chore: fix C lint errors (issue #6629)

[dipexplorer]

Resolves #6629

Description

What is the purpose of this pull request?

This pull request:

• This PR fixes a C lint error in benchmark.length.c due to the use of VLAs.
  Replaced stack allocation with malloc and free to ensure compatibility with linters and large arrays.

Related Issues

Does this pull request have any related issues?

This pull request:

• resolves Fix C lint errors #6629

Questions

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No.

Other

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No.

Checklist

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• Read, understood, and followed the contributing guidelines.

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[kgryte]

@dipexplorer None of the proposed changes actually addresses the lint error in #6629. You should see how we handle this lint error elsewhere in the codebase by doing a simple grep for the lint rule in question.