#37997

Committed 29 Jan 2025 02:08AM UTC coverage: 17.283% (-68.7%) from 85.981%

Build # #37997

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push

local

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web-flow

Commit Message

bpart: Start enforcing min_world for global variable definitions (#57150)

This is the analog of #57102 for global variables. Unlike for consants,
there is no automatic global backdate mechanism. The reasoning for this
is that global variables can be declared at any time, unlike constants
which can only be decalared once their value is available. As a result
code patterns using `Core.eval` to declare globals are rarer and likely
incorrect.

Run Details

1 of 22 new or added lines in 3 files covered. (4.55%)

31430 existing lines in 188 files now uncovered.

7903 of 45728 relevant lines covered (17.28%)

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12.31

/stdlib/Printf/src/Printf.jl

# This file is a part of Julia. License is MIT: https://julialang.org/license
"""
The `Printf` module provides formatted output functions similar to the C standard library's `printf`. It allows formatted printing to an output stream or to a string.
"""
module Printf

using Base.Ryu

export @printf, @sprintf

public format, Format

# format specifier categories
const Ints = Union{Val{'d'}, Val{'i'}, Val{'u'}, Val{'x'}, Val{'X'}, Val{'o'}}
const Floats = Union{Val{'e'}, Val{'E'}, Val{'f'}, Val{'F'}, Val{'g'}, Val{'G'}, Val{'a'}, Val{'A'}}
const Chars = Union{Val{'c'}, Val{'C'}}
const Strings = Union{Val{'s'}, Val{'S'}}
const Pointer = Val{'p'}
const HexBases = Union{Val{'x'}, Val{'X'}, Val{'a'}, Val{'A'}}
const PositionCounter = Val{'n'}

const MAX_FRACTIONAL_PART_WIDTH = 17  # max significant decimals + 1: `ceil(Int, log10(1 / eps(Float64))) + 1`
const MAX_INTEGER_PART_WIDTH = 309  # max exponent: `ceil(Int, log10(prevfloat(typemax(Float64))))`
const MAX_FMT_CHARS_WIDTH = 5  # hash | sign +/- | decimal dot | exponent e/E | exponent sign

"""
Typed representation of a format specifier.

`T` is a `Val{'_'}`, where `_` is a valid format specifier character.

Fields are the various modifiers allowed for various format specifiers.
"""
struct Spec{T} # T => %type => Val{'type'}
    leftalign::Bool
    plus::Bool
    space::Bool
    zero::Bool
    hash::Bool
    width::Int
    precision::Int
    dynamic_width::Bool
    dynamic_precision::Bool
end

# recreate the format specifier string from a typed Spec
Base.string(f::Spec{T}; modifier::String="") where {T} =
    string("%",
           f.leftalign ? "-" : "",
           f.plus ? "+" : "",
           f.space ? " " : "",
           f.zero ? "0" : "",
           f.hash ? "#" : "",
           f.dynamic_width ? "*" : (f.width > 0 ? f.width : ""),
           f.dynamic_precision ? ".*" : (f.precision == 0 ? ".0" : (f.precision > 0 ? ".$(f.precision)" : "")),
           modifier,
           char(T))

Base.show(io::IO, f::Spec) = print(io, string(f))

floatfmt(s::Spec{T}) where {T} =
    Spec{Val{'f'}}(s.leftalign, s.plus, s.space, s.zero, s.hash, s.width, 0, s.dynamic_width, s.dynamic_precision)
ptrfmt(s::Spec{T}, x) where {T} =
    Spec{Val{'x'}}(s.leftalign, s.plus, s.space, s.zero, true, s.width, sizeof(x) == 8 ? 16 : 8, s.dynamic_width, s.dynamic_precision)

"""
    Printf.Format(format_str)

Create a C printf-compatible format object that can be used for formatting values.

The input `format_str` can include any valid format specifier character and modifiers.

A `Format` object can be passed to `Printf.format(f::Format, args...)` to produce a
formatted string, or `Printf.format(io::IO, f::Format, args...)` to print the
formatted string directly to `io`.

For convenience, the `Printf.format"..."` string macro form can be used for building
a `Printf.Format` object at macro-expansion-time.

