Mmap.mmap regression from Julia 1.10.0 to 1.10.1

[JakeZw]

I use the Raspberry PI for some work. This includes using the Package BaremetalPi to set pins high or low. This all works well with Julia 1.10.0 but not with 1.10.1. This is explained in more detail on discourse here.

The problem lies in Mmap as explained in Post 6 of the discourse link and repeated here. All commands were given on a Raspberry PI 4 with 8 Gig RAM. Julia was installed using Juliaup.

The output from 1.10.0 which is working is:

julia> versioninfo()
Julia Version 1.10.0
Commit 3120989f39b (2023-12-25 18:01 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Linux (aarch64-linux-gnu)
  CPU: 4 Ã Cortex-A72
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, cortex-a72)
  Threads: 1 on 4 virtual cores

julia> using Mmap

julia> io = open("/dev/gpiomem", "w+")
IOStream(<file /dev/gpiomem>)

julia> gpiomap = Mmap.mmap(io, Vector{UInt32}, (1024,), 0, grow=false)
1024-element Vector{UInt32}:
 0x21200900
 0x00040264
 0x12040000
 0x3fffffff
 0x00000064
 0x00000000
 0x00000000
 0x6770696f
 0x6770696f
 0x6770696f
          â®
 0x6770696f
 0x6770696f
 0x6770696f
 0x6770696f
 0x6770696f
 0x6770696f
 0x6770696f
 0x6770696f
 0x6770696f

And from 1.10.1 which errors is:

julia> versioninfo()
Julia Version 1.10.1
Commit 7790d6f0641 (2024-02-13 20:41 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Linux (aarch64-linux-gnu)
  CPU: 4 Ã Cortex-A72
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, cortex-a72)
Threads: 1 default, 0 interactive, 1 GC (on 4 virtual cores)

julia> using Mmap

julia> io = open("/dev/gpiomem", "w+")
IOStream(<file /dev/gpiomem>)

julia> gpiomap = Mmap.mmap(io, Vector{UInt32}, (1024,), 0, grow=false)
ERROR: IOError: filesize: Illegal seek for <file /dev/gpiomem>
Stacktrace:
 [1] filesize(s::IOStream)
   @ Base ./iostream.jl:226
 [2] mmap(io::IOStream, ::Type{Vector{UInt32}}, dims::Tuple{Int64}, offset::Int64; grow::Bool, shared::Bool)
   @ Mmap ~/.julia/juliaup/julia-1.10.1+0.aarch64.linux.gnu/share/julia/stdlib/v1.10/Mmap/src/Mmap.jl:215
 [3] top-level scope
   @ REPL[4]:1

Version 1.10.2 has the same issue, I have not tested on 1.10.3 release candidate.

[mkitti]

This seems likely due to #44354 which introduced a call to filesize.

[vtjnash]

That was a known correctness bug with the implementation of filesize: #48667

[ronisbr]

Hi!

Is there any known workaround? In the current state, we cannot use Julia to command the Raspberry Pi's IOs using the package BaremetalPi.jl.

[StefanKarpinski]

IMO, we shouldn't be breaking things like this in patch releases, even if it was a bug.

[tecosaur]

From triage:

• There's an optimisation to filesize that relies on seeking (see faster filesize and read(::IOStream) #35925)
• When the IO isn't seekable, this fails
• We need to handle the seek failure case properly, and fallback on calling stat