Fix critical undefined bit-shift length operation #174
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
Natural/Integer<T>.bit() (BitRange) was shifting by whatever type the source was to match the target bit length. But this breaks when the target type is u64/s64 and the source type is u32/s32 or smaller. Shifting by >=32 becomes undefined behavior. We have to cast the input source to the target type first, so that the source<<shift result is valid. This is safe here regardless of source's signedness, because it's only used in =, &=, ^=, |= operations.
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Outdated suggestions cannot be applied.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.
Natural/Integer.bit() (BitRange) was shifting by whatever type the source was to match the target bit length.
But this breaks when the target type is u64/s64 and the source type is u32/s32 or smaller. Shifting by >=32 becomes undefined behavior.
We have to cast the input source to the target type first, so that the source<<shift result is valid.
This is safe here regardless of source's signedness, because it's only used in =, &=, ^=, |= operations.