Record hidden ptr in layout#92
Merged
udesou merged 3 commits intommtk:mmtk-support-moving-upstreamfrom Aug 5, 2025
Merged
Conversation
Member
Author
|
@d-netto Can you review the PR? This PR just shows one way about how we can get the offsets of those 'hidden pointers', and it shows it is necessary for Julia to provide offsets of those pointers to GC impls. The actual implementation would be need to be discussed with Julia devs. The current implementation is not meant to be upstreamed. |
udesou
approved these changes
Aug 5, 2025
udesou
pushed a commit
to udesou/julia
that referenced
this pull request
Aug 6, 2025
* Add fields about hidden pointers in jl_datatype_layout_t * Record hidden pointer in layout * Move the new field to the end of the struct
qinsoon
added a commit
that referenced
this pull request
Feb 9, 2026
* Add fields about hidden pointers in jl_datatype_layout_t * Record hidden pointer in layout * Move the new field to the end of the struct
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
This PR records the hidden pointer offsets in
jl_datatype_layout_t. Hidden pointers are fields likeptr_or_offsetinjl_genericmemoryref_t, which is not recorded as a pointer but actually may be heap (internal) pointers.There might be other types of hidden pointers. Currently we assume the recorded hidden pointers are all like
ptr_or_offset-- a union of an internal pointer, or an integer.The current implementation adds
hiddenptrfieldstojl_typename_t, and specifically definehiddenptrfieldsforjl_genericmemoryref_t. This is not an ideal solution. I think a better solution would be to introduce a new type that represents a hidden pointer, and use the type for fields likeptr_or_offset. However, I am not familiar with Julia's type system, and didn't get it to work. The current approach usinghiddenptrfieldsis a workaround.