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36 lines
1.3 KiB
ReStructuredText
36 lines
1.3 KiB
ReStructuredText
********************************
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Solidity IR-based Codegen Changes
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********************************
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This section highlights the main differences between the old and the IR-based codegen,
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along with the reasoning behind the changes and how to update affected code.
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Semantic Only Changes
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=====================
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This section lists the changes that are semantic-only, thus potentially
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hiding new and different behavior in existing code.
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* When storage structs are deleted, every storage slot that contains a member of the struct is set to zero entirely. Formally, padding space was left untouched.
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Consequently, if the padding space within a struct is used to store data (e.g. in the context of a contract upgrade), you have to be aware that ``delete`` will now also clear the added member (while it wouldn't have been cleared in the past).
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::
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// SPDX-License-Identifier: GPL-3.0
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pragma solidity >0.7.0;
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contract C {
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struct S {
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uint64 y;
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uint64 z;
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}
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S s;
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function f() public {
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// ...
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delete s;
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// s occupies only first 16 bytes of the 32 bytes slot
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// delete will write zero to the full slot
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}
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}
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We have the same behavior for implicit delete, for example when array of structs is shortened.
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