!!! compat "Julia 1.6"
    `Printf.Format` requires Julia 1.6 or later.
"""
struct Format{S, T}
    str::S # original full format string as CodeUnits
    # keep track of non-format specifier strings to print
    # length(substringranges) == length(formats) + 1
    # so when printing, we start with printing
      # str[substringranges[1]], then formats[1] + args[1]
      # then str[substringranges[2]], then formats[2] + args[2]
      # and so on, then at the end, str[substringranges[end]]
    substringranges::Vector{UnitRange{Int}}
    formats::T # Tuple of Specs
    numarguments::Int  # required for dynamic format specifiers
end

# what number base should be used for a given format specifier?
base(T) = T <: HexBases ? 16 : T <: Val{'o'} ? 8 : 10
char(::Type{Val{c}}) where {c} = c

struct InvalidFormatStringError <: Exception
    message::String
    format::String
    start_color::Int
    end_color::Int
end

function Base.showerror(io::IO, err::InvalidFormatStringError)
    io_has_color = get(io, :color, false)::Bool

    println(io, "InvalidFormatStringError: ", err.message)
    print(io, "    \"", @view(err.format[begin:prevind(err.format, err.start_color)]))
    invalid_text = @view err.format[err.start_color:err.end_color]

    printstyled(io, invalid_text, color=:red)

    # +1 is okay, since all format characters are single bytes
    println(io, @view(err.format[err.end_color+1:end]), "\"")

    arrow_error = '-'^(length(invalid_text)-1)
    arrow = "    " * ' '^err.start_color * arrow_error * "^\n"
    if io_has_color
        printstyled(io, arrow, color=:red)
    else
        print(io, arrow)
    end
end

# parse format string
function Format(f::AbstractString)
    bytes = codeunits(f)
    len = length(bytes)
    pos = 1
    numarguments = 0

    b = 0x00
    local last_percent_pos

    # skip ahead to first format specifier
    while pos <= len
        b = bytes[pos]
        pos += 1
        if b == UInt8('%')
            last_percent_pos = pos-1
            pos > len && throw(InvalidFormatStringError("Format specifier is incomplete", f, last_percent_pos, last_percent_pos))
            if bytes[pos] == UInt8('%')
                # escaped '%'
                b = bytes[pos]
                pos += 1
            else
                break
            end
        end
    end
    strs = [1:pos - 1 - (b == UInt8('%'))]
    fmts = []
    while pos <= len
        b = bytes[pos]
        pos += 1
        # positioned at start of first format str %
        # parse flags
        leftalign = plus = space = zero = hash = false
        while true
            if b == UInt8('-')
                leftalign = true
            elseif b == UInt8('+')
                plus = true
            elseif b == UInt8(' ')
                space = true
            elseif b == UInt8('0')
                zero = true
            elseif b == UInt8('#')
                hash = true
            else
                break
            end
            pos > len && throw(InvalidFormatStringError("Format specifier is incomplete", f, last_percent_pos, pos-1))
            b = bytes[pos]
            pos += 1
        end
        if leftalign
            zero = false
        end
        # parse width
        width = 0
        dynamic_width = false
        if b == UInt8('*')
            dynamic_width = true
            numarguments += 1
            b = bytes[pos]
            pos += 1
        else
            while b - UInt8('0') < 0x0a
            width = 10 * width + (b - UInt8('0'))
                b = bytes[pos]
                pos += 1
                pos > len && break
            end
        end
        # parse precision
        precision = 0
        parsedprecdigits = false
        dynamic_precision = false
        if b == UInt8('.')
            pos > len && throw(InvalidFormatStringError("Precision specifier is missing precision", f, last_percent_pos, pos-1))
            parsedprecdigits = true
            b = bytes[pos]
            pos += 1
            if pos <= len
                if b == UInt8('*')
                    dynamic_precision = true
                    numarguments += 1
                    b = bytes[pos]
                    pos += 1
                else
                    precision = 0
                    while b - UInt8('0') < 0x0a
                        precision = 10precision + (b - UInt8('0'))
                        b = bytes[pos]
                        pos += 1
                        pos > len && break
                    end
                end
            end
        end
        # parse length modifier (ignored)
        if b == UInt8('h') || b == UInt8('l')
            prev = b
            pos > len && throw(InvalidFormatStringError("Length modifier is missing type specifier", f, last_percent_pos, pos-1))
            b = bytes[pos]
            pos += 1
            if b == prev
                pos > len && throw(InvalidFormatStringError("Length modifier is missing type specifier", f, last_percent_pos, pos-1))
                b = bytes[pos]
                pos += 1
            end
        elseif b in b"Ljqtz" # q was a synonym for ll above, see `man 3 printf`. Not to be used.
            pos > len && throw(InvalidFormatStringError("Length modifier is missing type specifier", f, last_percent_pos, pos-1))
            b = bytes[pos]
            pos += 1
        end
        # parse type
        !(b in b"diouxXDOUeEfFgGaAcCsSpn") && throw(InvalidFormatStringError("'$(Char(b))' is not a valid type specifier", f, last_percent_pos, pos-1))
        type = Val{Char(b)}
        if type <: Ints && precision > 0
            # note - we should also set zero to false if dynamic precision > 0
            # this is taken care of in fmt() for Ints
            zero = false
        elseif (type <: Strings || type <: Chars) && !parsedprecdigits
            precision = -1
        elseif type <: Union{Val{'a'}, Val{'A'}} && !parsedprecdigits
            precision = -1
        elseif type <: Floats && !parsedprecdigits
            precision = 6
        end
        numarguments += 1
        push!(fmts, Spec{type}(leftalign, plus, space, zero, hash, width, precision, dynamic_width, dynamic_precision))
        start = pos
        while pos <= len
            b = bytes[pos]
            pos += 1
            if b == UInt8('%')
                last_percent_pos = pos-1
                pos > len && throw(InvalidFormatStringError("Format specifier is incomplete", f, last_percent_pos, last_percent_pos))
                if bytes[pos] == UInt8('%')
                    # escaped '%'
                    b = bytes[pos]
                    pos += 1
                else
                    break
                end
            end
        end
        push!(strs, start:pos - 1 - (b == UInt8('%')))
    end
    return Format(bytes, strs, Tuple(fmts), numarguments)
end

