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Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC

Commits:

a766286f

by Reed Mullanix at 2025-08-13T21:04:36-04:00

ghc-internal: Fix naturalAndNot for NB/NS case

When the first argument to `naturalAndNot` is larger than a `Word` and the second is `Word`-sized, `naturalAndNot` will truncate the
result:

```
>>> naturalAndNot ((2 ^ 65) .|. (2 ^ 3)) (2 ^ 3)
0
```

In contrast, `naturalAndNot` does not truncate when both arguments are larger than a `Word`, so this appears to be a bug.
Luckily, the fix is pretty easy: we just need to call `bigNatAndNotWord#` instead of truncating.

Fixes #26230

6 changed files:

libraries/base/changelog.md
libraries/ghc-bignum/changelog.md
libraries/ghc-internal/src/GHC/Internal/Bignum/Natural.hs
+ testsuite/tests/numeric/should_run/T26230.hs
+ testsuite/tests/numeric/should_run/T26230.stdout
testsuite/tests/numeric/should_run/all.T

Changes:

libraries/base/changelog.md

@@ -5,6 +5,7 @@
    * Fix issues with toRational for types capable to represent infinite and not-a-number values ([CLC proposal #338](https://github.com/haskell/core-libraries-committee/issues/338))
    * Modify the implementation of `Data.List.sortOn` to use `(>)` instead of `compare`. ([CLC proposal #332](https://github.com/haskell/core-libraries-committee/issues/332))
    * `GHC.Exts.IOPort#` and its related operations have been removed  ([CLC #213](https://github.com/haskell/core-libraries-committee/issues/213))
 +  * Fix bug where `naturalAndNot` was incorrectly truncating results ([CLC proposal #350](github.com/haskell/core-libraries-committee/issues/350))
  ## 4.22.0.0 *TBA*
    * Shipped with GHC 9.14.1

libraries/ghc-bignum/changelog.md

@@ -5,6 +5,8 @@
  - `ghc-bignum`'s implementation has been merged into `ghc-internal`.
    Downstream users should import `GHC.Num.{Integer,Natural,BigNat}` stable
    modules from `base` instead.
 +- Fix bug where `naturalAndNot` was incorrectly truncating results (#26230)
++
  ## 1.3

libraries/ghc-internal/src/GHC/Internal/Bignum/Natural.hs

@@ -488,7 +488,7 @@ naturalAndNot :: Natural -> Natural -> Natural
  {-# NOINLINE naturalAndNot #-}
  naturalAndNot (NS n) (NS m) = NS (n `and#` not# m)
  naturalAndNot (NS n) (NB m) = NS (n `and#` not# (bigNatToWord# m))
 -naturalAndNot (NB n) (NS m) = NS (bigNatToWord# n `and#` not# m)
 +naturalAndNot (NB n) (NS m) = NB (bigNatAndNotWord# n m)
  naturalAndNot (NB n) (NB m) = naturalFromBigNat# (bigNatAndNot n m)
  naturalOr :: Natural -> Natural -> Natural

testsuite/tests/numeric/should_run/T26230.hs

 +import Data.Bits
 +import GHC.Num.Natural
++
 +main = do
 +  print $ naturalAndNot ((2 ^ 4) .|. (2 ^ 3)) (2 ^ 3)
 +  print $ naturalAndNot ((2 ^ 129) .|. (2 ^ 65)) (2 ^ 65)
 +  print $ naturalAndNot ((2 ^ 4) .|. (2 ^ 3)) ((2 ^ 65) .|. (2 ^ 3))
 +  print $ naturalAndNot ((2 ^ 65) .|. (2 ^ 3)) (2 ^ 3)

testsuite/tests/numeric/should_run/T26230.stdout

 +16
 +680564733841876926926749214863536422912
 +16
 +36893488147419103232

testsuite/tests/numeric/should_run/all.T

@@ -88,3 +88,4 @@ test('div01', normal, compile_and_run, [''])
  test('T24245', normal, compile_and_run, [''])
  test('T25653', normal, compile_and_run, [''])
  test('T18619', exit_code(1), compile_and_run, [''])
 +test('T26230', normal, compile_and_run, [''])