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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Library calls fail depending on compiler version?

I'm trying to deploy my library and call it afterwards with the specific address. While testing this I encountered that the behavior changed over the course of compilers. I tried to follow How to call ...
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When would one want to use a linked library?

My understanding is that if a smart contract consumes a library that only has internal functions, then the compiler will embed the library into the contract bytecode. At the lowest level, there is no ...
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Passing storage of one library to another library

I have two libraries: A and B as well as contract C using them. Library B, in one of its functions, needs to call a couple of functions defined for A.Storage. The code below compiles, tests are ...
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Unit testing a Solidity Library function with a struct memory argument

I am trying to unit test a Solidity Library contract function using truffle and web3. My simplified Library contract looks like this: pragma solidity >=0.5.16; pragma experimental ABIEncoderV2; ...
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1answer
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Can 3rd party call public functions of Solidity library?

A library is deployed separately and a contract is linked to it. All internal library functions are copied to the contract using it. But what about public functions? If the library declares struct ...
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1answer
30 views

How to use solidity library with truffle

I'm using truffle V5.1.13 and when I run truffle test the res variable contains a transaction receipt rather than the expected 2. I notice if I remove everything that has to do with the library things ...
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1answer
71 views

Searching for a value in a dynamic array

I understand that for loops on dynamic arrays are a big no no in Solidity, so I am trying to find an alternative to this problem. Goal: From a dynamic array of numbers, I am trying to extract the ...
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Truffle contract bytecode not updating with library address

After deploying a library using truffle, I want to compile a contract and use the library address inside its generated bytecode. Now inside the contract bytecode I get something like _DateTime______. ...
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Could you add a contract address in place of a library address when editing the bytecode before deplyment?

After compiling a contract that uses a library it is necessary to go into the compile contract bytecode and remove a piece that looks something like "_________library__address______" and replace it ...
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Reference library in external contract

Say contract A {} uses function from library Math {}, can it reference the library from an external contract, and if yes how?
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Function selector computed differently for libraries?

As documented in various places, the function selector is computed as the first four bytes of the keccak256 hash of the function header, which consists of the function name followed by the list of ...
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Any C library available to interact with an Ethereum smart contract?

I need a C library that enables to create, sign transactions and interact with the smart contract.
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1answer
39 views

library modifying string vs string literal

I have a library which has the following function: function strConcat( string memory _a, string memory _b ) internal pure returns (string memory) My contract implements the library ...
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web3 - Can I call a library function without a contract?

I have a library which contains a function concat - it can merge two bytes. I have deployed a contract which uses that library and it works. I would like to make a simple bytes builder on my website. ...
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4answers
340 views

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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1answer
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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
252 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
38 views

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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1answer
39 views

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
79 views

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
71 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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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
122 views

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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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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3answers
260 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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238 views

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
223 views

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
486 views

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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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
160 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
222 views

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
272 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
490 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
188 views

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
189 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
143 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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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
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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
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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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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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385 views

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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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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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 ...