macro format_str(str)
    Format(str)
end

const hex = b"0123456789abcdef"
const HEX = b"0123456789ABCDEF"

# write out a single arg according to format options
# char
@inline function writechar(buf, pos, c)
    u = bswap(reinterpret(UInt32, c))
    while true
        buf[pos] = u % UInt8
        pos += 1
        (u >>= 8) == 0 && break
    end
    return pos
end


@inline function rmdynamic(spec::Spec{T}, args, argp) where {T}
    zero, width, precision = spec.zero, spec.width, spec.precision
    if spec.dynamic_width
        width = args[argp]::Integer
        argp += 1
    end
    if spec.dynamic_precision
        precision = args[argp]::Integer
        if zero && T <: Ints && precision > 0
            zero = false
        end
        argp += 1
    end
    (Spec{T}(spec.leftalign, spec.plus, spec.space, zero, spec.hash, width, precision, false, false), argp)
end

Base.@constprop :aggressive function fmt(buf, pos, args, argp, spec::Spec{T}) where {T}
    spec, argp = rmdynamic(spec, args, argp)
    (fmt(buf, pos, args[argp], spec), argp+1)
end

function fmt(buf, pos, arg, spec::Spec{T}) where {T <: Chars}
    leftalign, width = spec.leftalign, spec.width
    c = Char(first(arg))
    w = textwidth(c)
    if !leftalign && width > w
        for _ = 1:(width - w)
            buf[pos] = UInt8(' ')
            pos += 1
        end
    end
    pos = writechar(buf, pos, c)
    if leftalign && width > w
        for _ = 1:(width - w)
            buf[pos] = UInt8(' ')
            pos += 1
        end
    end
    return pos
end

# strings
function fmt(buf, pos, arg, spec::Spec{T}) where {T <: Strings}
    leftalign, hash, width, prec = spec.leftalign, spec.hash, spec.width, spec.precision
    str = string(arg)
    slen = textwidth(str)::Int + (hash ? arg isa AbstractString ? 2 : 1 : 0)
    op = p = prec == -1 ? slen : min(slen, prec)
    if !leftalign && width > p
        for _ = 1:(width - p)
            buf[pos] = UInt8(' ')
            pos += 1
        end
    end
    if hash
        if arg isa Symbol
            buf[pos] = UInt8(':')
            pos += 1
            p -= 1
        elseif arg isa AbstractString
            buf[pos] = UInt8('"')
            pos += 1
            p -= 1
        end
    end
    for c in str
        p -= textwidth(c)
        p < 0 && break
        pos = writechar(buf, pos, c)
    end
    if hash && arg isa AbstractString && p > 0
        buf[pos] = UInt8('"')
        pos += 1
    end
    if leftalign && width > op
        for _ = 1:(width - op)
            buf[pos] = UInt8(' ')
            pos += 1
        end
    end
    return pos
end

# integers
toint(x) = x
toint(x::Rational) = Integer(x)

fmt(buf, pos, arg::AbstractFloat, spec::Spec{T}) where {T <: Ints} =
    fmt(buf, pos, arg, floatfmt(spec))

