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Guard out-of-bounds accesses in SisoZpk minreal #1060

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Merged
baggepinnen merged 2 commits into from
May 16, 2026
Merged

Guard out-of-bounds accesses in SisoZpk minreal #1060

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a727c2e
Guard out-of-bounds accesses in SisoZpk minreal
baggepinnen May 15, 2026
925eaa5
Add regression tests for SisoZpk minreal bounds fix
baggepinnen May 16, 2026
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3 changes: 2 additions & 1 deletion lib/ControlSystemsBase/src/types/SisoTfTypes/SisoZpk.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -79,11 +79,12 @@ function minreal(sys::SisoZpk{T,TR}, eps::Real) where {T, TR}
distance, zidx = findmin(abs.(p .- newZ))

if distance < eps
if imag(p) == 0 && imag(newZ[zidx]) != 0
if imag(p) == 0 && imag(newZ[zidx]) != 0 && zidx < length(newZ)
newZ[zidx+1] = real(newZ[zidx+1])
end
if imag(newZ[zidx]) == 0 && imag(p) != 0
pidx += 1
pidx > length(sys.p) && (deleteat!(newZ, zidx); break)
p = real(sys.p[pidx])
deleteat!(newZ, zidx)
continue
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8 changes: 8 additions & 0 deletions lib/ControlSystemsBase/test/test_zpk.jl
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Expand Up @@ -144,6 +144,14 @@ k = 0.3
@test minreal(zpk([-1.0, -2.0], Float64[], 2.5)) == zpk([-1.0, -2.0], Float64[], 2.5)
@test minreal(zpk(Float64[], [-1.0, -2.0], 2.5)) == zpk(Float64[], [-1.0, -2.0], 2.5)

# Regression: bounds-checks in SisoZpk minreal. With complex-valued zpk the
# constructor does not enforce conjugate-pair ordering, so the cancellation
# loop can hit `newZ[zidx+1]` (line 83) with `zidx == length(newZ)`, or
# advance `pidx` past `length(sys.p)` before reading `sys.p[pidx]` (line 87).
# Both previously threw BoundsError; they should now return cleanly.
@test minreal(zpk([1.0+0.001im, 1.0-0.001im], [1.0, 1.0+0.001im], 1.0+0im), 0.01) == zpk(ComplexF64[], ComplexF64[], 1.0+0im)
@test minreal(zpk([1.0+0.001im, 1.0-0.001im], [1.0+0.001im, 1.0], 1.0+0im), 0.01) == zpk(ComplexF64[], ComplexF64[], 1.0+0im)

# Test type inference
@test eltype(fill(zpk("s"),2)) <: TransferFunction
@test eltype(fill(zpk([1],[1,1],1),2)) <: TransferFunction
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