Reject out-of-range and empty integer field values#765
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atoi/parseUInt silently overflowed on integer field values that exceed the int range: e.g. "9223372036854775808" wrapped to a negative number and "18446744073709551617" to 1, all returned with a nil error. Because atoi backs FIXInt.Read (MsgSeqNum, BodyLength, resend ranges, etc.), a malformed or oversized field silently corrupted the parsed value instead of being rejected. parseUInt now detects overflow before it happens and returns an error. atoi also length-checks its input before indexing d[0], which previously panicked on an empty integer field. Adds tests for the overflow and empty-input cases.
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Problem
atoi/parseUIntinfix_int.gobackFIXInt.Read, which parses integer FIX fields includingMsgSeqNum (34),BodyLength (9), and resend-range fields. Two issues:Silent overflow.
parseUIntaccumulatesn = n*10 + digitwith no range check, so an out-of-range value wraps silently and is returned with anilerror:"9223372036854775808"(MaxInt64+1) →-9223372036854775808"18446744073709551617"(MaxUint64+1) →1"99999999999999999999"→ wrapped garbageA malformed or oversized field (e.g. tag 34) is therefore accepted with a corrupted value instead of being rejected, which can feed wrong values into sequence-number handling.
Empty-input panic.
atoireadsd[0]before checking the length, so an empty integer field value panics withindex out of range [0] with length 0.Fix
parseUIntdetects overflow before it happens (n > (math.MaxInt-digit)/10) and returns an error.atoilength-checks its input before indexingd[0].Both keep the allocation-free hot path. Added tests for the overflow and empty-input cases; existing tests and the full package suite pass.