# Unreachable reached at 0x7f5b7ecd6739
**URL:** https://discourse.julialang.org/t/unreachable-reached-at-0x7f5b7ecd6739/30325
**Category:** General Usage
**Created:** [October 26, 2019, 1:26am UTC](https://discourse.julialang.org/t/unreachable-reached-at-0x7f5b7ecd6739/30325 "2019-10-26T01:26:13Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@pixel27](https://discourse.julialang.org/u/pixel27)
#### Post date: [October 26, 2019, 1:26am UTC](https://discourse.julialang.org/t/unreachable-reached-at-0x7f5b7ecd6739/30325/1 "2019-10-26T01:26:13Z")
I’m probably doing some wrong, on the other hand Julia probably shouldn’t be crashing. To reproduce run this under Atom:
```julia
mutable struct Buffer
data::Vector{UInt8}
offset::Int
Buffer(val::Vector{UInt8}) = new(val, 0)
end
function Base.convert(::Type{TYPE}, val::Buffer) where TYPE
val.offset = 0
read(val, TYPE)
end
Buffer(Vector{UInt8}())
```
BTW it also crashes if your run Julia in REPL mode and include() the file. However if you run the file with `julia test.jl` everything is fine. So it’s something with the attempt to display the Buffer.
On my machine results in:
```julia
Unreachable reached at 0x7f5b7ecd6739
signal (4): Illegal instruction
in expression starting at none:0
show at ./multimedia.jl:47
#34 at /home/me/.julia/packages/Atom/X8fAI/src/display/display.jl:17
unknown function (ip: 0x7f5b8c27e739)
sprint at ./strings/io.jl:103
render at /home/me/.julia/packages/Atom/X8fAI/src/display/display.jl:16
Type at /home/me/.julia/packages/Juno/oLB1d/src/types.jl:39
Type at /home/me/.julia/packages/Juno/oLB1d/src/types.jl:40
render at /home/me/.julia/packages/Atom/X8fAI/src/display/display.jl:19
render′ at /home/me/.julia/packages/Atom/X8fAI/src/display/errors.jl:119
displayandrender at /home/me/.julia/packages/Atom/X8fAI/src/display/showdisplay.jl:137
#140 at /home/me/.julia/packages/Atom/X8fAI/src/eval.jl:151
jl_f__apply at /usr/bin/../lib/libjulia.so.1 (unknown line)
jl_f__apply_latest at /usr/bin/../lib/libjulia.so.1 (unknown line)
#invokelatest#1 at ./essentials.jl:790 [inlined]
invokelatest at ./essentials.jl:789 [inlined]
#139 at /home/me/.julia/packages/Atom/X8fAI/src/eval.jl:150
withpath at /home/me/.julia/packages/CodeTools/xGemk/src/utils.jl:30
withpath at /home/me/.julia/packages/Atom/X8fAI/src/eval.jl:47 [inlined]
#138 at /home/me/.julia/packages/Atom/X8fAI/src/eval.jl:135 [inlined]
with_logstate at ./logging.jl:395
with_logger at ./logging.jl:491 [inlined]
#137 at /home/me/.julia/packages/Atom/X8fAI/src/eval.jl:134 [inlined]
hideprompt at /home/me/.julia/packages/Atom/X8fAI/src/repl.jl:85
macro expansion at /home/me/.julia/packages/Atom/X8fAI/src/eval.jl:133 [inlined]
macro expansion at /home/me/.julia/packages/Media/ItEPc/src/dynamic.jl:24 [inlined]
#136 at /home/me/.julia/packages/Atom/X8fAI/src/eval.jl:122
handlemsg at /home/me/.julia/packages/Atom/X8fAI/src/comm.jl:164
unknown function (ip: 0x7f5b7ecb413c)
jl_f__apply at /usr/bin/../lib/libjulia.so.1 (unknown line)
#19 at ./task.jl:268
unknown function (ip: 0x7f5b7ecb0224)
unknown function (ip: 0x7f5b980d1bad)
unknown function (ip: 0xffffffffffffffff)
Allocations: 21830157 (Pool: 21825000; Big: 5157); GC: 49
```
My environment:
```julia
Julia Version 1.2.0
Commit c6da87ff4b (2019-08-20 00:03 UTC)
Platform Info:
OS: Linux (x86_64-pc-linux-gnu)
CPU: Intel(R) Core(TM) i7-3820 CPU @ 3.60GHz
WORD_SIZE: 64
LIBM: libopenlibm
LLVM: libLLVM-6.0.1 (ORCJIT, sandybridge)
Environment:
JULIA_EDITOR = atom -a
JULIA_NUM_THREADS = 4
```
The reason for the convert is that my module serializes data to disk as key/value pairs. I have setindex!/getindex implemented as a convenience method to save/load a single data object. Or the caller can use the write/read methods if multiple objects need to saved under one key.
