Questions tagged [memory]

Questions related to memory use in Solidity or by nodes

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TypeError: Data location must be “storage” or “memory” for parameter in function, but none was given

/// @dev Adds a new transaction to the transaction mapping, if transaction does not exist yet. /// @param destination Transaction target address. /// @param value Transaction ether value. /// @param ...
3
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2answers
4k views

The difference between contract address and wallet address

Disclaimer: this is a rather long question. To my understanding, contract address and wallet address are two profoundly different concepts, with the only thing in common being the fact that they are ...
0
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1answer
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What does this mean: “It is not possible to enumerate storage from within a contract” (Solidity doc)?

In the Solidity docs section on memory, you find this paragraph (emphasis added): Each account has a data area called storage, which is persistent between function calls and transactions. Storage ...
0
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1answer
30 views

member not found or not visible after argument-dependent lookup in mapping

pragma solidity >=0.4.0 <0.7.0; contract New{ mapping(address => string) public users; string name; address[] public userAddress ; //string[] public userNames; ...
0
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1answer
27 views

Expected ')' but got identifier if(string name != users[name]){ ^--^

pragma solidity >=0.4.0 <0.7.0; contract NewHello{ mapping(address => string) public users; // contains a name for every address function updateUser(string memory name) public { ...
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2answers
60 views

Where is the length of an array located in terms of memory layout?

For example, given the following cases: uint[3] memory arr; uint[] memory arr = new uint[](3); Suppose I try to access arr from within an assembly block (using mload, for example). Where (...
1
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0answers
20 views

Calling private function from external - where are referenced type parameters stored in the end?

Let's assume we have something like: contract C { function externalFunction(uint256[] calldata data) external { privateFunction(data); } function privateFunction(uint256[] memory data)...
1
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1answer
77 views

Solidity: Convert from “bytes memory” to “address”

I'm using solidity 0.5.0 and when i try to compile my contract it's giving me this error Explicit type conversion not allowed from "bytes memory" to "address" my code is this: /// @dev get broker ...
2
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1answer
47 views

why a parameter must be “storage” or “memory”?

I am creating a token like this: pragma solidity ^0.5.0; import "../utils/math/SafeMath.sol"; contract ExampleDivisibleNFTs { using SafeMath for uint256; // Percentage of ownership over a ...
1
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1answer
24 views

How do programs on the 'Ethereum World Computer' compare to traditional programs or websites?

So this question has been bugging for me for a while and I can't seem to find the answer to it. Context I have been a web developer for many years. When I access a website, any frontend code is run ...
2
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1answer
280 views

Declaring a memory array of storage pointers in Solidity

I would like to declare a variable as a memory array of pointers to storage arrays of uint256. For example: pragma solidity ^0.4.24; contract A { uint256[] public array0; uint256[] public ...
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0answers
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What is the maximum storage size to store number of addresses in array? [duplicate]

I want to map multiple addresses using one address by doing this: mapping (address => arrayOfAddresses[]) mappingName; What is the maximum size of addresses I can store in that array?
3
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2answers
308 views

convert bytes to uint8[8] using mstore()

I know how to convert bytes to uint8[8] using mload but mstore seemed like it could be more gas efficient. Is something like this possible? function bytesToUintArray(bytes input) returns (uint8[8])) ...
1
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1answer
4k views

GPU'S Failed cannot create DAG

Last night everything is fine and then this morning I check my mining its's closed I think it was restarted or close accidentally then when I open my pool I have this error. ETH: 5 pools are ...
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1answer
2k views

Memory usage and limits for go-ethereum

geth (and swarm) seem to require a lot of memory, and there are also reports that they tend to an all you can eat approach to system limits. 1) What are the actual memory requirements for geth? 2) ...
0
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2answers
34 views

how does Storing and Fetching data works in Smart contracts [closed]

Please help me out with these questions. 1)Where does the contract stores the data? 2)when we access the value of a variable form of a contract, how does it retrieve the latest value? 3)how is the ...
0
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1answer
76 views

error: data location must be storage or memory for parameter in funtion but none was given solidity [duplicate]

pragma solidity ^0.5.0; contract Election{ //model a candidates struct candidate { uint id; string name; uint votecount; } //store candidates //fetch candidate mapping(uint =...
2
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2answers
143 views

How much data can I store in a smart contract, what is the cost and how it is implemented?

