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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Pdb crashes after jump with `Fatal Python error: _PyMem_DebugRawFree: bad trailing pad byte`","articleBody":"**Crash report**\r\n\r\nAccess violation occurs when using `pdb` in the following procedure:\r\n1. step in a function\r\n2. step next a few lines inside `print` function\r\n3. before exiting `print` function, jump to the beginning of the code \r\n4. continue\r\n\r\n\u003cdetails\u003e\r\n  \u003csummary\u003eCode Example [test_pdb.py] (click to expand)\u003c/summary\u003e\r\n\r\n```python\r\n__author__ = \"pi\"\r\n__version__ = \"3.14\"\r\n\r\ndef about():\r\n    \"\"\"About\"\"\"\r\n    print(f\"Module: {__file__!r}\",\r\n          f\"Author: {__author__!r}\",\r\n          f\"Version: {__version__!r}\",\r\n          sep='\\n')\r\n\r\nbreakpoint()\r\nabout()\r\n```\r\n\u003c/details\u003e\r\n\r\n**Error messages**\r\n\r\n$ python -Wd -Xdev -Xtracemalloc test_pdb.py\r\n```\r\n\u003e test_pdb.py(12)\u003cmodule\u003e()\r\n-\u003e about()\r\n(Pdb) s\r\n--Call--\r\n\u003e test_pdb.py(4)about()\r\n-\u003e def about():\r\n(Pdb) n\r\n\u003e test_pdb.py(6)about()\r\n-\u003e print(f\"Module: {__file__!r}\",\r\n(Pdb) n\r\n\u003e test_pdb.py(7)about()\r\n-\u003e f\"Author: {__author__!r}\",\r\n(Pdb) j 4\r\n\u003e test_pdb.py(4)about()\r\n-\u003e def about():\r\n(Pdb) c\r\nModule: 'test_pdb.py'\r\nAuthor: 'pi'\r\nVersion: '3.14'\r\nDebug memory block at address p=0000021D17AD8CF0: API 'o'\r\n    432 bytes originally requested\r\n    The 7 pad bytes at p-7 are FORBIDDENBYTE, as expected.\r\n    The 8 pad bytes at tail=0000021D17AD8EA0 are not all FORBIDDENBYTE (0xfd):\r\n        at tail+0: 0x90 *** OUCH\r\n        at tail+1: 0x46 *** OUCH\r\n        at tail+2: 0x05 *** OUCH\r\n        at tail+3: 0x17 *** OUCH\r\n        at tail+4: 0x1d *** OUCH\r\n        at tail+5: 0x02 *** OUCH\r\n        at tail+6: 0x00 *** OUCH\r\n        at tail+7: 0x00 *** OUCH\r\n    Data at p: 00 00 00 00 00 00 00 00 ... f0 b4 b5 16 1d 02 00 00\r\n\r\nMemory block allocated at (most recent call first):\r\n  File \"test_pdb.py\", line 12\r\n\r\nFatal Python error: _PyMem_DebugRawFree: bad trailing pad byte\r\nPython runtime state: finalizing (tstate=0000021D169BEA10)\r\n\r\nCurrent thread 0x000033f0 (most recent call first):\r\n\u003cno Python frame\u003e\r\n```\r\n\r\n**Your environment**\r\n\r\n\u003c!-- Include as many relevant details as possible about the environment you experienced the bug in --\u003e\r\n\r\n- CPython versions tested on: 3.10.4\r\n- Operating system and architecture: Windows10 64bit\r\n\r\n\u003c!--\r\nYou can freely edit this text. Remove any lines you believe are unnecessary.\r\n--\u003e\r\n","author":{"url":"https://github.com/komoto48g","@type":"Person","name":"komoto48g"},"datePublished":"2022-04-20T13:29:18.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":8},"url":"https://github.com/91742/cpython/issues/91742"}