[MOD-9576] Fix memory safety in cosine preprocessing

[meiravgri]

This PR fixes a memory safety issue in our vector preprocessing pipeline, particularly affecting int8_t and uint8_t vectors with cosine similarity.

The Bug

Previously, CosinePreprocessor copied processed_bytes_count bytes from the source blob.
For int8_t / uint8_t + cosine similarity that value is input bytes + 4 (extra norm), so

memcpy(blob, original_blob, processed_bytes_count);

could touch uninitialised memory—undefined behaviour.

Key Changes

Preprocessors API

• Blob‑size propagation – each preprocess* function now receives input_blob_size by reference and can write back the new size after it reallocates or extends the blob.
• Fixed destination size – processed_bytes_count is stored once in the cosine‑preprocessor constructor.
  It is not taken from the preprocess* arguments, so we no longer rely on processed_bytes_count == input_blob_size
• Added assertions to ensure any pre‑allocated storage_blob or query_blob already equals processed_bytes_count, enabling safe in‑place processing; dynamic resizing wasn’t implemented now to avoid added complexity and performance costs—if needed in the future, these checks can be removed and proper allocation logic added.

Factory

• Added processed_bytes_count to PreprocessorsContainerParams.
• Converted CreatePreprocessorsContainerParams from a regular function to a template function to properly handle type-specific size calculations

---

Impact

• Eliminates out‑of‑bounds reads for int8_t / uint8_t cosine vectors.
• API change: downstream code must propagate the (possibly updated) input_blob_size.
• No functional change for other datatype‑metric pairs.
• Negligible perf hit: at most 4 bytes of extra memset.

[codecov]

Codecov Report

Attention: Patch coverage is 89.36170% with 5 lines in your changes missing coverage. Please review.

Project coverage is 96.29%. Comparing base (fbff84f) to head (8967d40).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
.../VecSim/spaces/computer/preprocessor_container.cpp	75.00%	2 Missing ⚠️
src/VecSim/spaces/computer/preprocessors.h	89.47%	2 Missing ⚠️
...rc/VecSim/spaces/computer/preprocessor_container.h	90.90%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #670      +/-   ##
==========================================
+ Coverage   96.24%   96.29%   +0.05%     
==========================================
  Files         112      111       -1     
  Lines        6278     6288      +10     
==========================================
+ Hits         6042     6055      +13     
+ Misses        236      233       -3     

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[meiravgri]

will be covered by svs code

[Copilot]

Pull Request Overview

This PR refactors the preprocessor pipeline API to propagate and fix the blob size across all stages, and it ensures safe in-place processing for cosine similarity by storing the expected processed_bytes_count. It also updates the factory to calculate and pass the new size, and adds a Valgrind build option.

• Switch from a processed_bytes_count value to a size_t &input_blob_size reference throughout all preprocessors.
• Store processed_bytes_count in CosinePreprocessor and add assertions to guard in-place processing.
• Update factories to compute and forward the correct blob size; add USE_VALGRIND option in tests.

Reviewed Changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/unit/test_hnsw_tiered.cpp	Adapted test preprocessor implementations to new input_blob_size API
tests/unit/CMakeLists.txt	Added USE_VALGRIND CMake option
src/VecSim/spaces/computer/preprocessors.h	Changed preprocess interfaces to use size reference; updated CosinePreprocessor
src/VecSim/spaces/computer/preprocessor_container.h	Propagate size reference through container API
src/VecSim/spaces/computer/preprocessor_container.cpp	Updated container implementation to use new size
src/VecSim/index_factories/components/preprocessors_factory.h	Added processed_bytes_count to params
src/VecSim/index_factories/components/components_factory.h	Created templated CreatePreprocessorsContainerParams to compute new size
src/VecSim/CMakeLists.txt	Removed deprecated components_factory.cpp from build
Makefile	Enable USE_VALGRIND flag when requested

Comments suppressed due to low confidence (1)

src/VecSim/spaces/computer/preprocessors.h:61

• The both-null case (when storage_blob and query_blob are both initially nullptr) is never entered because it's inside the if (storage_blob != query_blob) block. You need an else branch matching the original implementation to handle allocating and splitting a single shared nullptr blob.

if (storage_blob != query_blob) {

[Copilot]

You allocate processed_bytes_count bytes but only copy input_blob_size bytes, leaving the extra norm space uninitialized. Consider initializing or writing the norm value explicitly before use to avoid undefined data in the trailing bytes.