I'm reading bits and pieces that suicide within contracts are a good thing. Can someone explain what the benefits are of doing a contract suicide when it comes to Ethereum programming? Is there a difference if you're using different clients or implementations, or languages?

  • This question is very unclear. Are you asking about contract suicides, or clients or what? – Tjaden Hess Jan 22 '16 at 4:43
  • Sorry about that - contract. – high110 Jan 22 '16 at 4:46
  • The last sentence is the confusing part, because the go client is a client, solidity is a language, and python could be referring to the python client, or possibly to serpent, the python-like Ethereum language – Tjaden Hess Jan 22 '16 at 4:51
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    tried again - let me know if it's more clear - just trying to see if there are any differences within each implementation? – high110 Jan 22 '16 at 4:57
up vote 37 down vote accepted

Suicides in Ethereum are an operation (an OPCODE actually) at the EVM level, independent of what language or client you are using.

For example, calling suicide(address) sends all of the contract's current balance to address.

This is useful when you are finished with a contract, because it costs far less gas than just sending the balance with address.send(this.balance).

In fact, the SUICIDE opcode uses negative gas because the operation frees up space on the blockchain by clearing all of the contract's data.

This negative gas deducts from the total gas cost of the transaction, so if you're doing some clean-up operations first, SUICIDE can reduce your gas costs.

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    What happens if you try to call suicided contract? Is it state back to zero or does EVM set some flag telling this contract is no longer here? – Mikko Ohtamaa Feb 9 '17 at 20:53
  • What happens if you send ether to the contract which is suicided? – Jossie Calderon Jun 12 '17 at 19:21
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    The balance of the address increases, but since there is no code at the address anymore, the ETH just gets stuck. That ETH is then essentially burned. – Tjaden Hess Jun 12 '17 at 19:23

selfdestruct is the encouraged term and may be found in newer Solidity and Serpent code. It is the same API and behavior, as described in the other answers, and is an alias for suicide.

EIP6 describes the motivation:

The primary reason for us to change the term suicide is to show that people matter more than code and Ethereum is a mature enough of a project to recognize the need for a change. Suicide is a heavy subject and we should make every effort possible to not affect those in our development community who suffer from depression or who have recently lost someone to suicide.

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    selfdestruct alias has been applied to the codebases of Solidity and Serpent and is the preferred term to use. – Hudson Jameson Feb 14 '16 at 6:10

The suicide() function and the relative OPCODE are used when you have a contract that has a bug or an unwanted behaviour and you want to get rid of it.

The suicide(address) is a better version as @tjaden-hess pointed out, when you have a payable contracts (contracts that receive ethers) the ethers will be redirected to address which is a big win.

When you interact with a suicided contract NOTE this: If you send a transaction and/or funds to it then your funds are LOST. Be sure to not send funds or other transactions to it after suiciding a contract.

That's an issue you always have to keep in mind when developing apps that use contracts with a suicide function, be sure the address of the contract is removed from your app after suicide() has been called on the contract, maybe you can always call a getter method to see if the contract responds with a valid value before sending a transaction and/or transferring ethers to it.

The name of the method is now selfdestruct

We have some description of it in the new solidity docs: http://solidity.readthedocs.io/en/v0.4.21/units-and-global-variables.html?highlight=selfdestruct#contract-related

Here's a post from r/ethereum about suicide with more infos and a small discussion about it.

  • This should be the accepted answer. – Jossie Calderon Jun 12 '17 at 19:22

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