More robust non-integer conversions for %d Printf specifier (JuliaLan…

…g#37554)

* More robust non-integer conversions for %d Printf specifier

Fixes JuliaLang#37552. As pointed out by Jameson, the non-integer conversion code
for the `%d` specifier handling code wasn't super robust; I wasn't sure
how robust it really needed to be, since it seems a bit sketchy to me
for users to be relying on Printf conversion behavior of non-integers
with `%d` anyway; C even throws a really scary warning if you pass
non-integer for `%d`. But anyways, this isn't that much more machinery
and puts back support for printf formatting of `Rational` with `%d`
anyway. But a note to users, I'd strongly suggest doing your own
conversion, `trunc`, `round`, whatever yourself to ensure you fully
understand what's going on if you really need to use the `%d` with
non-integer arguments.

As for the issue reported, it's note quite as severe a use-case since
they're just trying to represent a _huge_ integer via `Float64`, which
seems decently reasonable.

* Add test for Rational

stdlib/Printf/src/Printf.jl

@@ -262,11 +262,17 @@ end
 end
 
 # integers
+toint(x) = x
+toint(x::Rational) = Integer(x)
+toint(x::AbstractFloat) = x > typemax(Int128) ?
+ BigInt(round(x)) : x > typemax(Int64) ?
+ Int128(round(x)) : Int64(round(x))
+
 @inline function fmt(buf, pos, arg, spec::Spec{T}) where {T <: Ints}
  leftalign, plus, space, zero, hash, width, prec =
  spec.leftalign, spec.plus, spec.space, spec.zero, spec.hash, spec.width, spec.precision
  bs = base(T)
- arg2 = arg isa AbstractFloat ? Integer(round(arg)) : arg
+ arg2 = toint(arg)
  n = i = ndigits(arg2, base=bs, pad=1)
  x, neg = arg2 < 0 ? (-arg2, true) : (arg2, false)
  arglen = n + (neg || (plus | space)) +
@@ -675,7 +681,7 @@ function plength(f::Spec{T}, x) where {T <: Strings}
 end
 
 function plength(f::Spec{T}, x) where {T <: Ints}
- x2 = x isa AbstractFloat ? Integer(round(x)) : x
+ x2 = toint(x)
  return max(f.width, f.precision + ndigits(x2, base=base(T), pad=1) + 5)
 end
 

stdlib/Printf/test/runtests.jl

@@ -429,6 +429,10 @@ end
  # 37539
  @test @sprintf(" %.1e\n", 0.999) == " 1.0e+00\n"
  @test @sprintf(" %.1f", 9.999) == " 10.0"
+
+ # 37552
+ @test @sprintf("%d", 1.0e100) == "10000000000000000159028911097599180468360808563945281389781327557747838772170381060813469985856815104"
+ @test @sprintf("%d", 3//1) == "3"
 end
 
 @testset "integers" begin