Questions tagged [library]

Libraries are reusable code. In the context of smart contracts, they are deployed only once at a specific address and their code is reused using DELEGATECALL.

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How to deploy Library contract separate from the main contract and link it

For deployment I am using remix. When I deploy Hello.sol the compiler typically merges SafeMath.sol as a part of the main contract (Hello.sol) and deploys. This adds up library and main contract's ...
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Ethereum linking library with contract not working as accepted…returning any state variable returns just the default value

my library pragma solidity ^0.5.8; library SafeMath { function add(uint256 a,uint256 b) public pure returns (uint256) { return a+b; } } My contract pragma solidity ^0.5.8; import ...
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pass storage through interface to library

Here is what am i doing: There is a library, accept storage argument as parameter, then do some math and return the result. And there is a contract to call the function in the library, and an extra ...
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1answer
96 views

Solidity modifiers in library?

Isn't it possible to define modifiers in libraries? I'm really asking myself why, because thats some functionality you would need over and over again. If I would like to hypothetically implement some ...
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1answer
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Link library to contract without migrations

To link library in migrations I use: await deployer.deploy(MyTokenL) await deployer.link(MyTokenL, MyToken) We want to use migrations as infrastructure deployment and then have a deployment factory ...
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Can a library use another library?

Is it possible to use a library within a library? library L2 { //... } library L1 { using L2 for *; //... } This compiles and runs just fine but what I really want to know is if L1 is ...
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getting error error TypeError: Member “isContract” not found or not visible after argument-dependent lookup in address payable

Using Solidity 0.4.17, I have defined a simple library at ./Addresses.sol function isContract(address _base) external pure returns(bool) { assembly { _r := gt(extcodesize(_base), 0) ...
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Can I import a Library from a Library?

Is it possible to import a library into another library? I give a simplified example below of what I'd like to achieve: library structLib { struct Point { uint X; uint Y; } } ...
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1answer
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unable to understand how to use internal function types

I need help to understand below code which is from solidity offical documents "how to use internal function types". as it is very confusing for me. How to use library in solidity. Some one explain ...
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1answer
61 views

Why does this function not need a require statement?

Why does the following function not need a require statment? function transferFrom(address from, address to, uint256 value) public returns (bool) { _allowed[from][msg.sender] = _allowed[from][...
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Ethereum js wallet for php

https://github.com/ethereumjs/ethereumjs-wallet I need this library with the same functions in PHP Would u give me the link
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2answers
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Is library use inherited?

When a base class uses a library, do derived classes also use the same library? For example: contract A { using SafeMath for uint256; ... } contract B is A { //is code here using ...
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0answers
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Can I call a library function from a payable function?

I seem to get a revert each time I try this. I'm unable to get any useful revert message from truffle, so any assistance there might also help solve this. I have a library: library LibInterface { ....
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1answer
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Why won't remix finish launching all of my libraries?

I've run into an issue. I have a contract with a hierarchy of libraries (some lower level libraries import higher level libraries). All libraries are ultimately imported by our main contract. ...
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1answer
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How does a contract know which library to query or know the library address?

How does a contract know which library to query? For Example in the code below (The code is from solidity docs: https://solidity.readthedocs.io/en/v0.4.24/contracts.html?highlight=library#libraries ...
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How to use delegate call with external Library contract?

Here is my Library Contract deployed at 0xdeadbeef: library UsefulLib { function caculateAddress(address origin, uint nonce) pure external returns (address) { if(nonce == 0x00)...
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Understanding Solidity Libraries using Solidity Docs code example

I was going through this code (see code below) about how to use libraries in solidity docs : https://solidity.readthedocs.io/en/v0.4.24/contracts.html?highlight=library#libraries and there are some ...
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2answers
173 views

Publishing contracts with libraries using web3.py

Im trying to publish contracts with libraries in them and im getting the below issue. Contracts without libraries publish just fine. Can someone who might have faced this issue before advise what the ...
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How to verify a contract with libraries deployed from Remix

I successfully deployed a contract with remix here on Ropsten Testnet: https://ropsten.etherscan.io/address/0x10273a926517b417015748da21e1287bab2da8f7 The Source Code is very simple but I'm using my ...
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1answer
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Solidity SafeMath library best practice use cases

I understand why and how to use the SafeMath library. However, I was wondering if there is a kind of best practice guide how and when to use the library and in which cases you don't have to. From a ...
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1answer
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Unable to retrieve struct from mapping

I have a mapping like this: pragma solidity 0.4.24; pragma experimental ABIEncoderV2; pragma experimental "v0.5.0"; ... mapping(bytes32 => LibMarket.Market) public hashToMarket; where each ...
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0answers
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Which solidity dev environments support the use of already deployed library contracts?

So, I'm looking into using libraries in order to prevent re-deployment/re-use of the same code. I was hoping that I would be able to specify the address of a library in solidity code, using syntax ...
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1answer
135 views

Library function overloading

I have 3 libraries, one exposes struct and 2 others expose method with same signature/return type (first one provides default method implementation and second - extended and customized one). When ...
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1answer
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Trouble with libraries (Remix)

Tried out libraries for the first time, had a really bad experience with them. I need some help in getting my contracts to work between libraries. Library 1: pragma solidity ^0.4.0; library ...
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1answer
194 views

Upradeable proxy library throws on any function, how to connect proxy and maincontract

I'm trying to implement a proxy library through the techniques researched by openZeppelin using proxies. I have 4 contracts 1. Library with logic 2. Library containing the interface for the logic ...
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1answer
401 views

Using a library to change storage

I'm trying to learn about using libraries in solidity. In the following test contract, swapNumberLib does not successfully set value1 = value2. I thought libraries could act on the storage of a ...
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0answers
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delegatecall on library always run out of gas

I'm trying to replicate the Dynamic Library attack of this paper under a recent version of solidity and the EVM. Streamlining down the code, I've created this very simple contract (which is, in ...
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1answer
161 views

OpenZeppelin ECRecovery does not work

I am trying to use the OpenZeppelin ECRecovery library for a project I am working on. Unfortunately I don't fully understand how it works and there's no documentation for it. Let's say I want to ...
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1answer
127 views

Contract libraries structure

I have pretty big smart contract with a lot of structs. Each struct has in average 3-4 related methods (i.e. methods with first parameter MyLibrary.MyType storage self). Question about code ...
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Can paritytech/parity be used as a library the same way that go-ethereum can be used in Go?

