[fingolfin]

Just to say, the crash I get is

Test Summary:                        |Time
MPolyAnyMap/MPolyQuoRing no segfault | None  9.4s

[41341] signal (11.2): Segmentation fault: 11
in expression starting at /Users/mhorn/Projekte/OSCAR/Oscar.spielwiese/test/Rings/MPolyAnyMap/MPolyQuo.jl:10
_Z21maMap_CreatePolyIdealP10sip_sidealP8ip_sringS2_S2_RP8mapoly_sRP9maideal_s at /Users/mhorn/.julia/artifacts/b370e340135e825b6ea825fc19f912214fc6df9a/lib/libSingular-4.3.2.dylib (unknown line)
Allocations: 50365024 (Pool: 50307809; Big: 57215); GC: 34
ERROR: failed process: Process(`/Users/mhorn/.julia/juliaup/julia-1.9.3+0.aarch64.apple.darwin14/bin/julia -Cnative -J/Users/mhorn/.julia/juliaup/julia-1.9.3+0.aarch64.apple.darwin14/lib/julia/sys.dylib -g1 --project=/Users/mhorn/Projekte/OSCAR/Oscar.spielwiese/p/1.9/Project.toml -e 'using Test; using Oscar; Hecke.assertions(true); include("/Users/mhorn/Projekte/OSCAR/Oscar.spielwiese/test/Rings/MPolyAnyMap/MPolyQuo.jl");'`, ProcessSignaled(11)) [0]

Stacktrace:
 [1] pipeline_error
   @ ./process.jl:565 [inlined]
 [2] run(::Cmd; wait::Bool)
   @ Base ./process.jl:480
 [3] run
   @ ./process.jl:477 [inlined]
 [4] test_module(file::String; new::Bool)
   @ Oscar ~/Projekte/OSCAR/Oscar.spielwiese/src/utils/tests.jl:21
 [5] test_module(file::String)
   @ Oscar ~/Projekte/OSCAR/Oscar.spielwiese/src/utils/tests.jl:12
 [6] top-level scope
   @ REPL[3]:1

The C++ symbol demangles to maMap_CreatePolyIdeal(sip_sideal*, ip_sring*, ip_sring*, ip_sring*, mapoly_s*&, maideal_s*&).

I guess it would be useful to have a more complete backtrace... So here is an interactive session:

julia> Qi, i = quadratic_field(-1)
(Imaginary quadratic field defined by x^2 + 1, sqrt(-1))

julia> Qix, (x, y) = Qi["x", "y"]
(Multivariate polynomial ring in 2 variables over imaginary quadratic field defined by x^2 + 1, AbstractAlgebra.Generic.MPoly{nf_elem}[x, y])

julia> I = ideal(Qix, elem_type(Qix)[])
ideal()

julia> Qix, = quo(Qix, I)
(Quotient of multivariate polynomial ring by ideal with 0 generators, Map from
Multivariate polynomial ring in 2 variables over imaginary quadratic field defined by x^2 + 1 to Qix defined by a julia-function with inverse)

julia> x = Qix(x)
x

julia> y = Qix(y)
y

julia> f = hom(Qix, Qix, [x^2, y^2])

Process 40778 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
    frame #0: 0x00000002bba215f4 libSingular-4.3.2.dylib`maMap_CreatePolyIdeal(sip_sideal*, ip_sring*, ip_sring*, ip_sring*, mapoly_s*&, maideal_s*&) + 148
libSingular-4.3.2.dylib`maMap_CreatePolyIdeal:
->  0x2bba215f4 <+148>: ldr    x8, [x26]
    0x2bba215f8 <+152>: ldr    x25, [x8, #0x8]
    0x2bba215fc <+156>: cbz    x25, 0x2bba21978          ; <+1048>
    0x2bba21600 <+160>: ldr    x9, [x8]
Target 0: (julia) stopped.
(lldb) bt
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
  * frame #0: 0x00000002bba215f4 libSingular-4.3.2.dylib`maMap_CreatePolyIdeal(sip_sideal*, ip_sring*, ip_sring*, ip_sring*, mapoly_s*&, maideal_s*&) + 148
    frame #1: 0x00000002bba2239c libSingular-4.3.2.dylib`fast_map_common_subexp(sip_sideal*, ip_sring*, sip_sideal*, ip_sring*) + 124
    frame #2: 0x00000002bbc14444 libsingular_julia.dylib`std::__1::__function::__func<singular_define_ideals(jlcxx::Module&)::$_33, std::__1::allocator<singular_define_ideals(jlcxx::Module&)::$_33>, sip_sideal* (sip_sideal*, ip_sring*, sip_sideal*, ip_sring*, void*)>::operator()(sip_sideal*&&, ip_sring*&&, sip_sideal*&&, ip_sring*&&, void*&&) + 84
    frame #3: 0x00000002bbc14314 libsingular_julia.dylib`jlcxx::detail::CallFunctor<sip_sideal*, sip_sideal*, ip_sring*, sip_sideal*, ip_sring*, void*>::apply(void const*, jlcxx::WrappedCppPtr, jlcxx::WrappedCppPtr, jlcxx::WrappedCppPtr, jlcxx::WrappedCppPtr, void*) + 68
    frame #4: 0x00000002d7ee40c8
    frame #5: 0x00000002d26e424c
    frame #6: 0x00000002b9c140e0
    frame #7: 0x00000001016264ec libjulia-internal.1.9.dylib`do_call + 188
    frame #8: 0x0000000101624d10 libjulia-internal.1.9.dylib`eval_body + 1476
    frame #9: 0x000000010162535c libjulia-internal.1.9.dylib`jl_interpret_toplevel_thunk + 260
    frame #10: 0x000000010163c59c libjulia-internal.1.9.dylib`jl_toplevel_eval_flex + 4620
    frame #11: 0x000000010163c4c0 libjulia-internal.1.9.dylib`jl_toplevel_eval_flex + 4400
    frame #12: 0x000000010163d2e4 libjulia-internal.1.9.dylib`ijl_toplevel_eval_in + 156
    frame #13: 0x0000000118b8d070 sys.dylib`japi1_eval_user_input_60004 at boot.jl:370
    frame #14: 0x0000000118b8da30 sys.dylib`julia_repl_backend_loop_61406 at REPL.jl:249
    frame #15: 0x0000000118b8e46c sys.dylib`japi1_YY.start_repl_backendYY.46_60048 at REPL.jl:234
    frame #16: 0x0000000118b8e648 sys.dylib`japi1_start_repl_backend_25046 at REPL.jl:231
    frame #17: 0x000000010160d5c4 libjulia-internal.1.9.dylib`ijl_apply_generic + 1732
...

