Assertion error on CPLEX callbacks

[matbesancon]

I got the error on two distinct Debian machines. I am on CPLEX 12.08, which may cause the error?

ERROR: LoadError: TypeError: in typeassert, expected Tuple{CPLEX.Model,Function}, got a value of type Core.Compiler.UseRef
Stacktrace:
 [1] callback_wrapper(::Ptr{Nothing}, ::Int64, ::Ptr{Nothing}) at /home/mbesanco/.julia/packages/CPLEX/Hxpuk/src/cpx_generic_callbacks.jl:15
 [2] optimize! at /home/mbesanco/.julia/packages/CPLEX/Hxpuk/src/cpx_solve.jl:7 [inlined]
 [3] optimize!(::CPLEX.Optimizer) at /home/mbesanco/.julia/packages/CPLEX/Hxpuk/src/MOI/MOI_wrapper.jl:1897
 [4] optimize!(::MathOptInterface.Bridges.LazyBridgeOptimizer{CPLEX.Optimizer}) at /home/mbesanco/.julia/packages/MathOptInterface/bygN7/src/Bridges/bridge_optimizer.jl:239
 [5] optimize!(::MathOptInterface.Utilities.CachingOptimizer{MathOptInterface.AbstractOptimizer,MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Utilities.Model{Float64}}}) at /home/mbesanco/.julia/packages/MathOptInterface/bygN7/src/Utilities/cachingoptimizer.jl:189
 [6] optimize!(::Model, ::Nothing; bridge_constraints::Bool, ignore_optimize_hook::Bool, kwargs::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}) at /home/mbesanco/.julia/packages/JuMP/YXK4e/src/optimizer_interface.jl:131
 [7] optimize! at /home/mbesanco/.julia/packages/JuMP/YXK4e/src/optimizer_interface.jl:107 [inlined] (repeats 2 times)

I haven't managed to get a MWE yet, but the bug appears to be on code that was running before.
The breaking part is in cpx_generic_callback.jl:

function callback_wrapper(
    context::Ptr{Cvoid}, context_id::Clong, user_handle::Ptr{Cvoid}
)
    (model, callback_func) = unsafe_pointer_to_objref(user_handle)::Tuple{Model, Function}

Version info:
CPLEX v0.6.5
julia 1.5
JuMP 0.21.3
MOI 0.9.14

Edit: bug also observed with CPLEX 12.09

[matbesancon]

This appeared when using lazy callbacks

[matbesancon]

I seem to have another version of the bug (running the same code with CPLEX 12.08), where the error is:

   3   │ ERROR: LoadError: TypeError: in typeassert, expected Tuple{CPLEX.Model,Function}, got a value of type Core.Compiler.SlotInfo
   4   │ Stacktrace:
   5   │  [1] callback_wrapper(::Ptr{Nothing}, ::Int64, ::Ptr{Nothing}) at /home/mbesanco/.julia/packages/CPLEX/Hxpuk/src/cpx_generic_callbacks.jl:15

[odow]

This might be a Julia 1.5 change?

[matbesancon]

potentially yes, I will rerun it using 1.4 and see if it still errors

[matbesancon]

Ok the model is still running and would have errored by now, so I confirm the bug happens on 1.5 only. Sadly still no MWE I could build

[odow]

Instead of using a tuple, we probably need to define a type with an appropriate cconvert

CPLEX.jl/src/cpx_generic_callbacks.jl

Lines 48 to 53 in 02d4ef5

	user_handle = (model, callback_func)::Tuple{Model, Function}
	return_status = @cpx_ccall(
	callbacksetfunc,
	Cint,
	(Ptr{Cvoid}, Ptr{Cvoid}, Clong, Ptr{Cvoid}, Any),
	model.env, model.lp, context_mask, c_callback, user_handle

I don't know what it means to pass Any to a ccall.

[matbesancon]

do we need to pass the model? Otherwise only passing a function as Ptr{CVoid} might work?

[odow]

@matbesancon can you try #316? You'll need 12.10, however.

[matbesancon]

Yes I should be able to give it a try this weekend