Segmentation fault with julia v0.6

[rdeits]

The CDDLib.jl and Polyhedra.jl unit tests fail with segfaults on Julia v0.6. The smallest reproducible example I can find so far is this:

using CDDLib
import CDDLib: Cdd_ErrorType, Cdd_boolean, @dd_ccall, Cdd_MatrixData, Cdd_rowrange,
    fulldim, myerror, myfree, CDDInequalityMatrix
using Polyhedra

A = eye(Int, 2)
b = [1, 1]
h = Polyhedra.SimpleHRepresentation(A, b)
matrix = CDDInequalityMatrix(h)
i = Cdd_rowrange(1)
len = fulldim(matrix) + 1
err = Ref{Cdd_ErrorType}(0)
certificateGMPRat = zeros(GMPRational, len)
found = (@dd_ccall Redundant Cdd_boolean (Ptr{Cdd_MatrixData{GMPRational}}, Cdd_rowrange, Ptr{GMPRational}, Ref{Cdd_ErrorType}) matrix.matrix i certificateGMPRat err)
myerror(err[])
certificate = Array{Rational{BigInt}}(certificateGMPRat)
myfree(certificateGMPRat)

which is distilled from the call to redundant(matrix, i) in test/board.jl.

Removing the final call to myfree(certificateGMPRat) prevents the segfault, but I don't understand enough about GMP to know if that's actually a good idea.

This may be related to the issue alluded to here: https://discourse.julialang.org/t/bindings-to-external-lib-work-with-0-5-but-fail-with-0-6-rc1/3734/2 . Apparently in julia v0.5, some finalizers were not actually being run, so it's possible that there's been a double-free somewhere in this code which was hidden by that v0.5 bug but revealed on v0.6.

[blegat]

Thanks for identifying this bug. It it weird because GMPRational has no finalizer. The only possible reason would be that it is freed by Rational{BigInt} which would mean that __gmp_get_num here does not copy.
Let's have the workwaround of #14 for now :)

[odow]

This should be closed as out-dated.

[odow]

julia> using CDDLib

julia> import CDDLib: Cdd_ErrorType, Cdd_boolean, @dd_ccall, Cdd_MatrixData, Cdd_rowrange,
           fulldim, myerror, myfree, CDDInequalityMatrix

julia> using Polyhedra

julia> import LinearAlgebra

julia> eye(T, n) = LinearAlgebra.I(n) * one(T)
eye (generic function with 1 method)

julia> A = eye(Int, 2)
2×2 Diagonal{Int64, Vector{Int64}}:
 1  ⋅
 ⋅  1

julia> b = [1, 1]
2-element Vector{Int64}:
 1
 1

julia> h = Polyhedra.hrep(A, b)
H-representation MixedMatHRep{Int64, Diagonal{Int64, Vector{Int64}}}:
2-element iterator of HalfSpace{Int64, Vector{Int64}}:
 HalfSpace([1, 0], 1)
 HalfSpace([0, 1], 1)

julia> matrix = CDDInequalityMatrix(h)
H-representation CDDInequalityMatrix{Rational{BigInt}, GMPRational}:
2-element iterator of HalfSpace{Rational{BigInt}, Vector{Rational{BigInt}}}:
 HalfSpace(Rational{BigInt}[1, 0], 1//1)
 HalfSpace(Rational{BigInt}[0, 1], 1//1)

julia> i = Cdd_rowrange(1)
1

julia> len = fulldim(matrix) + 1
3

julia> err = Ref{Cdd_ErrorType}(0)
Base.RefValue{Int32}(0)

julia> certificateGMPRat = zeros(GMPRational, len)
3-element Vector{GMPRational}:
 0//1
 0//1
 0//1

julia> found = (@dd_ccall Redundant Cdd_boolean (Ptr{Cdd_MatrixData{GMPRational}}, Cdd_rowrange, Ptr{GMPRational}, Ref{Cdd_ErrorType}) matrix.matrix i certificateGMPRat err)
0

julia> myerror("foo", err[])

julia> certificate = Array{Rational{BigInt}}(certificateGMPRat)
3-element Vector{Rational{BigInt}}:
 1
 2
 1

julia> myfree(certificateGMPRat)

julia>