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Unnecessary SLOADs / MLOADs / CALLDATALOADs in for-each loops #58

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code423n4 opened this issue Nov 16, 2021 · 1 comment
Open

Unnecessary SLOADs / MLOADs / CALLDATALOADs in for-each loops #58

code423n4 opened this issue Nov 16, 2021 · 1 comment
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bug Something isn't working G (Gas Optimization)

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@code423n4
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Handle

pants

Vulnerability details

Vulnerability details

At Zap.sol init function you have the for loop pattern:

for (uint256 i = 0; i < array.length; i++) {
// do something with array[i]
}


In such for loops, the `array.length` is read on every iteration, instead of caching it once in a local variable and read it again using the local variable.

## Impact
Storage reads are much more expensive than reading local variables. Memory and calldata reads are a bit more expensive than reading local variables.

## Tool Used
Manual code review.

## Recommended Mitigation Steps
Read these values from storage / memory / calldata once, cache them in local variables and then read them again using the local variables. For example:

uint256 length = array.length;
for (uint256 i = 0; i < length; i++) {
// do something with array[i]
}


@code423n4 code423n4 added bug Something isn't working G (Gas Optimization) labels Nov 16, 2021
code423n4 added a commit that referenced this issue Nov 16, 2021
@GalloDaSballo
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Agree we should have cached the length value

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Labels
bug Something isn't working G (Gas Optimization)
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