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 = toint(arg)
    n = i = ndigits(arg2, base=bs, pad=1)
    neg = arg2 < 0
    x = arg2 isa Base.BitSigned ? unsigned(abs(arg2)) : abs(arg2)
    arglen = n + (neg || (plus | space)) +
        (T == Val{'o'} && hash ? 1 : 0) +
        (T == Val{'x'} && hash ? 2 : 0) + (T == Val{'X'} && hash ? 2 : 0)
    arglen2 = arglen < width && prec > 0 ? arglen + min(max(0, prec - n), width - arglen) : arglen
    if !leftalign && !zero && arglen2 < width
        # pad left w/ spaces
        for _ = 1:(width - arglen2)
            buf[pos] = UInt8(' ')
            pos += 1
        end
    end
    if neg
        buf[pos] = UInt8('-'); pos += 1
    elseif plus # plus overrides space
        buf[pos] = UInt8('+'); pos += 1
    elseif space
        buf[pos] = UInt8(' '); pos += 1
    end
    if T == Val{'o'} && hash
        buf[pos] = UInt8('0')
        pos += 1
    elseif T == Val{'x'} && hash
        buf[pos] = UInt8('0')
        buf[pos + 1] = UInt8('x')
        pos += 2
    elseif T == Val{'X'} && hash
        buf[pos] = UInt8('0')
        buf[pos + 1] = UInt8('X')
        pos += 2
    end
    if zero && arglen2 < width
        for _ = 1:(width - arglen2)
            buf[pos] = UInt8('0')
            pos += 1
        end
    elseif n < prec
        for _ = 1:(prec - n)
            buf[pos] = UInt8('0')
            pos += 1
        end
    elseif arglen < arglen2
        for _ = 1:(arglen2 - arglen)
            buf[pos] = UInt8('0')
            pos += 1
        end
    end
    while i > 0
        @inbounds buf[pos + i - 1] = bs == 16 ?
            (T == Val{'x'} ? hex[(x & 0x0f) + 1] : HEX[(x & 0x0f) + 1]) :
            (48 + (bs == 8 ? (x & 0x07) : rem(x, 10)))
        if bs == 8
            x >>= 3
        elseif bs == 16
            x >>= 4
        else
            x = oftype(x, div(x, 10))
        end
        i -= 1
    end
    pos += n
    if leftalign && arglen2 < width
        # pad right
        for _ = 1:(width - arglen2)
            buf[pos] = UInt8(' ')
            pos += 1
        end
    end
    return pos
end

# floats
"""
    Printf.tofloat(x)

Convert an argument to a Base float type for printf formatting.
By default, arguments are converted to `Float64` via `Float64(x)`.
Custom numeric types that have a conversion to a Base float type
that wish to hook into printf formatting can extend this method like:

```julia
Printf.tofloat(x::MyCustomType) = convert_my_custom_type_to_float(x)
```

For arbitrary precision numerics, you might extend the method like:

```julia
Printf.tofloat(x::MyArbitraryPrecisionType) = BigFloat(x)
```

!!! compat "Julia 1.6"
    This function requires Julia 1.6 or later.
"""
tofloat(x) = Float64(x)
tofloat(x::Base.IEEEFloat) = x
tofloat(x::BigFloat) = x

_snprintf(ptr, siz, str, arg) =
    @ccall "libmpfr".mpfr_snprintf(ptr::Ptr{UInt8}, siz::Csize_t, str::Ptr{UInt8};
                                   arg::Ref{BigFloat})::Cint

# Arbitrary constant for a maximum number of bytes we want to output for a BigFloat.
# 8KiB seems like a reasonable default. Larger BigFloat representations should probably
# use a custom printing routine. Printing values with results larger than this ourselves
# seems like a dangerous thing to do.
const __BIG_FLOAT_MAX__ = 8192

