fix: __del__ not freeing up native resources#38
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acoroleu-tempus wants to merge 4 commits intoextism:mainfrom
Open
fix: __del__ not freeing up native resources#38acoroleu-tempus wants to merge 4 commits intoextism:mainfrom
acoroleu-tempus wants to merge 4 commits intoextism:mainfrom
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When Plugin creates its own CompiledPlugin internally, it should also free it in __del__. Added _owns_compiled_plugin flag to track ownership and avoid freeing externally-passed CompiledPlugin instances. Co-authored-by: Cursor <cursoragent@cursor.com>
Co-authored-by: Cursor <cursoragent@cursor.com>
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@nilslice in case you can take a look, thanks! |
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extism/extism#890
Summary
Fix memory leaks caused by del methods not properly freeing native resources.
Bug 1:
Plugin.__del__never calledextism_plugin_freeThe guard check used hasattr(self, "pointer") but Plugin stores the handle in self.plugin, not self.pointer. This caused the method to
always return early, never freeing the native plugin.
Bug 2: Double-free errors in all
__del__methodsWhen del is called multiple times (e.g., via context manager exit then garbage collection), the code would attempt to free
already-freed resources, causing TypeError or segfaults.
Changes
•
Plugin.__del__: Fix attribute check ("pointer" → "plugin") and add -1 guard•
CompiledPlugin.__del__: Add -1 guard to prevent double-free•
_ExtismFunctionMetadata.__del__: Add None guard and set pointer = None after freeingImpact
This fix enables using extism in long-running services that create fresh plugin instances per request, which previously caused unbounded
memory growth.
Test plan
• Added test_plugin_del_frees_native_resources - verifies Plugin cleanup via context manager
• Added test_compiled_plugin_del_frees_native_resources - verifies CompiledPlugin cleanup
• Added test_extism_function_metadata_del_frees_native_resources - verifies function metadata cleanup
• All tests verify that del can be safely called multiple times