Fix: add cache free hook and default param free

[haochengxia]

Subsequent PR of #252, aimed at better memory management

• Free the default parameter
• Add cahce_free_hook

[Copilot]

Pull Request Overview

This PR introduces a new hook for releasing plugin resources and enhances parameter cleanup in the plugin-based cache implementation.

• Adds cache_free_hook to the plugin API and invokes it on cache destruction
• Tracks and closes the dynamic library handle for plugins
• Validates and frees previously set plugin_path and cache_name parameters

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
libCacheSim/include/libCacheSim/plugin.h	Defined cache_free_hook_t in the public plugin API
libCacheSim/cache/eviction/plugin_cache.c	Loaded, stored, and called the new free hook; managed dlopen handle; validated/free parameters
example/plugin_v2/plugin_lru.cpp	Implemented cache_free_hook in the LRU plugin example
example/plugin_v2/README.md	Documented the new cache_free_hook in usage section

Comments suppressed due to low confidence (2)

libCacheSim/cache/eviction/plugin_cache.c:220

• There are no existing tests to verify that the free hook is invoked and the plugin handle is closed. Consider adding unit tests that register a dummy plugin and confirm the free hook and dlclose are called.

  if (params->cache_free_hook != NULL) params->cache_free_hook(params->data);

libCacheSim/cache/eviction/plugin_cache.c:417

• Using cache->cache_name in the error message before cache_name is set can lead to a NULL dereference. Consider validating or assigning a default name before reporting errors.

      if (strlen(value) == 0) {

[Copilot]

The result of dlsym for cache_free_hook isn't checked; if the symbol load fails unexpectedly, you may call a garbage pointer. Add a NULL check or error log similar to other hooks.

Suggested change

	cache_free_u.obj = dlsym(handle, "cache_free_hook");
	cache_free_u.obj = dlsym(handle, "cache_free_hook");
	if (cache_free_u.obj == NULL) {
	fprintf(stderr, "Error: Failed to load symbol 'cache_free_hook'.\n");
	return -1; // or appropriate error handling
	}