function fmt(buf, pos, arg, spec::Spec{T}) where {T <: Floats}
    leftalign, plus, space, zero, hash, width, prec =
        spec.leftalign, spec.plus, spec.space, spec.zero, spec.hash, spec.width, spec.precision
    x = tofloat(arg)
    if x isa BigFloat
        if isfinite(x)
            GC.@preserve buf begin
                siz = length(buf) - pos + 1
                str = string(spec; modifier="R")
                required_length = _snprintf(pointer(buf, pos), siz, str, x)
                if required_length > siz
                    required_length > __BIG_FLOAT_MAX__ &&
                        throw(ArgumentError("The given BigFloat requires $required_length bytes to be printed, which is more than the maximum of $__BIG_FLOAT_MAX__ bytes supported."))
                    resize!(buf, required_length + 1)
                    required_length = _snprintf(pointer(buf, pos), required_length + 1, str, x)
                end
                required_length > 0 || throw(ArgumentError("The given BigFloat would produce less than the maximum allowed number of bytes $__BIG_FLOAT_MAX__, but still couldn't be printed fully for an unknown reason."))
                return pos + required_length
            end
        end
        x = Float64(x)
    end
    if T == Val{'e'} || T == Val{'E'}
        newpos = Ryu.writeexp(buf, pos, x, prec, plus, space, hash, char(T), UInt8('.'))
    elseif T == Val{'f'} || T == Val{'F'}
        newpos = Ryu.writefixed(buf, pos, x, prec, plus, space, hash, UInt8('.'))
    elseif T == Val{'g'} || T == Val{'G'}
        if isinf(x) || isnan(x)
            newpos = Ryu.writeshortest(buf, pos, x, plus, space)
        else
            # C11-compliant general format
            prec = prec == 0 ? 1 : prec
            # format the value in scientific notation and parse the exponent part
            exp = let p = Ryu.writeexp(buf, pos, x, prec)
                b1, b2, b3, b4 = buf[p-4], buf[p-3], buf[p-2], buf[p-1]
                Z = UInt8('0')
                if b1 == UInt8('e')
                    # two-digit exponent
                    sign = b2 == UInt8('+') ? 1 : -1
                    exp = 10 * (b3 - Z) + (b4 - Z)
                else
                    # three-digit exponent
                    sign = b1 == UInt8('+') ? 1 : -1
                    exp = 100 * (b2 - Z) + 10 * (b3 - Z) + (b4 - Z)
                end
                flipsign(exp, sign)
            end
            if -4 ≤ exp < prec
                newpos = Ryu.writefixed(buf, pos, x, prec - (exp + 1), plus, space, hash, UInt8('.'), !hash)
            else
                newpos = Ryu.writeexp(buf, pos, x, prec - 1, plus, space, hash, T == Val{'g'} ? UInt8('e') : UInt8('E'), UInt8('.'), !hash)
            end
        end
    elseif T == Val{'a'} || T == Val{'A'}
        x, neg = x < 0 || x === -Base.zero(x) ? (-x, true) : (x, false)
        newpos = pos
        if neg
            buf[newpos] = UInt8('-')
            newpos += 1
        elseif plus
            buf[newpos] = UInt8('+')
            newpos += 1
        elseif space
            buf[newpos] = UInt8(' ')
            newpos += 1
        end
        if isnan(x)
            buf[newpos] = UInt8('N')
            buf[newpos + 1] = UInt8('a')
            buf[newpos + 2] = UInt8('N')
            newpos += 3
        elseif !isfinite(x)
            buf[newpos] = UInt8('I')
            buf[newpos + 1] = UInt8('n')
            buf[newpos + 2] = UInt8('f')
            newpos += 3
        else
            buf[newpos] = UInt8('0')
            newpos += 1
            buf[newpos] = T <: Val{'a'} ? UInt8('x') : UInt8('X')
            newpos += 1
            if arg == 0
                buf[newpos] = UInt8('0')
                newpos += 1
                if prec > 0
                    buf[newpos] = UInt8('.')
                    newpos += 1
                    while prec > 0
                        buf[newpos] = UInt8('0')
                        newpos += 1
                        prec -= 1
                    end
                end
                buf[newpos] = T <: Val{'a'} ? UInt8('p') : UInt8('P')
                buf[newpos + 1] = UInt8('+')
                buf[newpos + 2] = UInt8('0')
                newpos += 3
            else
                if prec > -1
                    s, p = frexp(x)
                    sigbits = 4 * min(prec, 13)
                    s = 0.25 * round(ldexp(s, 1 + sigbits))
                    # ensure last 2 exponent bits either 01 or 10
                    u = (reinterpret(UInt64, s) & 0x003f_ffff_ffff_ffff) >> (52 - sigbits)
                    i = n = (sizeof(u) << 1) - (leading_zeros(u) >> 2)
                else
                    s, p = frexp(x)
                    s *= 2.0
                    u = (reinterpret(UInt64, s) & 0x001f_ffff_ffff_ffff)
                    t = (trailing_zeros(u) >> 2)
                    u >>= (t << 2)
                    i = n = 14 - t
                end
                frac = u > 9 || hash || prec > 0
                while i > 1
                    buf[newpos + i] = T == Val{'a'} ? hex[(u & 0x0f) + 1] : HEX[(u & 0x0f) + 1]
                    u >>= 4
                    i -= 1
                    prec -= 1
                end
                if frac
                    buf[newpos + 1] = UInt8('.')
                end
                buf[newpos] = T == Val{'a'} ? hex[(u & 0x0f) + 1] : HEX[(u & 0x0f) + 1]
                newpos += n + frac
                while prec > 0
                    buf[newpos] = UInt8('0')
                    newpos += 1
                    prec -= 1
                end
                buf[newpos] = T <: Val{'a'} ? UInt8('p') : UInt8('P')
                newpos += 1
                p -= 1
                buf[newpos] = p < 0 ? UInt8('-') : UInt8('+')
                p = p < 0 ? -p : p
                newpos += 1
                n = i = ndigits(p, base=10, pad=1)
                while i > 0
                    buf[newpos + i - 1] = 48 + rem(p, 10)
                    p = oftype(p, div(p, 10))
                    i -= 1
                end
                newpos += n
            end
        end
    end
    if newpos - pos < width
        # need to pad
        if leftalign
            # easy case, just pad spaces after number
            for _ = 1:(width - (newpos - pos))
                buf[newpos] = UInt8(' ')
                newpos += 1
            end
        else
            # right aligned
            n = width - (newpos - pos)
            if zero && isfinite(x)
                ex = (arg < 0 || (plus | space)) + (T <: Union{Val{'a'}, Val{'A'}} ? 2 : 0)
                so = pos + ex
                len = (newpos - pos) - ex
                copyto!(buf, so + n, buf, so, len)
                for i = so:(so + n - 1)
                    buf[i] = UInt8('0')
                end
                newpos += n
            else
                copyto!(buf, pos + n, buf, pos, newpos - pos)
                for i = pos:(pos + n - 1)
                    buf[i] = UInt8(' ')
                end
                newpos += n
            end
        end
    end
    return newpos
end