If I suppose I use a smart contract as a database, how much data can I store? speaking only of strings and integers, save them in contract data structures does it cost in addition to the gas used for ...
0
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1answer
21 views

Cannot retrieve data from smartcontract during tests

I am writing truffle tests for my smart contract solidity version 0.4.24. The tests are emitting events to write data to memory through smart contract. But I am unable to retrieve data from functions. ...
29
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1answer
15k views

What does the keyword “memory” do exactly?

I've been looking through the code of Etherdice and noticed that some variables are declared like ParserResult memory result; and I haven't found the keyword "memory" in any documentation. What I ...
3
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1answer
91 views

Switching from 'storage' to 'memory' increases the gas-cost

I've read several related answers and blog posts, all of them suggesting that for the sake of reading complex state variables (i.e., arrays and structures), one should always prefer declaring the ...
1
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1answer
568 views

Help with setting up Private POA(Clique) Ethereum Network

Geth Version : 1.8.12-stable-37685930 Testing on Amazon EC2 t2.large(8GB RAM) machine with Ubuntu 16.04 running. I am in need of setting up a multi node private POA(Clique) ethereum network. ...
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2answers
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How could Solidity 0.5.0 dynamic sized parameters be declared as storage?

As I understand it 'memory' in the EVM is a byte array and cannot be dynamically resized, whereas 'storage' is able to be resized. What is happening when a parameter is declared as storage. Where is ...
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0answers
436 views

FATAL ERROR: Rebalance Allocation failed - process out of memory

So while running truffle compile for my contracts on AWS Ubuntu server I got the following error: <--- Last few GCs ---> [17055:0x3985730] 11958 ms: Scavenge 511.7 (553.4) -> 506.9 (553.4) ...
6
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2answers
2k views

How to fill dynamic in-memory array

For some reason solidity doesn't allow to push values into memory array Member "push" is not available in bytes32[] memory outside of storage. Here is sample contract code: pragma solidity ^0.4....
1
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1answer
727 views

Is there a maximum size for arrays in Solidity?

In my solidity code I define 3 arrays with around 700 elements inside. However, when I try to deploy the contract using Geth I am having the following error message: Error: oversized data undefined ...
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0answers
26 views

Why is an address changing when I add it to an array?

I'm encountering a memory / storage issue (I think) w/ an array of addresses where I want to swap out one address with another. Here's how I've initialized the array: address[] public maintainers; ...
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0answers
20 views

How to get live mempool transactions whitout full blokchain

I just want to analyse all mempool txs in realtime. I cant use an api because after several requests my ip gets blocked for some minutes, so I dont get the txs in this time. Thank you for help.
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2answers
73 views

Where are local variables of Primitive (Elementary) data types stored in Solidity

Though in the latest solidity compiler versions, it has been made clear that for reference variables local to a function, one needs to now explicitly mention its location modifier (memory, storage), ...
1
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3answers
211 views

value types(uint, bool, etc) as local variable is set to memory initially?

According to this answer, it says simpler variables like bool, uint, et cetera are not variable in length, and are therefore defaulted to memory, whereas this one mentions uint256 v; is default to ...
0
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1answer
38 views

Finding the memory position of mapping(address => uint) using JavaScript

I am wanting to read data from internal mappings with the following structures: mapping (uint256 => uint256) internal nums; mapping (address => uint256) internal addrToInt; Finding the memory ...
5
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3answers
213 views

Why memory arrays are unresizable?

I don't know the required length of my array before execution of the function.. why technically can't I resize my memory array? What is the common way to go around of this problem, if you are also ...
3
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1answer
77 views

Are balances of all accounts in memory or disk (storage)?

