Simon Jakobi pushed to branch wip/sjakobi/T27534 at Glasgow Haskell Compiler / GHC

Commits:

• 45299507
  by Simon Jakobi at 2026-07-22T13:25:09+02:00

  testsuite: Make T17088 an effective reproducer
  
  Initialize each byte array so that the test does not depend on
  allocator contents. Run the test only with the compacting collector and
  restore the compiler and RTS settings that trigger #17088.
  
  Disable STG lambda lifting because it removes the closure shape needed
  to reproduce the original pointer-tagging failure.
  
  Closes #27534.
  
  Assisted-by: gpt-5.6-sol via Codex CLI
  

2 changed files:

• testsuite/tests/rts/T17088.hs
• testsuite/tests/rts/all.T

Changes:

 {-# LANGUAGE MagicHash     #-}

 {-# LANGUAGE UnboxedTuples #-}

+-- Lambda lifting removes the closure shape needed to reproduce #17088.

+{-# OPTIONS_GHC -fno-stg-lift-lams #-}

+

 module Main (main) where

 import Data.Word

 bytesAllocRet :: Int -> IO Bytes

 bytesAllocRet (I# sz) =

   IO $ \s -> case newAlignedPinnedByteArray# sz 8# s of

-               (# s', mba #) -> (# s', Bytes mba #)

+               (# s', mba #) ->

+                 case writeWord8Array# mba 0# (wordToWord8# 0##) s' of

+                   s'' -> (# s'', Bytes mba #)

 ------------------------------------------------------------------------

      compile_and_run, ['RestartEventLogging_c.c'])

 test('T17088',

-     [extra_ways(['compacting_gc']), extra_run_opts('+RTS -A256k -RTS')],

-     compile_and_run, ['-rtsopts -O2'])

+     [ only_ways(['compacting_gc'])

+     , extra_ways(['compacting_gc'])

+     , extra_run_opts('+RTS -A128k -RTS')

+     ],

+     compile_and_run, ['-rtsopts -O1'])

 test('T15427', js_broken(22374), compile_and_run, [''])