| Title | No interface to get collection number from a gc start message |
| Status | suspended |
| Priority | nice |
| Assigned user | Richard Brooksby |
| Organization | Ravenbrook |
| Description | The Scheme example [1] contains this code: if (type == mps_message_type_gc_start()) { printf("Collection %lu started.\n", (unsigned long)mps_collections(arena)); This is bogus because mps_collections returns the *current* count of collections for the arena, whereas what we are interested in when processing this message is the number of the collection that posted the message. |
| Analysis | I removed the collection number from this line of output (it now says just, "Collection started."). I suggest that an external interface function be added for getting the collection number from a message of type mps_message_type_gc_start(). RB suggests that mps_arena_collect, mps_arena_step, and mps_arena_park could return a collection id. This would allow you match the call against the message if you needed to do that. Also, shouldn't "mps_collections" be called "mps_arena_collections"? Maybe "mps_collections" should be deprecated? GDR 2018-07-15: What is the point of having a collection number at all? It does not seem to meet any customer use case. It could only be used for debugging or garbage collection "chatter". |
| How found | inspection |
| Evidence | [1] <https://info.ravenbrook.com/project/mps/master/example/scheme/scheme.c> |
| Observed in | 1.110.0 |
| Created by | Gareth Rees |
| Created on | 2012-10-17 17:41:22 |
| Last modified by | Gareth Rees |
| Last modified on | 2018-07-15 19:10:32 |
| History | 2012-10-17 GDR Created. 2012-10-23 GDR Added note about collect/step/park returning collection id. 2018-07-15 GDR Declined as explained in analysis. |