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Merge pull request #12910 from ethereum/updatesToGasAndDelegate
Some updates to gas and delegatecall.
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15c2a33eb3
@ -396,26 +396,33 @@ returns that code when executed.
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Gas
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===
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Upon creation, each transaction is charged with a certain amount of **gas**.
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Imposing a cost on transactions serves to secure the network:
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it deincentivizes bad actors from spamming, and pays validators (i.e. miners and stakers)
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for the work that is required to validate new blocks. While the EVM executes the
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Upon creation, each transaction is charged with a certain amount of **gas**
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that has to be paid for by the originator of the transaction (``tx.origin``).
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While the EVM executes the
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transaction, the gas is gradually depleted according to specific rules.
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The **gas price** is a value set by the originator of the transaction, i.e. `tx.origin`, who
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has to pay ``gas_price * gas`` up front from the sending account.
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If some gas is left after execution, it is refunded to the transaction originator.
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If the gas is used up at any point (i.e. it would be negative),
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an out-of-gas exception is triggered, which reverts all modifications
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an out-of-gas exception is triggered, which ends execution and reverts all modifications
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made to the state in the current call frame.
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This mechanism incentivizes economical use of EVM execution time
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and also compensates EVM executors (i.e. miners / stakers) for their work.
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Since each block has a maximum amount of gas, it also limits the amount
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of work needed to validate a block.
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The **gas price** is a value set by the originator of the transaction, who
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has to pay ``gas_price * gas`` up front to the EVM executor.
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If some gas is left after execution, it is refunded to the transaction originator.
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In case of an exception that reverts changes, already used up gas is not refunded.
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Since EVM executors can choose to include a transaction or not,
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transaction senders cannot abuse the system by setting a low gas price.
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.. index:: ! storage, ! memory, ! stack
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Storage, Memory and the Stack
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=============================
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The Ethereum Virtual Machine has three areas where it can store data-
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The Ethereum Virtual Machine has three areas where it can store data:
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storage, memory and the stack.
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Each account has a data area called **storage**, which is persistent between function calls
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@ -504,10 +511,8 @@ Delegatecall / Callcode and Libraries
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There exists a special variant of a message call, named **delegatecall**
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which is identical to a message call apart from the fact that
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the code at the target address is executed in the context of the calling
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contract. In practice this means ``msg.sender`` and ``msg.value`` retain
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the values that were passed to the delegator, while executing code that
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lives in the delegated contract.
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the code at the target address is executed in the context (i.e. at the address) of the calling
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contract and ``msg.sender`` and ``msg.value`` do not change their values.
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This means that a contract can dynamically load code from a different
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address at runtime. Storage, current address and balance still
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