chore: improve error message for fsevents failure

[rgrinberg]

Include the problematic event flags in the error message

Signed-off-by: Rudi Grinberg [email protected]

ps-id: 7ab84709-6af3-433e-b337-843610bd4119

[Alizter]

Looks OK to me, but do we have a way to test it?

[rgrinberg]

I'm unable to write a test unfortunately. If I were able to write a test, I'd be able to reproduce a bug. Instead, I'm relying on @samoht to help out with triaging the issue with the help of this PR.

[samoht]

This actually makes the error message worst :-)

* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x3)
  * frame #0: 0x00000001a01ce638 libsystem_c.dylib`__vfprintf + 344
    frame #1: 0x00000001a01fd764 libsystem_c.dylib`_vsnprintf + 224
    frame #2: 0x00000001a01d9aa8 libsystem_c.dylib`__sprintf_chk + 60
    frame #3: 0x000000010032c2f0 dune`dune_fsevents_action(v_flags=<unavailable>) at fsevents_stubs.c:291:19 [opt]
    frame #4: 0x000000010034a934 dune`caml_c_call + 28
    frame #5: 0x00000001001f3120 dune`camlFsevents__action_659 + 24
    frame #6: 0x00000001001f0c84 dune`camlDune_file_watcher__fsevents_standard_event_2707 + 20
    frame #7: 0x00000001002a3614 dune`camlStdune__list__loop_481 + 76
    frame #8: 0x00000001001e6eac dune`camlDune_engine__scheduler__iter_3770 + 188
    frame #9: 0x0000000100269b30 dune`camlFiber__code_begin + 56
    frame #10: 0x00000001001e744c dune`camlDune_engine__scheduler__run_3798 + 172
    frame #11: 0x00000001001e7768 dune`camlDune_engine__scheduler__run_and_cleanup_3925 + 16
    frame #12: 0x00000001001e93a0 dune`camlDune_engine__scheduler__fun_5934 + 392
    frame #13: 0x00000001002b1148 dune`camlCmdliner_term__fun_633 + 112
    frame #14: 0x00000001002abf7c dune`camlCmdliner_eval__run_parser_537 + 44
    frame #15: 0x00000001002ad0cc dune`camlCmdliner_eval__eval_value_inner_1711 + 580
    frame #16: 0x000000010000c408 dune`camlMain__entry + 1512
    frame #17: 0x00000001000055e4 dune`caml_program + 13452
    frame #18: 0x000000010034a9a4 dune`caml_start_program + 104
    frame #19: 0x000000010032cd44 dune`caml_startup_common + 612
    frame #20: 0x000000010032cd8c dune`caml_startup + 16
    frame #21: 0x000000010032cdf0 dune`main + 16
    frame #22: 0x0000000100a7908c dyld`start + 520

instead of:

Error: exception Failure("fsevents: unexpected event action")
Raised by primitive operation at Fsevents.Event.action in file
  "src/fsevents/fsevents.ml", line 204, characters 17-31
Called from Dune_file_watcher.fsevents_standard_event in file
  "src/dune_file_watcher/dune_file_watcher.ml", line 507, characters 15-42
Called from Stdune__list.filter_map.loop in file "otherlibs/stdune/list.ml",
  line 19, characters 12-15
Called from Dune_engine__scheduler.Run_once.iter in file
  "src/dune_engine/scheduler.ml", line 1044, characters 19-25
Called from Fiber.run.loop in file "src/fiber/fiber.ml", line 15, characters
  51-60
Called from Fiber.run.(fun) in file "src/fiber/fiber.ml" (inlined), line 17,
  characters 17-47
Called from Dune_engine__scheduler.Run_once.run in file
  "src/dune_engine/scheduler.ml", line 1122, characters 10-50
Re-raised at Stdune__exn.raise_with_backtrace in file
  "otherlibs/stdune/exn.ml" (inlined), line 36, characters 27-56
Called from Dune_engine__scheduler.Run.go.(fun) in file
  "src/dune_engine/scheduler.ml", line 1358, characters 30-61
Called from Cmdliner_term.app.(fun) in file
  "vendor/cmdliner/src/cmdliner_term.ml", line 25, characters 19-24
Called from Cmdliner.Term.run in file "vendor/cmdliner/src/cmdliner.ml", line
  117, characters 32-39
Called from Cmdliner.Term.term_eval in file
  "vendor/cmdliner/src/cmdliner.ml", line 147, characters 18-36
Called from Cmdliner.Term.Group.eval in file
  "vendor/cmdliner/src/cmdliner.ml", line 367, characters 22-48
Called from Main in file "bin/main.ml", line 91, characters 10-50

[emillon]

This one is sprintf segfaulting because it's attempting to write on the format string.

[emillon]

@samoht can you try with #6215 ? that's probably unrelated but curious to check if it is.

[samoht]

With #6215 I just get:

Error: exception Failure("fsevents: unexpected event action")
Raised by primitive operation at Fsevents.Event.action in file
  "src/fsevents/fsevents.ml", line 204, characters 17-31
Called from Dune_file_watcher.fsevents_standard_event in file
  "src/dune_file_watcher/dune_file_watcher.ml", line 517, characters 15-42
Called from Stdune__list.filter_map.loop in file "otherlibs/stdune/list.ml",
  line 19, characters 12-15
Called from Dune_engine__scheduler.Run_once.iter in file
  "src/dune_engine/scheduler.ml", line 1053, characters 19-25
Called from Fiber.run.loop in file "src/fiber/fiber.ml", line 15, characters
  51-60
Called from Fiber.run.(fun) in file "src/fiber/fiber.ml" (inlined), line 17,
  characters 17-47
Called from Dune_engine__scheduler.Run_once.run in file
  "src/dune_engine/scheduler.ml", line 1131, characters 10-50
Re-raised at Stdune__exn.raise_with_backtrace in file
  "otherlibs/stdune/exn.ml" (inlined), line 36, characters 27-56
Called from Dune_engine__scheduler.Run.go.(fun) in file
  "src/dune_engine/scheduler.ml", line 1367, characters 30-61
Called from Cmdliner_term.app.(fun) in file
  "vendor/cmdliner/src/cmdliner_term.ml", line 24, characters 19-24
Called from Cmdliner_eval.run_parser in file
  "vendor/cmdliner/src/cmdliner_eval.ml", line 34, characters 37-44
Called from Cmdliner_eval.eval_value in file
  "vendor/cmdliner/src/cmdliner_eval.ml", line 202, characters 14-39
Called from Main in file "bin/main.ml", line 91, characters 10-41

I must not crash.  Uncertainty is the mind-killer. Exceptions are the
little-death that brings total obliteration.  I will fully express my cases.
Execution will pass over me and through me.  And when it has gone past, I
will unwind the stack along its path.  Where the cases are handled there will
be nothing.  Only I will remain.

[rgrinberg]

@samoht could you try again? Should be good

[samoht]

Seems better:

Error: exception Failure("fsevents: unexpected event action 3")