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Merge remote-tracking branch 'origin/develop' into breaking

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chriseth
2020-11-17 18:51:57 +01:00
parent 6e3f817aac e1292380bd
commit e8a278eefa
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docs/contracts/libraries.rst
+9 -18
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@@ -184,24 +184,15 @@ custom types without the overhead of external function calls:
It is possible to obtain the address of a library by converting
the library type to the ``address`` type, i.e. using ``address(LibraryName)``.
As the compiler cannot know where the library will be
deployed at, these addresses have to be filled into the
final bytecode by a linker
(see :ref:`commandline-compiler` for how to use the
commandline compiler for linking). If the addresses are not
given as arguments to the compiler, the compiled hex code
will contain placeholders of the form ``__Set______`` (where
``Set`` is the name of the library). The address can be filled
manually by replacing all those 40 symbols by the hex
encoding of the address of the library contract.
.. note::
Manually linking libraries on the generated bytecode is discouraged, because
in this way, the library name is restricted to 36 characters.
You should ask the compiler to link the libraries at the time
a contract is compiled by either using
the ``--libraries`` option of ``solc`` or the ``libraries`` key if you use
the standard-JSON interface to the compiler.
As the compiler does not know the address where the library will be deployed, the compiled hex code
will contain placeholders of the form ``__$30bbc0abd4d6364515865950d3e0d10953$__``. The placeholder
is a 34 character prefix of the hex encoding of the keccak256 hash of the fully qualified library
name, which would be for example ``libraries/bigint.sol:BigInt`` if the library was stored in a file
called ``bigint.sol`` in a ``libraries/`` directory. Such bytecode is incomplete and should not be
deployed. Placeholders need to be replaced with actual addresses. You can do that by either passing
them to the compiler when the library is being compiled or by using the linker to update an already
compiled binary. See :ref:`library-linking` for information on how to use the commandline compiler
for linking.
In comparison to contracts, libraries are restricted in the following ways: