Allocator fixes #872
Open
Allocator fixes #872
+1,067
−65
Conversation
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
1. Improve `dbg_integrity_check`: - Add mutex protection - Fix boundary check: != instead of > - Add zero-size chunk check (prevents infinite loop) - Add minimum chunk size check - Add alignment checks for addresses and sizes - Add free list doubly-linked list integrity check - Add free list correct binning check - Fix misleading error message 2. Cleanup `Chunk` constants calculation - header_size now uses `@offsetOf(Chunk, "prior_free")` - min_size now uses `@sizeOf(Chunk)` - alignment now uses `@alignOf(Chunk)` instead of `@alignOf(Alloc)` 3. Fix bug fixes in `do_alloc` and `do_resize`: - Both functions had a bug where trailing trim could create a chunk smaller than min_size - Added check: our_new_size >= Chunk.min_size before trimming - Also changed < to <= in the trim chunk size check for correctness
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
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Outdated suggestions cannot be applied.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.
While testing out @tact1m4n3 's wifi work in #861, I got suspicious that we were relying on an allocator that hadn't actually been properly vetted. I used Claude to write a bunch of tests.
These test cases passed!
I then noticed that we could initialize the heap with a size too small for the metadata. I changed
initto return an error (API change).Finally, with Claude I looked at how
dbg_integrity_checkworks, and noticed some issues. Fixing that pointed to extra bugs which we fixed:Chunkconstants calculation@offsetOf(Chunk, "prior_free")to account for padding and to not hardcode types.@sizeOf(Chunk)so also account for potential padding, plus to not hardcode e.g. how many pointers a chunk contains.@alignOf(Chunk)instead of@alignOf(Alloc), this was just straight up incorrect, but the alignment was probably the same.do_allocanddo_resize:our_new_size >= Chunk.min_sizebefore trimming