OffsetArray accesses out-of-bounds memory and returns an incorrect value when indexing with []

[yurivish]

It is possible that this happens due to an incorrect use of @inbounds:

julia> using OffsetArrays

julia> OffsetArray([0], 1)[]
4562921808

julia> [OffsetArray([0], 1)[] for _ in 1:10]
10-element Array{Int64,1}:
           0
  4396158144
  4582191936
  4582191936
  4396158144
           0
  4396158144
  8589934592
 12884901888
           0

julia> OffsetArray([0], 100:100)[]
4614560496

julia> versioninfo()
Julia Version 1.5.3
Commit 788b2c77c1 (2020-11-09 13:37 UTC)
Platform Info:
  OS: macOS (x86_64-apple-darwin18.7.0)
  CPU: Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-9.0.1 (ORCJIT, skylake)

[jishnub]

This is indeed due to @inbounds, but this is actually a bug in bounds-checking. However I'm not sure if the fix should be in OffsetArrays or in Base. The bounds-check in Base uses

checkbounds_indices(::Type{Bool}, IA::Tuple, ::Tuple{}) = (@_inline_meta; all(x->unsafe_length(x)==1, IA))

which seems to assume 1-based indexing.

Perhaps a fix might be added here for older Julia versions, and the main fix might go into Base.