The setindex!/getindex methods just turn around and call the write/read functions for the single object. However the getindex() method doesn’t have the type of the object being read so it just loads the bytes into a Buffer object. When Julia calls the convert() method I finally know the type and just call the read method to decode the bytes into the desired object.
I’m guessing I shouldn’t be using convert() this way…which probably means I need to add a Type parameter to getindex so I can have it decode the bytes directly? Or maybe I should be saving the type for the objects to disk so they can be loaded correctly without depending on the user saving them to the correct type, but I haven’t come across the inverse of string(typeof(val)) yet.
For now it appears if I define Base.show(io::IO, val::Buffer) I don’t get the crash.
---
### Author:  [@yuyichao](https://discourse.julialang.org/u/yuyichao)
#### Post date: [October 26, 2019, 4:26am UTC](https://discourse.julialang.org/t/unreachable-reached-at-0x7f5b7ecd6739/30325/2 "2019-10-26T04:26:45Z")
The issue you have is that the `convert` you define is way too general. On more recent version you’ll get an error instead.
```julia
julia> Buffer(Vector{UInt8}())
Error showing value of type Buffer:
ERROR: MethodError: convert(::Type{Any}, ::Buffer) is ambiguous. Candidates:
convert(::Type{Any}, x) in Base at essentials.jl:169
convert(::Type{TYPE}, val::Buffer) where TYPE in Main at REPL[2]:2
convert(::Type{T}, x::T) where T>:Union{Missing, Nothing} in Base at missing.jl:68
Possible fix, define
convert(::Type{Any}, ::Buffer)
```
---
### Author:  [@pixel27](https://discourse.julialang.org/u/pixel27)
#### Post date: [October 26, 2019, 6:22pm UTC](https://discourse.julialang.org/t/unreachable-reached-at-0x7f5b7ecd6739/30325/3 "2019-10-26T18:22:18Z")
> [@yuyichao](#):
>
> The issue you have is that the `convert` you define is way too general.
Okay, thanks. However I’m not sure how to solve that because currently I can convert it to a: Char, Int8, Int16, Int32, Int64, Int128, UInt8, UInt16, UInt32, UInt64, Float16, Float32, Float64, Bool, String, Vector{TYPE}, Vector{Any}, Set{TYPE}, Set{Any}, Dict{K, V}, Dict{Any, V}, Dict{K, Any}, Dict{Any, Any}. And I just added the ability to save/load any random data structure, so I can now convert to a user defined structure…It all depends on what data was saved.
---
### Author:  [@pixel27](https://discourse.julialang.org/u/pixel27)
#### Post date: [October 26, 2019, 11:15pm UTC](https://discourse.julialang.org/t/unreachable-reached-at-0x7f5b7ecd6739/30325/4 "2019-10-26T23:15:44Z")
Never mind, I’ve reworked the API to just export read/write I stopped fooling around getindex/setindex.