Fix fixed fraction division underflow #952
Merged
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
Codecov Report
@@ Coverage Diff @@
## master #952 +/- ##
=======================================
Coverage 66.92% 66.92%
=======================================
Files 252 252
Lines 7311 7311
Branches 418 418
=======================================
Hits 4893 4893
Misses 2331 2331
Partials 87 87
Continue to review full report at Codecov.
|
m-chrzan
changed the title
mcortesi
approved these changes
Sep 14, 2019
There was a problem hiding this comment.
I didn't check the actual math. Seems reasonable though.
A few comments:
- PR description should live somewhere in the code (as comments) to avoid future changes that breaks this.
- Seeing that we now unwrap and do int division with token amounts (that have 18 decimals in eth). Maybe we should think wether it makes sense to use fixidity or define boundaries to it's use.
aaronmgdr
added a commit
that referenced
this pull request
Sep 17, 2019
* master: (132 commits) [Wallet] Differentiate dollars and gold transactions (#1021) [wip] LinkedList cycle fix (#941) Fix slither issues (#572) [Wallet] Disable import wallet button when the backup phrase is not valid (#1012) Fix fixed fraction division underflow (#952) [CircleCI]Run protocol coverage once a day (#1018) Expose and test validator set precompiles (#874) [celotool] Fund Faucet accounts on network init (#990) Add Nexmo as a text provider for MX and US numbers (#1002) [CircleCI]Run protocol test with and without coverage (#991) Increase memory requests for Alfajores nodes (#966) [wallet]Select blockchain url based on testnet (#936) Pilot app config and ability to not show testnet banner (#1009) Add Linux onboarding steps and a TOC to SETUP.md (#1004) Add README-dev.md (#989) [Wallet] Exchange flow formatting fixes (#961) [celotool] Cleanup genesis block generation (#988) [celotool] Some ❤️. Clean up (#948) CeloCLI sorted list of Validator Groups should not include groups with zero votes (#907) [contractkit] Fix tests (#963) ...
aaronmgdr
added a commit
that referenced
this pull request
Sep 18, 2019
* master: (72 commits) Remove unused Reserve.burnToken function (#984) Persistent disks for transaction nodes (#1016) [Wallet] Differentiate dollars and gold transactions (#1021) [wip] LinkedList cycle fix (#941) Fix slither issues (#572) [Wallet] Disable import wallet button when the backup phrase is not valid (#1012) Fix fixed fraction division underflow (#952) [CircleCI]Run protocol coverage once a day (#1018) Expose and test validator set precompiles (#874) [celotool] Fund Faucet accounts on network init (#990) Add Nexmo as a text provider for MX and US numbers (#1002) [CircleCI]Run protocol test with and without coverage (#991) Increase memory requests for Alfajores nodes (#966) [wallet]Select blockchain url based on testnet (#936) Pilot app config and ability to not show testnet banner (#1009) Add Linux onboarding steps and a TOC to SETUP.md (#1004) Add README-dev.md (#989) [Wallet] Exchange flow formatting fixes (#961) [celotool] Cleanup genesis block generation (#988) [celotool] Some ❤️. Clean up (#948) ... # Conflicts: # packages/web/src/header/Header.3.tsx
aaronmgdr
added a commit
that referenced
this pull request
Sep 18, 2019
* master: (38 commits) Remove unused Reserve.burnToken function (#984) Persistent disks for transaction nodes (#1016) [Wallet] Differentiate dollars and gold transactions (#1021) [wip] LinkedList cycle fix (#941) Fix slither issues (#572) [Wallet] Disable import wallet button when the backup phrase is not valid (#1012) Fix fixed fraction division underflow (#952) [CircleCI]Run protocol coverage once a day (#1018) Expose and test validator set precompiles (#874) [celotool] Fund Faucet accounts on network init (#990) Add Nexmo as a text provider for MX and US numbers (#1002) [CircleCI]Run protocol test with and without coverage (#991) Increase memory requests for Alfajores nodes (#966) [wallet]Select blockchain url based on testnet (#936) Pilot app config and ability to not show testnet banner (#1009) Add Linux onboarding steps and a TOC to SETUP.md (#1004) Add README-dev.md (#989) [Wallet] Exchange flow formatting fixes (#961) [celotool] Cleanup genesis block generation (#988) [celotool] Some ❤️. Clean up (#948) ...
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.
Description
FixidityLib's
dividecan fail when given a divisor that's large (10^24), but still small enough that it might appear naturally within Celo smart contracts. There's different ways of working around this limitation.getBuyTokenAmount(and similar) in ExchangeThis function actually returns an integer, not a fraction, so we can get better accuracy with regular integer division.
isProposalPassingin GovernanceA ratio is created for comparison with the constitution. Here we can use exact fraction arithmetic with numerators and denominators since the ratio is used only in this scope and won't have arithmetic done to it in the future, so there's no risk of future overflows.
unitsToValuein StableTokenThe inflation factor shouldn't surpass dangerous divisor size.
Quick upper-bound estimation: if annual inflation were 5% (an order of magnitude more than the current initial proposal of 0.5%), in 500 years, the inflation factor would be on the order of 10^10, which is still a safe divisor.
getUpdatedInflationFactorin StableTokendenominatoris always 10^decimalswhich is small enough.Tested
Unit tests in protocol and contractkit passing.
Other changes
Increased bucket sizes in Exchange tests to test on more realistic values.
Related issues