RootStock shipped a critical EVM-level fix that eagerly copies call data in ProgramInvokeFactoryImpl, eliminating a class of subtle bugs where shared references could cause unexpected mutation of call data during nested smart contract invocations.

# Walkthrough: Understanding the eager copy fix in ProgramInvokeFactoryImpl
# This isn't a contract you deploy — it's a node-level change.
# But you can verify the behavioral difference with a test contract.

# --- TestCallDataIntegrity.sol ---
# Deploy this on RSK testnet to confirm call data immutability
# across nested invocations.

# pragma solidity ^0.8.0;
#
# contract Inner {
#     // Returns the first 4 bytes of msg.data (the selector) and full calldata length
#     function echo() external pure returns (bytes4 selector, uint256 len, bytes memory data) {
#         selector = msg.sig;
#         len = msg.data.length;
#         data = msg.data;
#     }
# }
#
# contract Outer {
#     Inner public inner;
#
#     constructor(address _inner) {
#         inner = Inner(_inner);
#     }
#
#     // Calls Inner.echo() and then does additional memory operations
#     // to stress-test whether call data bleeds across contexts
#     function testCallDataIsolation(uint256 nonce) external view returns (
#         bytes4 innerSelector,
#         uint256 innerLen,
#         bytes memory innerData,
#         bytes4 outerSelector,
#         uint256 outerLen
#     ) {
#         // Capture outer context first
#         outerSelector = msg.sig;
#         outerLen = msg.data.length;
#
#         // Make the nested call
#         (innerSelector, innerLen, innerData) = inner.echo();
#
#         // After the nested call returns, outer's msg.data should be unchanged.
#         // Pre-fix, shared references could theoretically cause outerSelector
#         // or outerLen to reflect corrupted state in edge cases.
#         assert(msg.sig == outerSelector);       // must hold
#         assert(msg.data.length == outerLen);     // must hold
#     }
# }
#
# --- How to test ---
# 1. Deploy Inner to RSK testnet
# 2. Deploy Outer, passing Inner's address to the constructor
# 3. Call Outer.testCallDataIsolation(42)
# 4. Verify: innerSelector == 0xc5d7802e (echo's selector),
#            outerSelector == the selector for testCallDataIsolation,
#            and both lengths are correct for their respective calldata
#
# If the assertions pass (and they should post-fix), call data isolation is intact.
# On a pre-fix node with pathological execution patterns, the shared reference
# could have allowed the inner call's context setup to interfere with the outer.
#
# For node operators: verify you're running the patched RSKj release by checking
# the git log for the RSKCORE-5466 commit in ProgramInvokeFactoryImpl.java:
#   git log --oneline --all --grep="RSKCORE-5466"
# The fix is a single-line change from passing the byte array directly to:
#   Arrays.copyOf(callData, callData.length)
# in the ProgramInvoke constructor call path.