# pointers
fmt(buf, pos, arg, spec::Spec{Pointer}) = fmt(buf, pos, UInt64(arg), ptrfmt(spec, arg))

# position counters
function fmt(buf, pos, arg::Ref{<:Integer}, ::Spec{PositionCounter})
    arg[] = pos - 1
    pos
end

# old Printf compat
function fix_dec end
function ini_dec end

# generic fallback
function fmtfallback(buf, pos, arg, spec::Spec{T}) where {T}
    leftalign, plus, space, zero, hash, width, prec =
        spec.leftalign, spec.plus, spec.space, spec.zero, spec.hash, spec.width, spec.precision
    buf2 = Base.StringVector(
        MAX_INTEGER_PART_WIDTH + MAX_FRACTIONAL_PART_WIDTH + MAX_FMT_CHARS_WIDTH
    )
    ise = T <: Union{Val{'e'}, Val{'E'}}
    isg = T <: Union{Val{'g'}, Val{'G'}}
    isf = T <: Val{'f'}
    if isg
        prec = prec == 0 ? 1 : prec
        arg = round(arg, sigdigits=prec)
    end
    n, pt, neg = isf ? fix_dec(arg, prec, buf2) : ini_dec(arg, min(prec + ise, length(buf2) - 1), buf2)
    if isg && !hash
        while buf2[n] == UInt8('0')
            n -= 1
        end
    end
    expform = ise || (isg && !(-4 < pt <= prec))
    n2 = n + (expform ? 4 : 0) + (prec > 0 || hash) + (neg || (plus | space)) +
        (isf && pt >= n ? prec + 1 : 0)
    if !leftalign && !zero && n2 < width
        # pad left w/ spaces
        for _ = 1:(width - n2)
            buf[pos] = UInt8(' ')
            pos += 1
        end
    end
    if neg
        buf[pos] = UInt8('-'); pos += 1
    elseif plus # plus overrides space
        buf[pos] = UInt8('+'); pos += 1
    elseif space
        buf[pos] = UInt8(' '); pos += 1
    end
    if zero && n2 < width
        for _ = 1:(width - n2)
            buf[pos] = UInt8('0')
            pos += 1
        end
    end
    if expform
        buf[pos] = buf2[1]
        pos += 1
        if n > 1 || hash
            buf[pos] = UInt8('.')
            pos += 1
            for i = 2:n
                buf[pos] = buf2[i]
                pos += 1
            end
        end
        buf[pos] = T <: Val{'e'} || T <: Val{'g'} ? UInt8('e') : UInt8('E')
        pos += 1
        exp = pt - 1
        buf[pos] = exp < 0 ? UInt8('-') : UInt8('+')
        pos += 1
        exp = abs(exp)
        if exp < 10
            buf[pos] = UInt8('0')
            buf[pos + 1] = 48 + exp
            pos += 2
        else
            buf[pos] = 48 + div(exp, 10)
            buf[pos + 1] = 48 + rem(exp, 10)
            pos += 2
        end
    elseif pt <= 0
        buf[pos] = UInt8('0')
        buf[pos + 1] = UInt8('.')
        pos += 2
        while pt < 0
            buf[pos] = UInt8('0')
            pos += 1
            pt += 1
        end
        for i = 1:n
            buf[pos] = buf2[i]
            pos += 1
        end
    elseif pt >= n
        for i = 1:n
            buf[pos] = buf2[i]
            pos += 1
        end
        while pt > n
            buf[pos] = UInt8('0')
            pos += 1
            n += 1
        end
        if hash || (isf && prec > 0)
            buf[pos] = UInt8('.')
            pos += 1
            while prec > 0
                buf[pos] = UInt8('0')
                pos += 1
                prec -= 1
            end
        end
    else
        for i = 1:pt
            buf[pos] = buf2[i]
            pos += 1
        end
        buf[pos] = UInt8('.')
        pos += 1
        for i = pt+1:n
            buf[pos] = buf2[i]
            pos += 1
        end
    end