The go-ethereum project is divided into a set of standalone libraries that can be used in any Go project (e.g. smart contract interaction, keystore management, common cryptography and hex utils) Can ...
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2answers
533 views

SafeMath library vs SafeMath contract on the inheritance chain

guys, I am developing ERC-20 token and I am wondering why SafeMath is used as as library in the OpenZeppelin implementation? Will not it be more optimal if we supply it as a base contract on the ...
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2answers
897 views

Can I define global variables in Library contract?

I want to use some variables in multiple functions in my library contract. Is there any way to do that? I got following error code for my library code. library myArithmetic { bytes1[10] mData; ...
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1answer
53 views

Using 3rd party libraries in production

In the case where you wish to use a library that someone else has written for your own contract, is it generally best practice to link to the developer's own deployment of their library? Or should you ...
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0answers
108 views

Solidity libraries with public visibility

Suppose I have the following Contracts and a Library: pragma solidity ^0.4.21; library UserLib { function insertUser(address dbAddr, bytes32 user) public { DB(dbAddr).setUser(user); } } ...
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1answer
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Error: invalid solidity type!: (library.enum)

Consider the following sample Truffle project: . ├── contracts │   ├── Foo.sol │   └── Migrations.sol ├── migrations │   ├── 1_initial_migration.js │   └── 2_foo.js ├── test │   └── Foo.test.js └── ...
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1answer
319 views

Is it possible to use a solidity library inside another?

I am trying to use a solidity library inside another. The minimal code would be something like this: The deepest library: SLib.sol pragma solidity ^0.4.18; library SLib { struct SCtx { uint a;...
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1answer
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Difference between library-using-for and contract-is

I am using two different ways to get the same result and wondering what the real difference is. Both options (library, using, for and contract, is)deliver just an extended code from a file. Method no ...
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0answers
208 views

Benefits of library versus a plain contract (upgradeability)

I'm trying to find what the benefit is of a library. I found the following statements. (Please correct me if i'm wrong) Cost less gas to deploy Uses the storage of the calling contract the library ...
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1answer
380 views

Reputable Solidity utils library for arrays

Is there an audited and reputable smart contracts utils library with helpers for dealing with arrays? I haven't found anything great on Google so far.
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2answers
698 views

@dev and @title in solidity [duplicate]

When we use built-in library in solidity smart contract, why we need to use @dev and @title annotation? My code is like below: /** *@title SafeMath *@dev Math operations with safety checks that ...
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1answer
76 views

Building Ethereum application with in-process client

Most applications connect to an Ethereum Node through RPC, using a library like Web3.js and Nethereum. That introduces a need to deploy a full node side-by-side with the application, be it on the ...
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0answers
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How to create a contract B that calls a library via contract A

As I understand it, the logic to deploy contract that uses library is as below: supposed that MetaCoin contract use TestLib library Deploy TestLib library first, then get a library contract address ...
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1answer
326 views

Library gets automatically included in contract

environment: all contracts use pragma solidity ^0.4.17; the compiler is 0.4.18+commit.9cf6e910.Emscripten.clang OS is MacOS X My token contract uses a Math library that is defined like so library ...
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1answer
148 views

Library function access-level

I have a contract A, which has an instance of contract B, i.e., B b. Contract A calls a function of contract B via the instance, i.e., b.func(). Contract B is stateless, i.e., no global non-constant ...
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1answer
889 views

link libraries with smart contracts

I have created library and imported in my contract. I am not able to link the library in deployment file. solution needed. thanks in adv pragma solidity ^0.4.2; library StringUtils { /// @dev ...
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0answers
85 views

What's the value of `this` inside a library function when called via a delegatecall?

Imagine a contract C that makes a delegatecall to a library L. C -> L What's the value of this inside L: address(C) or address(L) ? If now that L makes a normal call to another contract D. C ->...
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1answer
393 views

Importing a contract from GitHub

I'm trying to import a contract from GitHub: pragma solidity ^0.4.18; pragma experimental ABIEncoderV2; pragma experimental "v0.5.0"; import "github.com/ethereum/dapp-bin/library/stringUtils.sol"; ...
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How to import libraries to Mist? [duplicate]

I've create a contract in Remix imporing 2 differents libreries and it works ok, but when I copy and paste it into Mist I got an error at the import statement. Code goes like this: pragma solidity ^...
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1answer
213 views

Help to understand library linking and the multisig hack [duplicate]

Just read about the today issue with parity multisig wallets, https://paritytech.io/blog/security-alert.html where as far I can understand the problem is that a library linked to many wallets was ...
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1answer
254 views

Solidity Library call gives Member not found or not visible after argument-dependent lookup

Using Solidity 0.4.17, I have defined a simple library at ./StringUtils.sol library StringUtils { function isEmptyString(string s) external pure returns (bool) { return (keccak256(s) == ...