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Simon Jakobi pushed to branch wip/sjakobi/nonmoving-gc-test-fixes at Glasgow Haskell Compiler / GHC

Commits:

fb53a40c

by Simon Jakobi at 2026-08-05T21:53:54+02:00

testsuite: Add test for Eq/Ord ThreadId (#16761)

Since d1f3c63701 (#16761), Eq ThreadId is based on thread identity via
the RTS function eq_thread, but no test exercised it directly: A missing
JS implementation was only caught incidentally by listThreads1.

Add a test covering equality, its stability across GC, and agreement
with Ord.

Assisted-by: Claude Fable 5

3 changed files:

+ testsuite/tests/concurrent/should_run/T16761.hs
+ testsuite/tests/concurrent/should_run/T16761.stdout
testsuite/tests/concurrent/should_run/all.T

Changes:

testsuite/tests/concurrent/should_run/T16761.hs

 +-- Test that Eq ThreadId is based on thread identity (eq_thread),
 +-- not on the numeric thread id, which may wrap around (#16761).
 +module Main (main) where
++
 +import Control.Concurrent
 +import System.Mem (performGC)
++
 +main :: IO ()
 +main = do
 +  t0 <- myThreadId
 +  print (t0 == t0)
++
 +  mv <- newEmptyMVar
 +  _ <- forkIO (myThreadId >>= putMVar mv)
 +  tChild <- takeMVar mv
 +  print (t0 == tChild)
 +  print (tChild == tChild)
++
 +  -- Equality must be stable even after the GC moves the TSOs.
 +  performGC
 +  print (t0 == t0)
++
 +  -- Ord must agree with Eq.
 +  print (compare t0 tChild /= EQ)
 +  print (compare t0 t0 == EQ)

testsuite/tests/concurrent/should_run/T16761.stdout

 +True
 +False
 +True
 +True
 +True
 +True

testsuite/tests/concurrent/should_run/all.T

@@ -310,6 +310,8 @@ test('hs_try_putmvar003',
  # Check forkIO exception determinism under optimization
  test('T13330', normal, compile_and_run, ['-O'])
 +test('T16761', normal, compile_and_run, [''])
++
  test('T26341', normal, compile_and_run, [''])
  # Test EINTR for async I/O interrupted by an exception (#26341)