GitLab

Zubin pushed to branch wip/9.12.3-backports at Glasgow Haskell Compiler / GHC

Commits:

01e82a3c

by Reed Mullanix at 2025-08-21T15:17:59+05:30

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

(cherry picked from commit a766286fe759251eceb304c54ba52841c2a51f86)

6 changed files:

libraries/base/changelog.md
libraries/ghc-bignum/changelog.md
libraries/ghc-bignum/src/GHC/Num/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

  # Changelog for [`base` package](http://hackage.haskell.org/package/base)
 +## 4.21.2.0 *Sept 2024*
 +  * Fix bug where `naturalAndNot` was incorrectly truncating results ([CLC proposal #350](github.com/haskell/core-libraries-committee/issues/350))
++
  ## 4.21.1.0 *Sept 2024*
    * Fix incorrect results of `integerPowMod` when the base is 0 and the exponent is negative, and `integerRecipMod` when the modulus is zero ([#26017](https://gitlab.haskell.org/ghc/ghc/-/issues/26017)).

libraries/ghc-bignum/changelog.md

@@ -4,6 +4,7 @@
  - Expose backendName
  - Add `naturalSetBit[#]` (#21173), `naturalClearBit[#]` (#21175), `naturalComplementBit[#]` (#21181)
 +- Fix bug where `naturalAndNot` was incorrectly truncating results (#26230)
  ## 1.2

libraries/ghc-bignum/src/GHC/Num/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

@@ -87,3 +87,4 @@ test('T24066', normal, compile_and_run, [''])
  test('div01', normal, compile_and_run, [''])
  test('T24245', normal, compile_and_run, [''])
  test('T25653', normal, compile_and_run, [''])
 +test('T26230', normal, compile_and_run, [''])