Fix bug in CycleStructurePerm for a single cycle of length 2^16 that caused wrong answers and memory corruption
#3738
Conversation
This file contains 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
ChrisJefferson
added
kind: bug: wrong result
ChrisJefferson
force-pushed
the
fix-cycle-struct-perm
branch
from
82a5c29
to
11a078a
Compare
wilfwilson
approved these changes
Nov 12, 2019
fingolfin
reviewed
Nov 13, 2019
fingolfin
approved these changes
Nov 13, 2019
CycleStructPerm overflowed a UInt2 when given a cycle of length exactly 2^16, so store the size-1 (which is what we output anyway)
ChrisJefferson
force-pushed
the
fix-cycle-struct-perm
branch
from
11a078a
to
fefc497
Compare
|
I believe all issues are now fixed |
|
Backported to stable-4.11 in commit 7d39a54 |
fingolfin
changed the title
CycleStructurePerm for a single cycle of length 2^16 that cause wrong answers and memory corruption
fingolfin
changed the title
CycleStructurePerm for a single cycle of length 2^16 that cause wrong answers and memory corruptionCycleStructurePerm for a single cycle of length 2^16 that caused wrong answers and memory corruption
fingolfin
added
release notes: added
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Outdated suggestions cannot be applied.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.
CYCLE_STRUCT_PERM overflowed a UInt2 when given a cycle of length
exactly 2^16, so store the size-1 (which is what we output anyway)
This caused both wrong answers, and memory corruption.
This function could, in principle, be overhauled/simplified to use less fancy buffers, but I'm convinced by this fix and wanted something small to go into 4.11 at least.