In funC, 1 != 1

[alan890104]

Background

@ipromise2324 and I are building merkle distributor with bitmap implementation, but we find left shift operator will cause problem as it return unexpected value.

Description

When we call the is_claimed function with the index parameter set to 0, the claim_bit_index is calculated as 0 % 256, which results in claim_bit_index = 0. Consequently, int mask = 1 << 0, meaning mask = 1.

As we start using the mask variable for some comparisons, we notice an interesting situation. The mask currently equals 1, but when we compare it with mask == 1, the result dumped is 0, which is not what we expected. It should be -1, because mask = 1 and 1 == 1. Then, when we compare mask != 1, the dumped result turns out to be -1, which is also contrary to common logic.

How we solve this problem

We just simply add a division by 1 after the left shift operation, then everything goes correctly.

Enviroments

We are using @ton/blueprint": "^0.21.0

Hardware Info

MacOS (Macbook M1 pro 2021) built-in SSD.

[EmelyanenkoK]

Hi! Nice catch. Please contact us in @ton_bugs_bot (check authenticity here: https://github.com/ton-blockchain/bug-bounty) for bounty.

[Netcrepto]

Background

@ipromise2324 and I are building merkle distributor with bitmap implementation, but we find left shift operator will cause problem as it return unexpected value.

Description

When we call the is_claimed function with the index parameter set to 0, the claim_bit_index is calculated as 0 % 256, which results in claim_bit_index = 0. Consequently, int mask = 1 << 0, meaning mask = 1.

As we start using the mask variable for some comparisons, we notice an interesting situation. The mask currently equals 1, but when we compare it with mask == 1, the result dumped is 0, which is not what we expected. It should be -1, because mask = 1 and 1 == 1. Then, when we compare mask != 1, the dumped result turns out to be -1, which is also contrary to common logic.

How we solve this problem

We just simply add a division by 1 after the left shift operation, then everything goes correctly.

Enviroments

We are using @ton/blueprint": "^0.21.0

Hardware Info

MacOS (Macbook M1 pro 2021) built-in SSD.

nice position