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5
votes
1answer
3k views

How to check the VM trace using Geth?

How to check the VM trace using Geth? I've ran geth with --verbosity 6, and stuff like this gets logged: I0525 01:26:12.418607 core/vm/vm.go:157] running byte VM b82addc7 I0525 01:26:12.419818 core/...
3
votes
1answer
2k views

Creating a function that calls another contract

What is the minimum amount of information you need to know to call a contract from another contract? In this re-entrancy tutorial we see the following source code to "attack" a contract. pragma ...
2
votes
1answer
1k views

New Ethereum Account with Infura

Can I create a new ethereum account using Infura like we do using web3.personal.newAccount();
0
votes
1answer
1k views

“UPDATED : ” “VM Exception while processing transaction: revert”

I tested signature verification of the code presented HERE as follows: running testRPC : root@ubuntu:/home/s# testrpc EthereumJS TestRPC v6.0.3 (ganache-core: 2.0.2) Available Accounts =============...
125
votes
2answers
23k views

`external` vs `public` best practices

Apart from the public modifier Ethereum introduces the external one. Both may be called outside of the contract and inside (the later one by this.f() pattern). Moreover, according to the docs: ...
33
votes
3answers
21k views

ERC20 vs ERC223. List of differences

Is there a list of improvements that we will have in ERC223? Are there examples of contracts? Is there a migration path for existing ERC20 tokens?
39
votes
3answers
15k views

How does the Casper proof of stake algorithm work?

Ethereum plans to move to the Casper proof of stake algorithm in a future version of the network. What are the details of that algorithm, and how does it compare to previous Proof of Stake consensus ...
47
votes
5answers
22k views

Why are selfdestructs used in contract programming?

I'm reading bits and pieces that selfdestructs within contracts are a good thing. Can someone explain what the benefits are of doing a contract selfdestruct when it comes to Ethereum programming? Is ...
20
votes
2answers
3k views

Security review checklist for a smart contract

Is there a tool, checklist of methodology to help reviewing smart contract security? E.g. for each of function you review Is there re-entry possibility and how it behaves on re-entry How it behaves ...
31
votes
8answers
13k views

What are the development tools for Ethereum?

Could someone make a list with development tools for Ethereum together with a short description what they are good for?
27
votes
1answer
10k views

How can I verify a cryptographic signature that was produced by an Ethereum address key pair

If I have a cryptographic signature from an Ethereum address key pair, how can I verify that signature?
34
votes
5answers
18k views

How can I debug a smart contract?

When developing my smart contract, how can I debug it? Are there any debugging, testing tools or simulators that I can use to examine my code?
34
votes
14answers
30k views

How to upgrade solidity compiler in truffle

I couldn't find a way to upgrade a version of truffle solidity compiler. Also curious how to see that information for deployed contracts in truffle console
33
votes
6answers
42k views

How long is the first sync supposed to last?

I've been running Geth (latest version) for around 12 hours and it's still not finished. The command prompt shows this : INFO [05-21|12:05:00] Imported new chain segment blocks=1 txs=...
33
votes
2answers
5k views

Do contracts also have a nonce?

Do contracts also have a nonce and if so how is it calculated? Usual accounts have a nonce that is increased with every transaction. However, contracts can't make transactions, they can only make ...
27
votes
1answer
8k views

Cannot perform write functions in smart contract - invalid address?

I have the following simple smart contract... contract SimpleStorage { uint storedData; function set(uint x) { storedData = x; } function get() constant returns (uint retVal) ...
19
votes
1answer
10k views

At which point the smart contracts get executed?

Let's say I sent a transaction to invoke a smart contract (to its address). At which point will the smart contract get executed? Is it during the transaction validation process? Also, is there any ...
23
votes
1answer
8k views

What is Parity's “warp” sync, and why is it faster than Geth “fast”?

A follow-up of one of the classic questions on this site: One of the answers to this question suggested using Geth's --fast flag to help quickly synchronise the block data. Now, parity comes with ...
21
votes
3answers
5k views

Why does ethereum creates a new block,without even a single transaction? [duplicate]

I'm running a private Ethereum blockchain. When I set one of the nodes to mine, that node continuously creates blocks, even if there are no transactions inside of it. What is the purpose of this?
22
votes
3answers
6k views

How to add new Sealer in Geth 1.6 Proof of Authority?

Hi there Ethereum experts, I'm trying out Proof-of-Authority in Geth 1.6 for my private network and got it to work on a few nodes using Puppeth. Now, I have two questions about maintain the private ...
22
votes
3answers
5k views

Pass a function as a parameter in Solidity

Can you pass a function as a parameter in Solidity? My guess: There is the concept of address in Solidity, but they represent contracts. Contracts can have fallback functions, but I don't think you ...
13
votes
1answer
10k views

geth init, what are the arguments?

this command works but yields a warning of future removal so I'd like to use new option init : ➜ ~ go-ethereum/build/bin/geth --datadir="~/testgeth/" --genesis ~/testgeth/customgenesis.json --port ...
29
votes
5answers
6k views

How to detect if an address is a contract?

I'm interested in knowing whether any particular address is a contract address or a standard address. There have been similar questions on the topic, but I'm not looking to detect whether an address ...
22
votes
4answers
21k views

Solidity: Can you return dynamic arrays in a function?

I know I can return dynamic byte arrays in Solidity, such as in the following code: function createMemoryArray(uint size) returns (bytes) { // Dynamic memory arrays are created using `new`: ...
20
votes
1answer
5k views

What is the exact meaning of a transaction's new receipt 'status' field?