I simulated two contracts that sending balance to another and simply setting value of a variable(var a = 5;). In contrast my expectation, {var a = 5;} contract consumed more gas than the other. In my ...
0
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2answers
117 views

What is the proper pattern to use a temporary variable and ensure it gets stored?

A contract has a state variable, which is complex. For the example, lets say it is a mapping of structs. Inside a method, I want to access that and store the changes. Like so: contract FooManager { ...
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0answers
28 views

getLogs RPC makes filters?

I am stuggling with memory explosion issue of Parity on my EC2 instance. The memory usage of it keeps increasing gradually. I suspect that getLogs API call makes some garbage on the node. But I ...
21
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4answers
7k views

How to store IPFS hash using bytes?

Following Q/A (What datatype should I use for an IPFS address hash?) recommend us to use bytes to store IPFS hash. I was using following example(https://github.com/AdrianClv/ethereum-ipfs/blob/master/...
2
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1answer
222 views

memory keyword in function argument

What does the memory keyword in the argument of a function do? pragma solidity 0.4.24; pragma experimental "ABIEncoderV2"; contract Conditional { struct Condition { address to; bytes4 ...
1
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1answer
235 views

Creating a 2D in-memory array in Solidity

I'm trying to work with 2D in-memory arrays in Solidity, in which the size is not known at compile time. I've noticed that if I define the array size as a constant, then I can use this syntax, which ...
1
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3answers
204 views

Should I use `storage` or `memory` when just reading the value and not changing state?

pragma solidity 0.4.24; contract Test { struct Book { uint id; } Book[] books; uint public status; constructor() public { books.push(Book(10)); } ...
4
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1answer
539 views

Assigning an array creates a pointer or copies an array? (Solidity)

Here is the code: pragma solidity^0.4.16; contract Test { struct SomeData { address[] users; } address[] nullArray; mapping(uint => SomeData) SomeDataList; function ...
0
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0answers
48 views

How to use multidimensional memory array in solidity

I'm working with a project where I have requirement of multidimensional memory array. Here is basic structure of types and person(s) Id -Types -0 -Person1 -Person2 -1 -Person1 -...
1
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1answer
46 views

How can I get the content of storage and memory in my private chain?

I'm looking for some methods to know the content of storage and memory while the contract is running.Mayba some useful tools or abi ? By the way, the abi of geth, debug_writeMemProfile and ...
6
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1answer
304 views

How does dynamic array memory reallocating work?

Let's say I have a dynamic array of some length and I want to push a new element, but memory after last elem is already used. What would happen in such case? Compiler would find a new 'chunk' of ...
6
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2answers
5k views

How to initialize an empty array inside a struct?

Is there a mistake in the way I initialize Bar b in the function foobar? contract Foo { struct Bar { address owner; uint[] x; } Bar[] public bars; function foobar(...
1
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2answers
538 views

Examples to clarify Storage vs Memory assignments / return parameters

Is there a mistake in funcB? I do not understand why/when to mention the variable name of the return parameter in the function signature. contract Foo { // State variables go to Storage uint[...
0
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1answer
95 views

Solidity state variable resets to default inside function

For this project, I am coding smart contracts for Ethereum using Solidity. In the following code, the variable numCertificates should initially be 1. Nonetheless, newCertificateId is 0 when assigned. ...
3
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2answers
161 views

How to pop from (decrease the length of) a memory array in Solidity

I have a function that gets an address array from another contract, conditionally deletes the msg.sender from the array, then saves the new array back to that contract. Because the array backerList ...
1
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1answer
128 views

Compare memory pointers in Solidity

Is there a way to compare pointers in Solidity? I have two local variables: uint256[] memory a = new uint256[](256); uint256[] memory b = a; If I try a == b I get this compiler error: TypeError: ...
2
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1answer
237 views

Always use “memory” for variables created within functions. Bad practice?

Is it bad practice to systematically use the memory keyword for variables declared within a function (other than constructor)?
0
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1answer
233 views

Why do arrays declared within functions reference storage point 0 by default?

According to the Solidity Documentation, for the following code, ". . . the compiler interprets x as a storage pointer and will make it point to the storage slot 0 by default. This has the effect ...