cerc-io/solidity
15
0
Fork 0
mirror of https://github.com/ethereum/solidity synced 2023-10-03 13:03:40 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Added Content and Edited for readability

Browse Source 
The example for signextend requested by @bshastry was added. Codeblock was moved before warning for readability.
This commit is contained in:
Vignesh Karthikeyan 2019-06-07 00:47:08 +05:30 committed by GitHub
parent 1978e1d3ff
commit 1d9b6b5bbf
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 11 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
docs/assembly.rst
View File

@ -394,17 +394,6 @@ use ``x_slot``, and to retrieve the byte-offset you use ``x_offset``.
Local Solidity variables are available for assignments, for example:
.. warning::
If you access variables of a type that spans less than 256 bits
(for example ``uint64``, ``address``, ``bytes16`` or ``byte``),
you cannot make any assumptions about bits not part of the
encoding of the type. Especially, do not assume them to be zero.
To be safe, always clear the data properly before you use it
in a context where this is important:
``uint32 x = f(); assembly { x := and(x, 0xffffffff) /* now use x */ }``
To clean signed types, you can use the ``signextend`` opcode:
``assembly { signextend(0, x) }``
.. code::
pragma solidity >=0.4.11 <0.7.0;
@ -418,6 +407,17 @@ Local Solidity variables are available for assignments, for example:
}
}
.. warning::
If you access variables of a type that spans less than 256 bits
(for example ``uint64``, ``address``, ``bytes16`` or ``byte``),
you cannot make any assumptions about bits not part of the
encoding of the type. Especially, do not assume them to be zero.
To be safe, always clear the data properly before you use it
in a context where this is important:
``uint32 x = f(); assembly { x := and(x, 0xffffffff) /* now use x */ }``
To clean signed types, you can use the ``signextend`` opcode:
``assembly { signextend(<bit_width_of_x>, x) }``
Labels
------