In this answer (https://ethereum.stackexchange.com/a/6010/1529) it seems to say that the status field will always be '1' unless the transaction failed, in which case it will be '0'. In the summary ...
16
votes
2answers
93k views

How fast should be an internet connection to mine ETH?

How fast should be an internet connection to mine ethereum and don't have connection issues? What about ping? And, how many GB of data would get downloaded over a month period? I have a 250GB limit.
16
votes
3answers
11k views

What's the proper way to wait for a transaction to be mined and get the results? [duplicate]

I'm using react to write the frontend for my dApp, and doing this to (attempt to) update react's state via an asynchronous sendTransaction call: var thisJS = this web3.eth.sendTransaction({from: ...
21
votes
1answer
2k views

Are events permanently stored and reliably available to contracts in the future?

I've seen this forum post about using Ethereum as an event store: Events in Solidity, using blockchain as eventstore. However, it doesn't seem conclusive. For instance it says: I confirmed with ...
16
votes
2answers
4k views

What are the key criteria for meeting the ERC20 token standard?

I'm looking for a clear way to describe "the ERC20 token standard" to regular folks like me who are not developers, and can't seem to find a plain language articulation of the core components of that ...
14
votes
2answers
4k views

How can I easily parse a raw transaction?

In the Bitcoin ecosystem, there are tools like https://blockchain.info/decode-tx to decode a raw transaction. Is there a site that offers the equivalent for Ethereum? I'm looking for an easy way to ...
7
votes
1answer
5k views

how to produce enode from node key?

What is the algorithm to produce a bootnode's enode url ? For example, I have this data: Node key: 59233b25bfa4c214a8713e07a395a5d11478de10f36c6c80ba5369541f73bc44 IP: 127.0.0.1 Port: 30303 From ...
26
votes
4answers
5k views

what does `deploy.link` exactly do in `truffle`

Please explain use cases for deploy.link() function in migrations in truffle framework. How would you use it and for what.
16
votes
3answers
4k views

Accessing past values of Smart Contract variables

I would like to know if is possible to inquiry variable values using older blocks. For example I have contract Simple { string32 message public; function Simple() { message = msg....
16
votes
1answer
2k views

How should I handle blockchain forks in my DApp?

In the user interface of my DApp, how can I detect that a blockchain reorganization happened and what should I do to update the UI state once the fork is resolved?
15
votes
3answers
20k views

Call function on another contract

I've created a contract called "Name" which I've deployed to the testnet. this function just register some text for the user and display it back. My contract is: contract Name is mortal{ ...
15
votes
5answers
11k views

Decode input data on transaction

I have an ABI and the input value of the transaction and want to know what function has been called on a contract and with what arguments (one or multiple of different types), preferably using geth, ...
13
votes
2answers
798 views

What is the way to make Ethereum available to users for free?

As the web is mostly free today (I mean the old web, the one < 3), most people won't agree in beeing asked for fuel to run sites, apps, even if the gain in terms of safety and trust are so much ...
13
votes
3answers
19k views

how do you know your db is synced in geth?

In order to answer this question there is a need to get the timestamp of when the database is synced with geth. I can think of two ways of doing that : find the 1st occurrence of 1 block in the geth ...
23
votes
3answers
11k views

Store data in mapping vs. array

I see there're some Solidity examples that are using mapping for storing state, and some are using arrays. For example this example is using mapping: struct Campaign { .... } uint numCampaigns; ...
14
votes
1answer
7k views

How should we set a import path in solidity?

I failed to compile a solidity file with import statement. Error: Source not found: File not found. import './contract.sol'; How should we set a import path? I used web3.js for compiling. ...
13
votes
1answer
2k views

Is it possible to change the block target time?

We're curious to know what factors go into block times in a private network with a limited number of validators. Is this fixed or can it be parameterized in any way? How is it related to block times ...
9
votes
1answer
2k views

Can a contract view the details of a transaction, given a transaction id?

Can a contract view the details of a transaction, given a transaction id? More generally, what details of the blockchain is a given contract aware of?
21
votes
2answers
1k views

What type of operations have negative gas costs?

I understand that some operations cost negative gas because they free up space on the blockchain, such as selfdestructs. What are all the operations that can have negative gas? Does this only occur ...
20
votes
2answers
18k views

How can I return multiple strings from a contract function?

In solidity it's obvious how to get a single string returned from a function. But, I'd like to have the smart contract return multiple string values. Is there a way to do this?
16
votes
2answers
9k views

Is it possible to overflow uints?

The Ethereum token tutorial has a check for a uint256 overflow. function transfer(address _to, uint256 _value) { /* Check if sender has balance and for overflows */ if (balanceOf[msg.sender] ...
13
votes
2answers
4k views

Is it impossible to use an array of strings as the argument to solidity function?

If I try to define a function using an array of strings as an argument, solc gives me the following error: Error: Internal type is not allowed for public or external functions. function test(...
12
votes
3answers
5k views

Are there other Vanity Address generators available?

Are there any Ethereum vanity address generators available other than: Vanityreum (python) Vanieth (go) Which is the fastest? Can they be optimized further? What is the use-case of vanity ...
10
votes
1answer
1k views

Why do some blocks contain no transactions?

While poking through my Geth logs I noticed that block 1,000,006 doesn't actually contain any transactions. Why is that?
9
votes
1answer
3k views

Is there any profit from using pure and view functions modifiers?

I have a function that does not read or modify contract's state: contract C { function add(uint a, uint b) public returns (uint) { uint res = a + b; return res; } } Does it ...
6
votes
2answers
5k views

How to create a token smart contract that sends tokens after recieving payment in ether?

Hey everyone I am launching an ICO. I need to create a smart contract that holds a certain amount of tokens that I created. Then when ether is sent to the smart contract address for my token. It will ...

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