Fix initialization crash for WTinyLFU when parameters are empty #296

AengusMcGuinness · 2026-01-21T20:49:16Z

Description:

This PR fixes an abort error that occurs when WTinyLFU is initialized with an empty parameter string (e.g., using the -e "" flag in the CLI).

The issue was located in cache_init.h, where the code attempted to append default parameters to the user input. When the input was empty, the code produced a malformed string with a leading comma: ",window-size=0.01"

Changes:

Updated the logic in bin/cachesim/cache_init.h to check if eviction_params is NULL or an empty string ("").

If empty, it now passes a clean default string ("window-size=0.01") without a leading comma.

This ensures the initialization sequence is syntactically correct for the internal parser.

Verification:

Command:

(libCacheSim) libCacheSim/_build (libCacheSim) % ./bin/cachesim ../data/cloudPhysicsIO.txt txt tinyLFU 100M -e ""

Before:

[ERROR] 01-21-2026 15:16:29 WTinyLFU.c:376  (tid=8514739968): WTinyLFU does not have parameter ,window-size

After:

[INFO]  01-21-2026 15:28:06 cli_parser.c:559  (tid=8514739968): trace path: ../data/cloudPhysicsIO.txt, trace_type PLAIN_TXT_TRA
CE, ofilepath result/cloudPhysicsIO.txt.cachesim, 12 threads, warmup -1 sec, total 1 algo x 1 size = 1 caches, tinyLFU, eviction
-params:                                                                                                                        
[DEBUG] 01-21-2026 15:28:06 request.h:128  (tid=8514739968): req clock_time 0, id 1, size 1, op nop, valid 1                    
[DEBUG] 01-21-2026 15:28:06 request.h:128  (tid=8514739968): req clock_time 0, id 2, size 1, op nop, valid 1                    
../data/cloudPhysicsIO.txt WTinyLFU-w0.01-SLRU cache size   100MiB,           113872 req, miss ratio 0.4301, throughput 0.21 MQPS ```

gemini-code-assist · 2026-01-21T20:49:29Z

Summary of Changes

Hello @AengusMcGuinness, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a critical initialization crash in the WTinyLFU cache algorithm. Previously, providing an empty string for eviction parameters would lead to a malformed parameter string and an application abort. The changes ensure robust handling of empty or null eviction parameters by supplying a correct default, thereby preventing the crash and allowing the cache to initialize successfully.

Highlights

Fixes WTinyLFU Initialization Crash: Addresses an abort error that occurred when the WTinyLFU cache algorithm was initialized with empty eviction parameters.
Prevents Malformed Parameter String: Corrects an issue where an empty parameter input led to a syntactically incorrect string (e.g., ",window-size=0.01"), causing the initialization to fail.
Ensures Valid Default Parameters: Modifies the initialization logic to explicitly provide "window-size=0.01" as a default parameter when the provided eviction parameters are either NULL or an empty string.

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Code Review

This pull request correctly fixes a crash that occurs when initializing WTinyLFU with empty eviction parameters. The change properly handles both NULL and empty string cases for eviction_params. I have one suggestion to make the code slightly cleaner by using NULL to rely on the default parameters defined within WTinyLFU_init, which improves clarity and maintainability.

gemini-code-assist · 2026-01-21T20:50:37Z

libCacheSim/bin/cachesim/cache_init.h

+    if (eviction_params == NULL || eviction_params[0] == '\0') { 
+      cache = WTinyLFU_init(cc_params, "window-size=0.01");


While this change correctly fixes the crash with empty parameters, passing NULL to WTinyLFU_init would be a cleaner way to apply the default parameters. The WTinyLFU_init function is already designed to use DEFAULT_PARAMS when its cache_specific_params argument is NULL. This approach avoids redundant parsing and makes the intention of using default values more explicit.

if (eviction_params == NULL || eviction_params[0] == '\0') { cache = WTinyLFU_init(cc_params, NULL);

1a1a11a · 2026-01-21T21:40:41Z

Thank you!

1a1a11a · 2026-01-21T22:05:43Z

It looks like there is a failed check

AengusMcGuinness · 2026-01-22T03:19:15Z

thank you for the heads-up! I've pushed a new commit that fixes the trailing whitespace issue in the clang-format check. I also took the suggestion from the code assistant to pass NULL to WTinyLFU_init for a cleaner implementation using internal defaults.

fix(cachesim): prevent malformed tinyLFU params when input is empty

7d9b6f8

AengusMcGuinness requested a review from haochengxia as a code owner January 21, 2026 20:49

gemini-code-assist bot reviewed Jan 21, 2026

View reviewed changes

AengusMcGuinness mentioned this pull request Jan 21, 2026

[BUG]: Robust parameter parsing and error handling #206

Open

style: remove trailing whitespace and use NULL for default params

eaa9d0c

1a1a11a merged commit f249ad3 into 1a1a11a:develop Jan 22, 2026
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Fix initialization crash for WTinyLFU when parameters are empty #296

Fix initialization crash for WTinyLFU when parameters are empty #296

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		if (eviction_params == NULL \|\| eviction_params[0] == '\0') {
		cache = WTinyLFU_init(cc_params, "window-size=0.01");

Fix initialization crash for WTinyLFU when parameters are empty #296

Fix initialization crash for WTinyLFU when parameters are empty #296

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AengusMcGuinness commented Jan 21, 2026

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