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chriseth
2020-07-13 14:59:22 +02:00
parent fc2e9ec2ff
commit 9b5611dda6
3 changed files with 15 additions and 11 deletions
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docs/assembly.rst
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@@ -132,14 +132,15 @@ For local storage variables or state variables, a single Yul identifier
is not sufficient, since they do not necessarily occupy a single full storage slot.
Therefore, their "address" is composed of a slot and a byte-offset
inside that slot. To retrieve the slot pointed to by the variable ``x``, you
use ``x_slot``, and to retrieve the byte-offset you use ``x_offset``.
use ``x.slot``, and to retrieve the byte-offset you use ``x.offset``.
Using ``x`` itself will result in an error.
Local Solidity variables are available for assignments, for example:
.. code::
// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.4.16 <0.8.0;
pragma solidity >0.6.99 <0.8.0;
contract C {
uint b;
@@ -147,7 +148,7 @@ Local Solidity variables are available for assignments, for example:
assembly {
// We ignore the storage slot offset, we know it is zero
// in this special case.
r := mul(x, sload(b_slot))
r := mul(x, sload(b.slot))
}
}
}
@@ -164,20 +165,21 @@ Local Solidity variables are available for assignments, for example:
``assembly { signextend(<num_bytes_of_x_minus_one>, x) }``
Since Solidity 0.6.0 the name of a inline assembly variable may not end in ``_offset`` or ``_slot``
and it may not shadow any declaration visible in the scope of the inline assembly block
(including variable, contract and function declarations). Similarly, if the name of a declared
variable contains a dot ``.``, the prefix up to the ``.`` may not conflict with any
declaration visible in the scope of the inline assembly block.
Since Solidity 0.6.0 the name of a inline assembly variable may not
shadow any declaration visible in the scope of the inline assembly block
(including variable, contract and function declarations).
Since Solidity 0.7.0, variables and functions declared inside the
inline assembly block may not contain ``.``, but using ``.`` is
valid to access Solidity variables from outside the inline assembly block.
Assignments are possible to assembly-local variables and to function-local
variables. Take care that when you assign to variables that point to
memory or storage, you will only change the pointer and not the data.
You can assign to the ``_slot`` part of a local storage variable pointer.
For these (structs, arrays or mappings), the ``_offset`` part is always zero.
It is not possible to assign to the ``_slot`` or ``_offset`` part of a state variable,
You can assign to the ``.slot`` part of a local storage variable pointer.
For these (structs, arrays or mappings), the ``.offset`` part is always zero.
It is not possible to assign to the ``.slot`` or ``.offset`` part of a state variable,
though.