How to write bits into a user-defined primitive type?

[ScottPJones]

This topic might also be of interest (this isn’t the first time people have wanted to use a 24-bit primitive type):

Regression between v0.6 and master with reinterpret from #21831

On v0.6.0-rc2, this works: julia> primitive type Foo 24 end ; reinterpret(Foo, b"123") 1-element Array{Foo,1}: Foo(0x333231) On v0.7.0-DEV.427, it fails: julia> primitive type Foo 24 end ; reinterpret(Foo, b"123") ERROR: ArgumentError: reinterpret from alignment 1 bytes to alignment 4 bytes not allowed Stacktrace: [1] reinterpret(::Type{Foo}, ::Array{UInt8,1}, ::Tuple{Int64}) at ./array.jl:160 [2] reinterpret(::Type{Foo}, ::Array{UInt8,1}) at ./array.jl:139 This seems to be another regres…