ton-overflow-test

Overflow Test

1. Tact itself detects whether a variable overflows, but this is limited only to the variable types provided by Tact, such as Int as uint8 (uint64, uint128, etc.)

    counter: Int as uint8;

    init() {
        self.counter = 1;
    }

    receive(msg: Mul) {
        let amount: Int = msg.amount; // msg.amount = 256
        self.counter = (self.counter * amount); // 1 * 256 > 255 -> tx will fail
    }

2. If you want to perform overflow detection for a specific Int type, you can do so through the following method.

stdlib-ext.fc

int check_fits_u7(int) asm "7 UFITS"; // You can change 7 to the number you want to detect overflow (number >= 2 ** 7 will be overflow)

FloatTest.tact

import "./imports/stdlib-ext.fc";

@name(check_fits_u7)
extends native checkU7(self: Int): Int;

    .
    .
    .

    receive(msg: Mul) {
        let amount: Int = msg.amount.checkU7(); // msg.amount = 128
        self.counter = (self.counter * amount).checkU7(); // 1 * 128 > 127 -> tx will fail
    }

Project structure

• contracts - source code of all the smart contracts of the project and their dependencies.
• wrappers - wrapper classes (implementing Contract from ton-core) for the contracts, including any [de]serialization primitives and compilation functions.
• tests - tests for the contracts.
• scripts - scripts used by the project, mainly the deployment scripts.

How to use

Build

npx blueprint build or yarn blueprint build

Test

npx blueprint test or yarn blueprint test

Deploy or run another script

npx blueprint run or yarn blueprint run

Add a new contract

npx blueprint create ContractName or yarn blueprint create ContractName

Tact-Overflow-Test