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Fix for potentially uninitialized local variable ft used.#2043

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Dead2 merged 1 commit intozlib-ng:developfrom
phprus:functable-init-1
Dec 7, 2025
Merged

Fix for potentially uninitialized local variable ft used.#2043
Dead2 merged 1 commit intozlib-ng:developfrom
phprus:functable-init-1

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@phprus phprus commented Dec 6, 2025

The FUNCTABLE_VERIFY_ASSIGN macro reads values from ft and checks that they are not NULL, but the ft variable is not initialized.

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Fix for potentially uninitialized local variable ft used.
88b8a9d 
Signed-off-by: Vladislav Shchapov <vladislav@shchapov.ru>
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coderabbitai bot commented Dec 6, 2025

Walkthrough

The change adds memory initialization to functable.c by zeroing out a local functable_s instance using memset() before pointer assignments and validations, ensuring all fields start in a known state.

Changes

Cohort / File(s) Summary
Memory Initialization
functable.c		 Initialize local functable_s instance to zero with memset() before subsequent pointer assignments and field validations

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)
Check name Status Explanation
Title check ✅ Passed The title accurately and specifically describes the main change: initializing the uninitialized local variable ft to fix a potential bug.
Description check ✅ Passed The description is directly related to the changeset, explaining the problem that the fix addresses: the uninitialized ft variable issue.
Docstring Coverage ✅ Passed Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
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Reviewing files that changed from the base of the PR and between e2cd66c and 88b8a9d.

📒 Files selected for processing (1)
  • functable.c (1 hunks)
🧰 Additional context used
🧠 Learnings (2)
📓 Common learnings 
Learnt from: KungFuJesus
Repo: zlib-ng/zlib-ng PR: 1802
File: chunkset_tpl.h:135-135
Timestamp: 2024-10-07T21:23:13.401Z
Learning: In the `CHUNKMEMSET` function within `chunkset_tpl.h`, extra bounds checks are avoided to maintain performance in critical code sections. Branching is minimized to prevent negative impacts on speculative execution. The variable `len` is enforced with `safelen` early on.
📚 Learning: 2025-04-15T09:30:10.081Z 
Learnt from: mtl1979
Repo: zlib-ng/zlib-ng PR: 1904
File: arch/riscv/Makefile.in:12-14
Timestamp: 2025-04-15T09:30:10.081Z
Learning: Feature detection modules like riscv_features.c should not be compiled with feature-specific flags (like RVVFLAG) because they need to be compilable on all systems regardless of feature support. These modules perform runtime detection and must initialize feature availability flags to zero on unsupported systems.

Applied to files:

  • functable.c
🧬 Code graph analysis (1)
functable.c (1)
functable.h (1)
  • adler (26-41)
🔇 Additional comments (1)
functable.c (1)

71-76: Correct fix for undefined behavior from uninitialized local variable.

The memset() initialization ensures all fields of the ft struct start in a known state (NULL) before conditional assignments and validation checks. Without this, fields that aren't assigned in any of the compile-time or runtime conditional blocks would contain garbage values, causing undefined behavior when read by the FUNCTABLE_VERIFY_ASSIGN macro at lines 356–368.

The placement is correct—right after variable declarations and before any field assignments—and the size calculation is accurate for the struct. This is essential for correct operation, as the verification checks rely on all fields being either assigned to valid function pointers or remaining NULL to signal initialization failure.

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codecov bot commented Dec 6, 2025 •
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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.32%. Comparing base (e2cd66c) to head (88b8a9d).
⚠️ Report is 5 commits behind head on develop.

Additional details and impacted files 
@@             Coverage Diff             @@
##           develop    #2043      +/-   ##
===========================================
+ Coverage    80.64%   82.32%   +1.68%     
===========================================
  Files          162      162              
  Lines        12883    12923      +40     
  Branches      3174     3174              
===========================================
+ Hits         10389    10639     +250     
+ Misses        1455     1226     -229     
- Partials      1039     1058      +19

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mtl1979
mtl1979 approved these changes Dec 6, 2025
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LGTM

@Dead2 Dead2 merged commit b3ade58 into zlib-ng:develop Dec 7, 2025
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@Dead2 Dead2 mentioned this pull request Jan 30, 2026
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@nmoinvaz nmoinvaz nmoinvaz approved these changes

@Dead2 Dead2 Dead2 approved these changes

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@mtl1979 mtl1979 mtl1979 approved these changes

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