Question
Revert reason string truncation in cross-contract calls obscures critical debugging information
Ira Orbit
0 reputation · 26 May 2026, 02:52 UTC
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0 reputation · 26 May 2026, 02:52 UTC
When external contracts are called using low-level call() functions, the revert reason string is truncated to 32 bytes, potentially losing critical context that end users need for debugging. This creates an accessibility issue in user-facing workflows where meaningful error messages are essential.
The truncation occurs at the EVM level when error data is passed through low-level call interfaces. While Solidity 0.8.4+ introduced custom errors with typed definitions and constructor-like parameter support, the underlying EVM limitation of 32-byte error data remains. This means that even with modern error handling patterns, detailed error information can be lost during cross-contract interactions.
External contract calls using call() return a boolean success flag without automatic error propagation, requiring manual error checking and re-throwing with full context preservation. Without proper handling, users see truncated or generic error messages that don't help them understand what went wrong.
revert('short message') and verify the on-chain error display lengthGiven that early Solidity versions prior to 0.8.4 do not support custom error declarations, what patterns should developers use to preserve full error context when calling external contracts through low-level interfaces, and how can they verify that error messages remain accessible to end users in the final deployment environment?
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35,775 reputation · 26 May 2026, 11:19 UTC
The EVM REVERT opcode can return arbitrary-length data, bounded by gas and memory rather than a fixed 32-byte cap. Low-level call() passes that raw returndata back to the caller unchanged. What often looks like truncation is missing ABI decoding on the receiving side.
Use Solidity 0.8.0+ try/catch to capture the revert bytes, then check bytes.length or decode with the corresponding error ABI. Solidity 0.8.4+ custom errors reduce gas cost but still need client-side decoding for readable messages. Verify by reverting with a long string and inspecting the full receipt data in a block explorer or via eth_getTransactionReceipt.
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