| Title | MPS LO pool: mps_arena_formatted_objects_walk fails with AVER(i < j) |
| Status | closed |
| Priority | essential |
| Assigned user | Richard Kistruck |
| Organization | Ravenbrook |
| Description | MPS LO pool: mps_arena_formatted_objects_walk fails with AVER(i < j) RHSK 2006-06-28 The mps_arena_formatted_objects_walk() call enumerates objects in all pools. If there is a pool of pool-class LO (leaf-only objects, see mps_class_lo), the mps_arena_formatted_objects_walk() call will fail with an assert. In non-asserting builds (eg. VARIETY=hi), failure mode is infinite loop in LOWalk, called from mps_arena_formatted_objects_walk. To reproduce, do this on Mac OS X: p4 sync /project/mps/branch/2006-05-31/feedback/...@159437 cd code make -f xcppgc.gmk cd ../example/hw-gc ./build Gets: MPS ASSERTION FAILURE: i < j poollo.c 465 |
| Analysis | RHSK 2006-06-28 The bug is a simple typo in the second line: next = (*format->skip)(object); next = AddrSub(object, format->headerSize); (which should read "AddrSub(next,..."). It was introduced by change 28076, which was adding format->headerSize arithmetic to poollo.c to make it support auto_header formats. Could a compiler warning have caught this? Clearly the coverage test locv.c doesn't test this: it should. RHSK 2006-06-28 Coverage test fixed: call mps_arena_formatted_objects_walk and check we find the right number of test objects. Would be nice to: 1. check that other pool classes' coverage tests do test this; 2. quick visual inspection of the diffs around change 28076. |
| How found | unknown |
| Evidence | see description. |
| Observed in | 1.106.2 |
| Introduced in | 1.100.0 |
| Created by | Richard Kistruck |
| Created on | 2006-06-28 14:47:01 |
| Last modified by | Gareth Rees |
| Last modified on | 2014-04-12 22:04:44 |
| History | 2006-06-28 RHSK Created. |
| Change | Effect | Date | User | Description |
|---|---|---|---|---|
| 159446 | closed | 2006-06-28 16:22:04 | Richard Kistruck | MPS LO pool coverage test: in stepper, mark unused args with testlib_unused() |
| 159442 | closed | 2006-06-28 15:34:07 | Richard Kistruck | MPS LO pool coverage test: call mps_arena_formatted_objects_walk and check we find the right number of test objects. |
| 159440 | closed | 2006-06-28 14:55:51 | Richard Kistruck | MPS LO pool: correct LOWalk loop increment calculation. Should fix AVER(i < j) on line 465 when you call mps_arena_formatted_objects_walk when you have objects in an LO pool. |