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Improve Initializable readability using intermediate variables #4576

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Sep 5, 2023
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Improve Initializable readability using intermediate variables #4576

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b7de50c
Improve Initializable readability using intermediate variables
Amxx Sep 5, 2023
9249a0b
Update lazy-rice-joke.md
frangio Sep 5, 2023
329dc22
Update contracts/proxy/utils/Initializable.sol
Amxx Sep 5, 2023
175b1e9
Update contracts/proxy/utils/Initializable.sol
Amxx Sep 5, 2023
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5 changes: 5 additions & 0 deletions .changeset/lazy-rice-joke.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
'openzeppelin-solidity': minor
---

`Initializable`: Use intermediate variables to improve readability.
12 changes: 11 additions & 1 deletion contracts/proxy/utils/Initializable.sol
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Expand Up @@ -104,9 +104,19 @@ abstract contract Initializable {
// solhint-disable-next-line var-name-mixedcase
InitializableStorage storage $ = _getInitializableStorage();

// Cache values to avoid duplicated sloads
bool isTopLevelCall = !$._initializing;
uint64 initialized = $._initialized;
if (!(isTopLevelCall && initialized < 1) && !(address(this).code.length == 0 && initialized == 1)) {

// Allowed calls:
// - initialSetup: the contract is not in the initializing state and no previous version was
// initialized
// - construction: the contract is initialized at version 1 (no reininitialization) and the
// current contract is just being deployed
bool initialSetup = initialized == 0 && isTopLevelCall;
bool construction = initialized == 1 && address(this).code.length == 0;

if (!initialSetup && !construction) {
revert AlreadyInitialized();
}
$._initialized = 1;
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$._initialized = 1;
$._initializing = isTopLevelCall;

May be cheaper here, removing redundant SLOAD operation in case of !isTopLevelCall

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@Amxx Amxx Sep 5, 2023 •
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I'm not sure I understand your proposal. Before doing _;, we want to make sure the initializing is true, this would possibly invert it to false.

Also I'm not sure where the duplicated sload is.

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Also I'm not sure where the duplicated sload is.

Since $ is a struct with two fields packed in one storage slot, compiler need to load this slot if you change only one field. If you write all the fields of the structure at once, the compiler does not need to read this slot before SSTORE

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@0xVolosnikov 0xVolosnikov Sep 5, 2023 •
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So it could (in theory) save around 100 gas here

openzeppelin-contracts/contracts/proxy/utils/Initializable.sol

Lines 122 to 125 in 175b1e9

$._initialized = 1;
if (isTopLevelCall) {
$._initializing = true;
}

If do it like

$._initialized = 1;
$._initializing = isTopLevelCall;

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@0xVolosnikov 0xVolosnikov Sep 5, 2023 •
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this would possibly invert it to false

Upd: yes, in this case my proposal should be rather:

  $._initialized = 1;
  $._initializing = true;

And here:

$._initialized = 1;
$._initializing = false;

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Writing it that way requires proving that the _; part doesn't change the value of $._initialized.

I think it is true, because $._initializing = true prevents that value from changing in the rest of the contract, but it's more difficult to see.

I think I prefer to keep the current code at this stage (audit fixes) and come back to this for a future release. @vladyan18 can you open an issue?

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