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diff --git a/docs/miscellaneous.rst b/docs/miscellaneous.rst index c883815c..85fc286c 100644 --- a/docs/miscellaneous.rst +++ b/docs/miscellaneous.rst @@ -145,34 +145,6 @@ Tips and Tricks * If you do **not** want your contracts to receive ether when called via ``send``, you can add a throwing fallback function ``function() { throw; }``. * Initialise storage structs with a single assignment: ``x = MyStruct({a: 1, b: 2});`` -******** -Pitfalls -******** - -Unfortunately, there are some subtleties the compiler does not yet warn you about. - -- In ``for (var i = 0; i < arrayName.length; i++) { ... }``, the type of ``i`` will be ``uint8``, because this is the smallest type that is required to hold the value ``0``. If the array has more than 255 elements, the loop will not terminate. -- If a contract receives Ether (without a function being called), the fallback function is executed. The contract can only rely - on the "gas stipend" (2300 gas) being available to it at that time. This stipend is not enough to access storage in any way. - To be sure that your contract can receive Ether in that way, check the gas requirements of the fallback function. -- If you want to send ether using ``address.send``, there are certain details to be aware of: - - 1. If the recipient is a contract, it causes its fallback function to be executed which can in turn call back into the sending contract - 2. Sending Ether can fail due to the call depth going above 1024. Since the caller is in total control of the call - depth, they can force the transfer to fail, so make sure to always check the return value of ``send``. Better yet, - write your contract using a pattern where the recipient can withdraw Ether instead. - 3. Sending Ether can also fail because the recipient runs out of gas (either explicitly by using ``throw`` or - because the operation is just too expensive). If the return value of ``send`` is checked, this might provide a - means for the recipient to block progress in the sending contract. Again, the best practise here is to use - a "withdraw" pattern instead of a "send" pattern. - -- Loops that do not have a fixed number of iterations, e.g. loops that depends on storage values, have to be used carefully: - Due to the block gas limit, transactions can only consume a certain amount of gas. Either explicitly or just due to - normal operation, the number of iterations in a loop can grow beyond the block gas limit, which can cause the complete - contract to be stalled at a certain point. This does not apply at full extent to ``constant`` functions that are only executed - to read data from the blockchain. Still, such functions may be called by other contracts as part of on-chain operations - and stall those. Please be explicit about such cases in the documentation of your contracts. - ********** Cheatsheet ********** |