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Better specify the fall function gas cost in the docs. #2945

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chriseth merged 1 commit into from
Sep 21, 2017
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Better specify the fall function gas cost in the docs. #2945

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3 changes: 1 addition & 2 deletions docs/contracts.rst
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Expand Up @@ -519,8 +519,7 @@ Ether (without data). Additionally, in order to receive Ether, the fallback func
must be marked ``payable``. If no such function exists, the contract cannot receive
Ether through regular transactions.

In such a context, there is usually very little gas available to the function call (to be precise, 2300 gas),
so it is important to make fallback functions as cheap as possible.
In such a context, there is usually very little gas available to the function call (to be precise, 2300 gas), so it is important to make fallback functions as cheap as possible. Note that the gas required by a transaction (as opposed to an internal call) that invokes the fallback function is much higher, because each transaction charges an additional amount of 21000 gas or more for things like signature checking.
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@axic axic Sep 21, 2017

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I think this is a bit confusing, it seems like 21000 gas is charged so the contract can do signature checking (which is not the case).

However, that 21000 is not usable by the contract if I am not mistaken?

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@LefterisJP LefterisJP Sep 21, 2017

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It's not usable by the contract, no. I don't think it reads like what you said though. But ofcourse if you think it can be expressed in some more clear way let's change it.


In particular, the following operations will consume more gas than the stipend provided to a fallback function:

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