Class CellBounds

A detector that identifies cell overflow and underflow problems.

Why is it bad?

Cell overflow and underflow are issues specific to the TON blockchain. TON stores data in cells, which are low-level data structures used for serialization and deserialization.

The overflow issue occurs when the user attempts to store more data in a cell than it supports. The current limitation is 1023 bits and 4 references to other cells. When these limits are exceeded, the contract throws an error with the exit code 8 during the compute phase.

The underflow issue occurs when the user attempts to get more data from a structure than it supports. cells. When it happens, the contract throws an error with the exit code 9 during the compute phase.

Example

// Bad: storeRef is used more than 4 times
beginCell()
  .storeRef(...)
  .storeAddress(myAddress())
  .storeRef(...)
  .storeRef(...)
  .storeRef(...)
  .storeRef(...)
  .endCell()
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Use instead:

// OK: Fixed after the analyzer highlighted it
beginCell()
  .storeRef(...)
  .storeAddress(myAddress())
  .storeRef(...)
  .storeRef(...)
  .storeRef(...)
  .endCell()
Copy

Resources

1. Cell & Bag of Cells (BoC) | TON Docs
2. TVM Exit codes | TON Docs
3. Cells, Builders and Slices | Tact Docs