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Update documentation.

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chriseth 2021-11-02 12:04:31 +01:00
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11
docs/control-structures.rst
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@ -114,10 +114,19 @@ otherwise, the ``value`` option would not be available.
Due to the fact that the EVM considers a call to a non-existing contract to
always succeed, Solidity uses the ``extcodesize`` opcode to check that
the contract that is about to be called actually exists (it contains code)
and causes an exception if it does not.
and causes an exception if it does not. This check is skipped if the return
data will be decoded after the call and thus the ABI decoder will catch the
case of a non-existing contract.
Note that this check is not performed in case of :ref:`low-level calls <address_related>` which
operate on addresses rather than contract instances.
.. note::
Be careful when using high-level calls to
:ref:`precompiled contracts <precompiledContracts>`,
since the compiler considers them non-existing according to the
above logic even though they execute code and can return data.
Function calls also cause exceptions if the called contract itself
throws an exception or goes out of gas.

21
docs/introduction-to-smart-contracts.rst
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@ -565,3 +565,24 @@ contracts, the Ether is forever lost.
If you want to deactivate your contracts, you should instead **disable** them
by changing some internal state which causes all functions to revert. This
makes it impossible to use the contract, as it returns Ether immediately.
.. index:: ! precompiled contracts, ! precompiles, ! contract;precompiled
.. _precompiledContracts:
Precompiled Contracts
=====================
There is a small set of contract addresses that are special:
The address range between ``1`` and (including) ``8`` contains
"precompiled contracts" that can be called as any other contract
but their behaviour (and their gas consumption) is not defined
by EVM code stored at that address (they do not contain code)
but instead is implemented in the EVM execution environment itself.
Different EVM-compatible chains might use a different set of
precompiled contracts. It might also be possible that new
precompiled contracts are added to the Ethereum main chain in the future,
but you can reasonabyly expect them to always be in the range between
``1`` and ``0xffff`` (inclusive).