GC compaction bug

[vicuna]

Original bug ID: 5757
Reporter: markghayden
Assigned to: @damiendoligez
Status: closed (set by @damiendoligez on 2012-09-10T10:26:30Z)
Resolution: fixed
Priority: immediate
Severity: block
Version: 4.00.0
Target version: 4.00.1+dev
Fixed in version: 4.00.1+dev
Category: runtime system and C interface
Has duplicate: #6077
Related to: #5389
Monitored by: jeffsco mehdi @hcarty @dbuenzli

Bug description

The code below crashes on Linux and MacOS within a few seconds.

I believe this the root cause of a problem I have been running into with my iPad app (www.seaiq.com). The normal symptom is a segfault in invert_pointer_at in compact.c.

The problem appears to be related to the recent fix to the compactor (#5389).

Steps to reproduce

while true do ignore (String.create (Random.int 1000000)) done

File attachments

• 4.00-compaction-fix.patch

[vicuna]

Comment author: @bobzhang

could not reproduce in the toplevel, but it did happen for binary.
Could anyone explain the difference?

[vicuna]

Comment author: jeffsco

I can verify that I see the same as hongboz after building 4.00.0 under OS X 10.7.4 (Lion) with Xcode 4.3.3. A compiled version (64-bit native code or bytecode) crashes within one second with a segmentation fault. Running at toplevel shows no crash after a few minutes.

[vicuna]

Comment author: @damiendoligez

Reproduced. If you need a workaround, disable compaction and if you get fragmentation problems try the first-fit allocation policy.

[vicuna]

Comment author: @damiendoligez

Here is a patch that applies cleanly to both 4.00.0 and 4.00.1+dev. I'll commit it to the trunk and the 4.00 branch after a bit more testing.

[vicuna]

Comment author: jeffsco

I rebuilt the compiler with the patch and ran all the tests that come with the distribution. All tests passed, including pr5757:

370 test(s) passed
0 test(s) failed
0 compilation error(s)
0 compilation warning(s)
0 makefile error(s)

Xcode 4.3.3 under OSX 10.7.4 (Lion), 64-bit (2.6 GHz Intel Core i7)

[vicuna]

Comment author: @damiendoligez

Fixed in 4.00 (r 12910) and trunk (r 12912 and 12914).