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An array's length should be cached to save gas in for-loops #288

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code423n4 opened this issue Dec 19, 2021 · 1 comment
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An array's length should be cached to save gas in for-loops #288

code423n4 opened this issue Dec 19, 2021 · 1 comment
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bug Something isn't working duplicate This issue or pull request already exists G (Gas Optimization) sponsor confirmed Sponsor agrees this is a problem and intends to fix it (OK to use w/ "disagree with severity")

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@code423n4
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Dravee

Vulnerability details

Impact

Increased gas cost

Proof of Concept

(As seen on this contest: code-423n4/2021-10-slingshot-findings#63)
Reading array length at each iteration of the loop takes 6 gas (3 for mload and 3 to place memory_offset) in the stack.

Caching the array length in the stack saves around 3 gas per iteration.

Instances include:

Tools Used

VS Code

Recommended Mitigation Steps

Store the array's length in a variable before the for-loop, and use it instead.
@code423n4 code423n4 added bug Something isn't working G (Gas Optimization) labels Dec 19, 2021
code423n4 added a commit that referenced this issue Dec 19, 2021
@code423n4
Dravee issue #288
93c19c1
@loki-sama loki-sama added the sponsor confirmed Sponsor agrees this is a problem and intends to fix it (OK to use w/ "disagree with severity") label Dec 30, 2021
@loki-sama loki-sama mentioned this issue Jan 11, 2022
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@0xleastwood
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Duplicate of #249

@0xleastwood 0xleastwood marked this as a duplicate of #249 Jan 23, 2022
@0xleastwood 0xleastwood added the duplicate This issue or pull request already exists label Jan 24, 2022
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bug Something isn't working duplicate This issue or pull request already exists G (Gas Optimization) sponsor confirmed Sponsor agrees this is a problem and intends to fix it (OK to use w/ "disagree with severity")
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@loki-sama @0xleastwood @code423n4