    if leftalign && n2 < width
        # pad right
        for _ = 1:(width - n2)
            buf[pos] = UInt8(' ')
            pos += 1
        end
    end
    return pos
end

const UNROLL_UPTO = 16
# if you have your own buffer + pos, write formatted args directly to it
@inline function format(buf::Vector{UInt8}, pos::Integer, f::Format, args...)
    # write out first substring
    escapechar = false
    for i in f.substringranges[1]
        b = f.str[i]
        if !escapechar
            buf[pos] = b
            pos += 1
            escapechar = b === UInt8('%')
        else
            escapechar = false
        end
    end
    # for each format, write out arg and next substring
    # unroll up to 16 formats
    N = length(f.formats)
    argp = 1
    Base.@nexprs 16 i -> begin
        if N >= i
            pos, argp = fmt(buf, pos, args, argp, f.formats[i])
            for j in f.substringranges[i + 1]
                b = f.str[j]
                if !escapechar
                    buf[pos] = b
                    pos += 1
                    escapechar = b === UInt8('%')
                else
                    escapechar = false
                end
            end
        end
    end
    if N > 16
        for i = 17:length(f.formats)
            pos, argp = fmt(buf, pos, args, argp, f.formats[i])
            for j in f.substringranges[i + 1]
                b = f.str[j]
                if !escapechar
                    buf[pos] = b
                    pos += 1
                    escapechar = b === UInt8('%')
                else
                    escapechar = false
                end
            end
        end
    end
    return pos
end

@inline function plength(f::Spec{T}, args, argp) where {T}
    f, argp = rmdynamic(f, args, argp)
    (plength(f, args[argp]), argp+1)
end

function plength(f::Spec{T}, x) where {T <: Chars}
    c = Char(first(x))
    w = textwidth(c)
    return max(f.width, w) + (ncodeunits(c) - w)
end

plength(f::Spec{Pointer}, x) = max(f.width, 2 * sizeof(x) + 2)

function plength(f::Spec{T}, x) where {T <: Strings}
    str = string(x)
    sw = textwidth(str)
    p = f.precision == -1 ? (sw + (f.hash ? (x isa Symbol ? 1 : 2) : 0)) : f.precision
    return max(f.width, p) + (sizeof(str) - sw)
end

function plength(f::Spec{T}, x) where {T <: Ints}
    x2 = toint(x)
    return max(
        f.width,
        f.precision + ndigits(x2, base=base(T), pad=1) + MAX_FMT_CHARS_WIDTH
    )
end

plength(f::Spec{T}, x::AbstractFloat) where {T <: Ints} =
    max(f.width, f.hash + MAX_INTEGER_PART_WIDTH + 0 + MAX_FMT_CHARS_WIDTH)
plength(f::Spec{T}, x) where {T <: Floats} =
    max(f.width, f.hash + MAX_INTEGER_PART_WIDTH + f.precision + MAX_FMT_CHARS_WIDTH)
plength(::Spec{PositionCounter}, x) = 0

@inline function computelen(substringranges, formats, args)
    len = sum(length, substringranges)
    N = length(formats)
    # unroll up to 16 formats
    argp = 1
    Base.@nexprs 16 i -> begin
        if N >= i
            l, argp = plength(formats[i], args, argp)
            len += l
        end
    end
    if N > 16
        for i = 17:length(formats)
            l, argp = plength(formats[i], args, argp)
            len += l
        end
    end
    return len
end

@noinline argmismatch(a, b) =
    throw(ArgumentError("Number of format specifiers and number of provided args differ: $a != $b"))

"""
    Printf.format(f::Printf.Format, args...) => String
    Printf.format(io::IO, f::Printf.Format, args...)

