Simon Jakobi pushed to branch wip/sjakobi/nonmoving-gc-test-fixes at Glasgow Haskell Compiler / GHC Commits: 80465707 by Simon Jakobi at 2026-08-09T05:46:40+02:00 rts/js: Implement eq_thread, and test Eq/Ord ThreadId (#16761) Since d1f3c63701 (#16761), Eq ThreadId is implemented via the RTS function eq_thread, but the JS RTS never provided it, so comparing ThreadIds for equality on the JS backend crashed with ReferenceError: h$eq_thread is not defined Like the C implementation, h$eq_thread uses pointer equality: The JS RTS has exactly one thread object per thread. Previously no test exercised eq_thread directly — the 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 - - - - - 91790b45 by Simon Jakobi at 2026-08-09T05:46:40+02:00 testsuite: Make listThreads1 insensitive to the RTS's own threads listThreads1 expected `listThreads` to return exactly [ThreadId 1]. That holds only under a non-threaded RTS. Under a threaded RTS however there are more threads present, so we change the test to simply check that `myThreadId` is present in the list. Assisted-by: Claude Opus 5 - - - - - 6 changed files: - libraries/base/tests/listThreads1.hs - libraries/base/tests/listThreads1.stdout - rts/js/thread.js - + testsuite/tests/concurrent/should_run/T16761.hs - + testsuite/tests/concurrent/should_run/T16761.stdout - testsuite/tests/concurrent/should_run/all.T Changes: ===================================== libraries/base/tests/listThreads1.hs ===================================== @@ -2,5 +2,10 @@ module Main where import GHC.Conc.Sync +-- Regression test for the JS backend's ListThreadsOp, which used to omit the +-- running thread. Whatever other threads the RTS has is irrelevant here. main :: IO () -main = listThreads >>= print +main = do + tid <- myThreadId + ts <- listThreads + print (tid `elem` ts) ===================================== libraries/base/tests/listThreads1.stdout ===================================== @@ -1 +1 @@ -[ThreadId 1] +True ===================================== rts/js/thread.js ===================================== @@ -110,6 +110,10 @@ function h$rts_getThreadId(t) { // returns a CULLong RETURN_UBX_TUP2((t.tid / Math.pow(2,32))>>>0, (t.tid & 0xFFFFFFFF)>>>0); } +function h$eq_thread(t1,t2) { + return t1 === t2 ? 1 : 0; +} + function h$cmp_thread(t1,t2) { if(t1.tid < t2.tid) return -1; if(t1.tid > t2.tid) return 1; ===================================== testsuite/tests/concurrent/should_run/T16761.hs ===================================== @@ -0,0 +1,25 @@ +-- 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 ===================================== @@ -0,0 +1,6 @@ +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) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/fb53a40cc75142f4a2e6d331b983181... -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/fb53a40cc75142f4a2e6d331b983181... You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help