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Merge pull request #4844 from ethereum/docs-1644-bytecode

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Clean up metadata and clarify what small changes affect
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chriseth 2018-09-06 18:01:05 +02:00 committed by GitHub
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@ -4,28 +4,28 @@ Contract Metadata
.. index:: metadata, contract verification
The Solidity compiler automatically generates a JSON file, the
contract metadata, that contains information about the current contract.
It can be used to query the compiler version, the sources used, the ABI
and NatSpec documentation in order to more safely interact with the contract
and to verify its source code.
The Solidity compiler automatically generates a JSON file, the contract
metadata, that contains information about the current contract. You can use
this file to query the compiler version, the sources used, the ABI and NatSpec
documentation to more safely interact with the contract and verify its source
code.
The compiler appends a Swarm hash of the metadata file to the end of the
bytecode (for details, see below) of each contract, so that you can retrieve
the file in an authenticated way without having to resort to a centralized
data provider.
Of course, you have to publish the metadata file to Swarm (or some other service)
so that others can access it. The file can be output by using ``solc --metadata``
and the file will be called ``ContractName_meta.json``.
It will contain Swarm references to the source code, so you have to upload
all source files and the metadata file.
You have to publish the metadata file to Swarm (or another service) so that
others can access it. You create the file by using the ``solc --metadata``
command that generates a file called ``ContractName_meta.json``. It contains
Swarm references to the source code, so you have to upload all source files and
the metadata file.
The metadata file has the following format. The example below is presented in a
human-readable way. Properly formatted metadata should use quotes correctly,
reduce whitespace to a minimum and sort the keys of all objects to arrive at a
unique formatting.
Comments are of course also not permitted and used here only for explanatory purposes.
unique formatting. Comments are not permitted and used here only for
explanatory purposes.
.. code-block:: none
@ -96,11 +96,11 @@ Comments are of course also not permitted and used here only for explanatory pur
.. note::
Note the ABI definition above has no fixed order. It can change with compiler versions.
.. note::
Since the bytecode of the resulting contract contains the metadata hash, any change to
the metadata will result in a change of the bytecode. Furthermore, since the metadata
includes a hash of all the sources used, a single whitespace change in any of the source
codes will result in a different metadata, and subsequently a different bytecode.
Since the bytecode of the resulting contract contains the metadata hash, any
change to the metadata results in a change of the bytecode. This includes
changes to a filename or path, and since the metadata includes a hash of all the
sources used, a single whitespace change results in different metadata, and
different bytecode.
Encoding of the Metadata Hash in the Bytecode
=============================================