printf prints typemin(<:Signed) incorrectly

[StefanKarpinski]

julia> using Printf

julia> @sprintf "%4d" typemin(Int8)
"-/.("

julia> @sprintf "%4d" typemin(Int16)
"--.)*("

julia> @sprintf "%4d" typemin(Int32)
"-./,),(-*,("

julia> @sprintf "%4d" typemin(Int64)
"-'..--).0-*(+,))+(0("

julia> @sprintf "%4d" typemin(Int128)
"-/)0/,//(-,*0,*'.-/)-/*()-0-)/+((,/0+).("```

[Seelengrab]

julia/stdlib/Printf/src/Printf.jl

Line 295 in 9cad1e0

x, neg = arg2 < 0 ? (-arg2, true) : (arg2, false)

doesn't work for typemins:

julia> typemin(Int8)     
-128                     
                         
julia> -typemin(Int8)    
-128                     
                         
julia> abs(typemin(Int8))
-128                     

That line in Printf.jl should only be hit by integer types and floating point is handled somewhere else, right? If so, passing x through unsigned unconditionally should work, as x is assumed positive after this check anyway.

So maybe something as simple as this:

neg = arg2 < 0
x = unsigned(arg2)

since

julia> unsigned(typemin(Int8)) == 128
true

[bramtayl]

That's just the cool way of writing it