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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Memory leak in `hmac` module with HACL* backend detected by AddressSanitizer","articleBody":"# Bug report\n\n### **Bug Description:**\n\nA memory leak has been detected in the `hmac` module when running `test_hmac`. The issue appears to be specific to the `Hacl_Streaming_HMAC` implementation, as indicated by the stack traces from the AddressSanitizer (ASan) report. The leaks occur within functions responsible for HMAC digest computation (`_Py_LibHacl_Hacl_Streaming_HMAC_digest`, `hmac_digest_compute_locked`), suggesting that memory allocated during these operations is not being properly deallocated.\n\n**Steps to Reproduce:**\n\n1.  Configure the build with the following flags to enable debugging and AddressSanitizer:\n    ```bash\n    CC=clang CXX=clang++ \\\n    ./configure \\\n    --disable-optimizations \\\n    --with-valgrind \\\n    --with-pydebug \\\n    --enable-pystats \\\n    --with-address-sanitizer\n    ```\n\n2.  Build CPython:\n    ```bash\n    make -j$(nproc)\n    ```\n\n3.  Run the `hmac` test suite:\n    ```bash\n    ./python -m test test_hmac\n    ```\n\n**System Information:**\n*   **OS:** `Ubuntu 25.04 (Plucky Puffin)`\n*   **Kernel:** `Linux huawei 6.14.0-33-generic #33-Ubuntu SMP PREEMPT_DYNAMIC Wed Sep 17 23:22:02 UTC 2025 x86_64`\n*   **Clang Version:** `Ubuntu clang version 20.1.2 (0ubuntu1)`\n\n**ASan Leak Report:**\n\n[test.log](https://github.com/user-attachments/files/22907996/test.log)\n\n### CPython versions tested on:\n\nCPython main branch\n\n### Operating systems tested on:\n\nLinux\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-140124\n* gh-140188\n* gh-140192\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/ashm-dev","@type":"Person","name":"ashm-dev"},"datePublished":"2025-10-14T15:25:07.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":6},"url":"https://github.com/140120/cpython/issues/140120"}