printf MethodError with "append_nine_digits"

[stevengj]

This seems like a bug:

julia> using Printf

julia> @printf("%.60g", 1.38e-23)
1.3800000000000000600105824657340787992976609667826426243954e-23
julia> @printf("%.160g", 1.38e-23)
ERROR: MethodError: no method matching append_nine_digits(::Int64, ::Vector{UInt8}, ::Int64)

Closest candidates are:
  append_nine_digits(::Unsigned, ::Any, ::Int64)
   @ Base intfuncs.jl:815

Stacktrace:
 [1] writeexp(buf::Vector{…}, pos::Int64, v::Float64, precision::Int64, plus::Bool, space::Bool, hash::Bool, expchar::UInt8, decchar::UInt8, trimtrailingzeros::Bool)
   @ Base.Ryu ./ryu/exp.jl:113
 [2] writeexp(buf::Vector{…}, pos::Int64, v::Float64, precision::Int64, plus::Bool, space::Bool, hash::Bool, expchar::UInt8, decchar::UInt8, trimtrailingzeros::Bool)
   @ Base.Ryu ./ryu/exp.jl:4 [inlined]
 [3] fmt
   @ ~/Documents/Code/julia/usr/share/julia/stdlib/v1.11/Printf/src/Printf.jl:531 [inlined]
 [4] fmt
   @ ~/Documents/Code/julia/usr/share/julia/stdlib/v1.11/Printf/src/Printf.jl:313 [inlined]
 [5] format
   @ ~/Documents/Code/julia/usr/share/julia/stdlib/v1.11/Printf/src/Printf.jl:834 [inlined]
 [6] format(io::Base.TTY, f::Printf.Format{Base.CodeUnits{UInt8, String}, Tuple{Printf.Spec{Val{'g'}}}}, args::Float64)
   @ Printf ~/Documents/Code/julia/usr/share/julia/stdlib/v1.11/Printf/src/Printf.jl:935

It looks like the Unsigned type qualifier was added by @vtjnash to append_nine_digits in #51273, so it's a pretty recent problem.

[stevengj]

Looks like the culprit is the digits = 0 initializations in Ryu.writeexp, which make the digits variable type-unstable (it should always be unsigned).

In fact, @code_warntype indicates a large number of type instabilities in this function that seem undesirable (cc @quinnj):

julia> @code_warntype Base.Ryu.writeexp(UInt8[], 1, 1.0, -1, false, false, false, UInt8('e'), UInt8('.'), false)
MethodInstance for Base.Ryu.writeexp(::Vector{UInt8}, ::Int64, ::Float64, ::Int64, ::Bool, ::Bool, ::Bool, ::UInt8, ::UInt8, ::Bool)
  from writeexp(buf, pos, v::T, precision, plus, space, hash, expchar, decchar, trimtrailingzeros) where T<:Union{Float16, Float32, Float64} @ Base.Ryu ryu/exp.jl:1
Static Parameters
  T = Float64
Arguments
  #self#::Core.Const(Base.Ryu.writeexp)
  buf::Vector{UInt8}
  pos@_3::Int64
  v::Float64
  precision@_5::Int64
  plus::Bool
  space::Bool
  hash::Bool
  expchar::UInt8
  decchar::UInt8
  trimtrailingzeros::Bool
Locals
  val@_12::UInt8
  val@_13::UInt8
  val@_14::UInt16
  val@_15::Int64
  val@_16::UInt8
  val@_17::UInt8
  val@_18::UInt16
  val@_19::UInt8
  val@_20::UInt8
  val@_21::Bool
  val@_22::Bool
  val@_23::UInt8
  val@_24::Union{Int64, UInt32, UInt64}
  @_25::Union{Nothing, Tuple{Int64, Int64}}
  @_26::Union{Nothing, Tuple{Int64, Int64}}
  val@_27::UInt8
  val@_28::UInt8
  val@_29::UInt8
  val@_30::UInt8
  val@_31::UInt8
  val@_32::UInt8
  val@_33::UInt8
  val@_34::UInt8
  val@_35::UInt8
  val@_36::UInt8
  val@_37::UInt8
  @_38::Union{Nothing, Tuple{Int64, Int64}}
  val@_39::UInt8
  val@_40::UInt8
  d100::UInt16
  c::Union{Int64, UInt8}
  e::Int64
  roundPos::Int64
  roundUp::Int64
  trailingZeros::Bool
  requiredFives::Int64
  requiredTwos::Int64
  rexp::Int64
  lastDigit::Union{Int64, UInt64}
  digits::Union{Int64, UInt32, UInt64}
  maximum::Int64
  i::Union{Int64, UInt8}
  idx::Int64
  len::Int64
  p10bits::Int64
  availableDigits::Int64
  printedDigits::Int64
  nonzero::Bool
  m2::UInt64
  e2::Int64
  exp::Int64
  mant::UInt64
  bits::UInt64
  x::Float64
  startpos::Int64
  val@_67::UInt8
  val@_68::UInt8
  val@_69::UInt32
  @_70::Int64
  mulc@_71::UInt64
  mulb@_72::UInt64
  mula@_73::UInt64
  j@_74::Int64
  val@_75::UInt8
  val@_76::Union{Int64, UInt32}
  @_77::Int64
  p::Union{Int64, UInt16}
  mulc@_79::UInt64
  mulb@_80::UInt64
  mula@_81::UInt64
  j@_82::Int64
  k::Int64
  val@_84::UInt8
  val@_85::Int64
  val@_86::UInt8
  val@_87::UInt8
  val@_88::UInt8
  val@_89::UInt8
  val@_90::UInt8
  val@_91::UInt8
  pos@_92::Int64
  precision@_93::Int64
  @_94::Bool
  @_95::Int64
  @_96::Int64
  @_97::Bool
  @_98::Bool
  @_99::Int64
  @_100::Bool
  @_101::Bool
  @_102::UInt8
  @_103::Bool
Body::Int64
...

[akshaypainjane]

Hi @stevengj I modified the Ryu.writeexp function to explicitly remove the Union types and replace those variable initialization (for digits, lastDigit, c, i) with appropriate Unsigned integer datatype.

I also tried by removing all instances of the @inbounds macro from Ryu.writeexp function as I thought skipping bound checking could be the reason for the error, as @inbounds was as added in #51273

But in both the cases, the issue still remains the same.

[stevengj]

If the error remains the same, then you are passing a signed value for the digits argument, which means that you still have a type instability.

(Indeed, fixing the digits variable solved the problem. See #52781.)