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🐛 fix: restore strict overflow check in float parser #199

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Merged
ReneWerner87 merged 2 commits into from
May 15, 2026
Merged

🐛 fix: restore strict overflow check in float parser #199

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530f871
fix: restore strict overflow check in float parser
gaby May 13, 2026
527e0cc
refactor: share uint64 overflow cutoff constants
Copilot May 13, 2026
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17 changes: 8 additions & 9 deletions parse.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,11 @@ import (
"strconv"
)

const maxFracDigits = 16
const (
maxFracDigits = 16
maxUint64Cutoff = math.MaxUint64 / 10
maxUint64Cutlim = math.MaxUint64 % 10
)

type Signed interface {
~int | ~int8 | ~int16 | ~int32 | ~int64
Expand Down Expand Up @@ -136,10 +140,6 @@ func ParseUint8[S byteSeq](s S) (uint8, error) {
// It returns an error if any non-digit is encountered or overflow happens.
func parseDigits[S byteSeq](s S, i int) (uint64, error) {
var n uint64
const (
cutoff = math.MaxUint64 / 10
cutlim = math.MaxUint64 % 10
)
digits := 0
for ; i < len(s); i++ {
c := s[i] - '0'
Expand All @@ -148,7 +148,7 @@ func parseDigits[S byteSeq](s S, i int) (uint64, error) {
}
d := uint64(c)
// Any value with <= 19 digits is guaranteed to fit in uint64.
if digits >= 19 && (n > cutoff || (n == cutoff && d > cutlim)) {
if digits >= 19 && (n > maxUint64Cutoff || (n == maxUint64Cutoff && d > maxUint64Cutlim)) {
return 0, strconv.ErrRange
}
n = n*10 + d
Expand Down Expand Up @@ -245,11 +245,10 @@ func parseFloat[S byteSeq](fn string, s S) (float64, error) {
if c > 9 {
break
}
nn := intPart*10 + uint64(c)
if nn < intPart {
if intPart > maxUint64Cutoff || (intPart == maxUint64Cutoff && uint64(c) > maxUint64Cutlim) {
return 0, &strconv.NumError{Func: fn, Num: string(s), Err: strconv.ErrRange}
}
intPart = nn
intPart = intPart*10 + uint64(c)
i++
}

Expand Down
1 change: 1 addition & 0 deletions parse_test.go
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Expand Up @@ -556,6 +556,7 @@ func Test_ParseFloat64(t *testing.T) {
{strconv.FormatFloat(-math.MaxFloat64, 'g', -1, 64), -math.MaxFloat64, true},
{"5e-324", 0, true},
{"1e-400", 0, true},
{"25000000000000000000e-18", 0, false},
{"1234567891234567891234567", 0, false},
{"1.2345678912345678", 1.2345678912345678, true}, // large number
{"0.11111111111111119", 0, false},
Expand Down
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