Apply a printf format object `f` to provided `args` and return the formatted string
(1st method), or print directly to an `io` object (2nd method). See [`@printf`](@ref)
for more details on C `printf` support.
"""
function format end

# Since it will specialize on `f`, which has a Tuple-type often of length(args), we might as well specialize on `args` too.
function format(io::IO, f::Format, args::Vararg{Any,N}) where N # => Nothing
    f.numarguments == length(args) || argmismatch(f.numarguments, length(args))
    buf = Base.StringVector(computelen(f.substringranges, f.formats, args))
    pos = format(buf, 1, f, args...)
    write(io, resize!(buf, pos - 1))
    return
end

function format(f::Format, args::Vararg{Any,N}) where N # => String
    f.numarguments == length(args) || argmismatch(f.numarguments, length(args))
    buf = Base.StringVector(computelen(f.substringranges, f.formats, args))
    pos = format(buf, 1, f, args...)
    return String(resize!(buf, pos - 1))
end

"""
    @printf([io::IO], "%Fmt", args...)

Print `args` using C `printf` style format specification string.
Optionally, an `IO` may be passed as the first argument to redirect output.

# Examples
```jldoctest
julia> @printf "Hello %s" "world"
Hello world

julia> @printf "Scientific notation %e" 1.234
Scientific notation 1.234000e+00

julia> @printf "Scientific notation three digits %.3e" 1.23456
Scientific notation three digits 1.235e+00

julia> @printf "Decimal two digits %.2f" 1.23456
Decimal two digits 1.23

julia> @printf "Padded to length 5 %5i" 123
Padded to length 5   123

julia> @printf "Padded with zeros to length 6 %06i" 123
Padded with zeros to length 6 000123

julia> @printf "Use shorter of decimal or scientific %g %g" 1.23 12300000.0
Use shorter of decimal or scientific 1.23 1.23e+07

julia> @printf "Use dynamic width and precision  %*.*f" 10 2 0.12345
Use dynamic width and precision        0.12
```
For a systematic specification of the format, see [here](https://en.cppreference.com/w/c/io/fprintf).
See also [`@sprintf`](@ref) to get the result as a `String` instead of it being printed.

# Caveats
`Inf` and `NaN` are printed consistently as `Inf` and `NaN` for flags `%a`, `%A`,
`%e`, `%E`, `%f`, `%F`, `%g`, and `%G`. Furthermore, if a floating point number is
equally close to the numeric values of two possible output strings, the output
string further away from zero is chosen.

# Examples
```jldoctest
julia> @printf("%f %F %f %F", Inf, Inf, NaN, NaN)
Inf Inf NaN NaN

julia> @printf "%.0f %.1f %f" 0.5 0.025 -0.0078125
0 0.0 -0.007812
```

!!! compat "Julia 1.8"
    Starting in Julia 1.8, `%s` (string) and `%c` (character) widths are computed
    using [`textwidth`](@ref), which e.g. ignores zero-width characters
    (such as combining characters for diacritical marks) and treats certain
    "wide" characters (e.g. emoji) as width `2`.

!!! compat "Julia 1.10"
    Dynamic width specifiers like `%*s` and `%0*.*f` require Julia 1.10.
"""
macro printf(io_or_fmt, args...)
    if io_or_fmt isa String
        fmt = Format(io_or_fmt)
        return esc(:($Printf.format(stdout, $fmt, $(args...))))
    else
        io = io_or_fmt
        isempty(args) && throw(ArgumentError("No format string provided to `@printf` - use like `@printf [io] <format string> [<args...>]."))
        fmt_str = first(args)
        fmt_str isa String || throw(ArgumentError("First argument to `@printf` after `io` must be a format string"))
        fmt = Format(fmt_str)
        return esc(:($Printf.format($io, $fmt, $(Base.tail(args)...))))
    end
end

"""
    @sprintf("%Fmt", args...)

Return [`@printf`](@ref) formatted output as string.

# Examples
```jldoctest
julia> @sprintf "this is a %s %15.1f" "test" 34.567
"this is a test            34.6"
```
"""
macro sprintf(fmt, args...)
    fmt isa String || throw(ArgumentError("First argument to `@sprintf` must be a format string."))
    f = Format(fmt)
    return esc(:($Printf.format($f, $(args...))))
end

end # module

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