Harden rollover fee accumulation

[TUPM96]

Summary

• use checked addition when accumulating rollover fees for the same account index
• propagate arithmetic overflow instead of allowing unchecked wrapping
• add a regression test for overflow handling

Tests

• cargo test -p light-system-program-pinocchio --tests
• cargo clippy -p light-system-program-pinocchio --tests -- -D warnings

Summary by CodeRabbit

• Bug Fixes

  • Rollover fee updates now detect and report arithmetic overflow instead of silently overflowing.
  • Error propagation improved so failures setting rollover fees are returned and handled.

• Tests

  • Added unit test covering overflow during rollover fee updates to ensure state integrity.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro

Run ID: 49285a3e-478c-4076-99a4-65d4e5109909

📥 Commits

Reviewing files that changed from the base of the PR and between 0823295 and 8ff4760.

📒 Files selected for processing (1)

• programs/system/src/context.rs

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📝 Walkthrough

Walkthrough

This PR makes rollover-fee accumulation overflow-safe: SystemContext::set_rollover_fee returns Result<()> and uses checked_add to detect overflow (yielding ProgramError::ArithmeticOverflow); two processor callers now propagate that error with ?.

Changes

Rollover Fee Overflow Safety

Layer / File(s)	Summary
Rollover fee accumulation with overflow safety programs/system/src/context.rs	set_rollover_fee now returns Result<()> and uses checked_add to detect arithmetic overflow, mapping it to ProgramError::ArithmeticOverflow. A test-only new_for_test() constructor and unit test verify overflow behavior when the same index is updated repeatedly.
Error propagation in processor callers programs/system/src/processor/create_address_cpi_data.rs, programs/system/src/processor/create_outputs_cpi_data.rs	Both derive_new_addresses and create_outputs_cpi_data now use ? to propagate errors from set_rollover_fee, turning previously-ignored failures into early returns with the underlying error.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Suggested labels

ai-review

Suggested reviewers

• sergeytimoshin
• ananas-block
• SwenSchaeferjohann

Poem

🧮 Tiny fees on ledger's track,
Add with care, don't let them stack.
When totals reach the tipping line,
Trap the overflow, return the sign.
Safety first — arithmetic fine.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title directly and accurately reflects the main change: hardening rollover fee accumulation through checked arithmetic and error propagation to prevent overflow.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 70.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds checked arithmetic and error propagation when accumulating rollover fees to prevent silent u64 overflow, plus a unit test covering the overflow case.

Changes:

• Make SystemContext::set_rollover_fee return Result<()> and use checked_add with ProgramError::ArithmeticOverflow on overflow.
• Update CPI data builders to propagate set_rollover_fee errors (?).
• Add a unit test and a test-only constructor for SystemContext.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
programs/system/src/processor/create_outputs_cpi_data.rs	Propagates rollover-fee accumulation failures when building output CPI data.
programs/system/src/processor/create_address_cpi_data.rs	Propagates rollover-fee accumulation failures when deriving new address CPI data.
programs/system/src/context.rs	Implements checked fee accumulation with an overflow error, and adds a regression test.

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