[0.7] [MOD-7297] Replace Variable Length Array on stack with heap allocation

[meiravgri]

(late) backport of #505 to 0.7.
+
add getAlignment() to VecSimIndexAbstract API

[Copilot]

Pull Request Overview

This PR replaces variable length arrays (VLAs) on the stack with heap allocation to improve memory safety and portability. The change removes the use of stack-allocated arrays with dynamic sizes, which are not supported in all C++ standards and can cause stack overflow issues with large data sizes.

• Replaces VLA declarations with allocate_aligned_unique() and allocate_unique() calls
• Introduces new allocator methods that return std::unique_ptr with custom deleters for automatic memory management
• Adds getAlignment() method to the VecSimIndexAbstract API

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/VecSim/vec_sim_tiered_index.h	Replaces stack-allocated VLAs with heap allocation in wrapper methods
src/VecSim/vec_sim_index.h	Replaces stack-allocated VLAs with heap allocation in abstract class wrapper methods
src/VecSim/memory/vecsim_malloc.h	Adds new allocator methods for unique_ptr-based allocation with custom deleter
src/VecSim/memory/vecsim_malloc.cpp	Implements the new allocator methods for unique_ptr-based allocation
src/VecSim/algorithms/hnsw/hnsw_tiered.h	Replaces VLA blob copy with heap allocation in insert job execution
src/VecSim/algorithms/hnsw/hnsw_serializer.h	Replaces VLAs with heap allocation in graph restoration methods
src/VecSim/algorithms/hnsw/hnsw.h	Replaces VLA for element graph data with heap allocation

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[Copilot]

The word 'remalloc' should be 'realloc' to match the standard C library function name.

Suggested change

	// Retrieve the original requested allocation size. Required for remalloc.
	// Retrieve the original requested allocation size. Required for realloc.

[meiravgri]

remalloc is cute

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.70%. Comparing base (c761e6f) to head (5483011).
⚠️ Report is 1 commits behind head on 0.7.

Additional details and impacted files

@@            Coverage Diff             @@
##              0.7     #761      +/-   ##
==========================================
+ Coverage   95.64%   95.70%   +0.06%     
==========================================
  Files          69       69              
  Lines        4221     4238      +17     
==========================================
+ Hits         4037     4056      +19     
+ Misses        184      182       -2     

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