Files
Nim/tests/stdlib
Tomohiro 95b1dda1db Fix parseBiggestUInt to detect overflow (#24649)
With some inputs larger than `BiggestUInt.high`, `parseBiggestUInt` proc
in `parseutils.nim` fails to detect overflow and returns random value.
This is because `rawParseUInt` try to detects overflow with `if prev >
res:` but it doesn't detects the overflow from multiplication.
It is possible that `x *= 10` causes overflow and resulting value is
larger than original value.
Here is example values larger than `BiggestUInt.high` but
`parseBiggestUInt` returns without detecting overflow:
```
22751622367522324480000000
41404969074137497600000000
20701551093035827200000000000000000
22546225502460313600000000000000000
204963831854661632000000000000000000
```

Following code search for values larger than `BiggestUInt.high` and
`parseBiggestUInt` cannot detect overflow:
```nim
import std/[strutils]

const
  # Increase this to extend search range
  NBits = 34'u
  NBitsMax1 = 1'u shl NBits
  NBitsMax = NBitsMax1 - 1'u

  # Increase this when there are too many results and want to see only larger result.
  MinMultiply10 = 14

var nfound = 0
for i in (NBitsMax div 10'u + 1'u) .. NBitsMax:
  var
    x = i
    n10 = 0
  for j in 0 ..< NBits:
    let px = x
    x = (x * 10'u) and NBitsMax
    if x < px:
      break
    inc n10
  if n10 >= MinMultiply10:
    echo "i =   ", i
    echo "uint: ", (i shl (64'u - NBits)), '0'.repeat n10
    inc nfound
    if nfound > 15:
      break

echo "found: ", nfound
```
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