Bring the heap_4 improvements to secure_heap

[Moral-Hao]

Description

This includes improvements like addition overflow checks, readability improvements.

Test Steps

Tested locally.

Checklist:

• I have tested my changes. No regression in existing tests.
• I have modified and/or added unit-tests to cover the code changes in this Pull Request.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (bcd6dbd) 94.35% compared to head (c082649) 94.35%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #749   +/-   ##
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  Coverage   94.35%   94.35%           
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  Files           6        6           
  Lines        2443     2443           
  Branches      598      598           
=======================================
  Hits         2305     2305           
  Misses         85       85           
  Partials       53       53           

Flag	Coverage Δ
unittests	94.35% <ø> (ø)

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[ydhuang28]

@Moral-Hao Thank you for the PR. The check for ( xWantedSize & xBlockAllocatedBit ) == 0 is already done by the larger if-statement that contains the if-statement that you've changed. Therefore, these changes are not necessary. I'm closing the PR, but feel free to open a new one if you find a different issue. Thanks!

[Moral-Hao]

@ydhuang28 I don't agree with you. The larger if-statement is checking the original xWantedSize, and variable xWantedSize is changed after that (it will add space for heap structure and for alignment padding).
It is possible that the changed xWantedSize is large enough to make xBlockAllocatedBit being set in xWantedSize. We should check it, and that why I call this PR as check again.

[Moral-Hao]

@aggarg Thank you, your code change is better than mine.