[fingolfin]

@hannes14 running with a Singular & libsingular-julia compiled with -g, and Singular with --enable-debug, I am getting:

julia> f = hom(Qix, Qix, [x^2, y^2])
***omError_NullSizeAlloc: alloc of size 0
 occurred at:
  #0 at ??:0                 in ??
Ring homomorphism
  from quotient of multivariate polynomial ring by ideal()
  to quotient of multivariate polynomial ring by ideal()
defined by
  x -> x^2
  y -> y^2

I set a breakpoint on omReportError and got this backtrace:

* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.2
  * frame #0: 0x000000016ff3807c libomalloc-0.9.6.dylib`omReportError(error=omError_NullSizeAlloc, report_error=omError_NoError, r=0x00000002c9437c50, fmt="") at omError.c:85:7
    frame #1: 0x000000016ff30634 libomalloc-0.9.6.dylib`_omDebugAlloc(size_bin=0x0000000000000000, flags=34, check='\x01', track='\x04') at omDebug.c:133:7
    frame #2: 0x00000002c9437c50 libSingular-4.3.2.dylib`maMap_CreatePolyIdeal(map_id=0x00000002c7c4bd88, map_r=0x00000002c7c3e3d8, src_r=0x00000002c7c3e510, dest_r=0x00000002c7c3e8b8, mp=0x000000016d206668, mideal=0x000000016d206660) at fast_maps.cc:260:35
    frame #3: 0x00000002c94383e0 libSingular-4.3.2.dylib`fast_map_common_subexp(map_id=0x00000002c7c4bd88, map_r=0x00000002c7c3e3d8, image_id=0x00000002c7c4e138, image_r=0x00000002c7c3e3d8) at fast_maps.cc:377:3
    frame #4: 0x00000002c943b33c libSingular-4.3.2.dylib`maMapIdeal(map_id=0x00000002c7c4bd88, preimage_r=0x00000002c7c3e3d8, image_id=0x00000002c7c4e138, image_r=0x00000002c7c3e3d8, nMap=(libpolys-4.3.2.dylib`ndCopyMap(snumber*, n_Procs_s*, n_Procs_s*) at numbers.cc:292))(snumber*, n_Procs_s*, n_Procs_s*)) at gen_maps.cc:132:16
    frame #5: 0x00000002c207eaec libsingular_julia.dylib`std::__1::__function::__func<singular_define_ideals(jlcxx::Module&)::$_33, std::__1::allocator<singular_define_ideals(jlcxx::Module&)::$_33>, sip_sideal* (sip_sideal*, ip_sring*, sip_sideal*, ip_sring*, void*)>::operator()(sip_sideal*&&, ip_sring*&&, sip_sideal*&&, ip_sring*&&, void*&&) + 84
    frame #6: 0x00000002c207ea00 libsingular_julia.dylib`jlcxx::detail::CallFunctor<sip_sideal*, sip_sideal*, ip_sring*, sip_sideal*, ip_sring*, void*>::apply(void const*, jlcxx::WrappedCppPtr, jlcxx::WrappedCppPtr, jlcxx::WrappedCppPtr, jlcxx::WrappedCppPtr, void*) + 68
...

[fingolfin]

(This is with Singular 4.3.2p12, commit Singular/Singular@3bda0f8)

[fingolfin]

So yeah, we are taking an ideal with zero generators, and that code in the Singular kernel doesn't seem to deal well with it...

[fingolfin]

@hannes14 implemented a fix in Singular, we'll retest once that has landed in a Singular.jl release

[fingolfin]

Seems to be working now