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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Instruction-Offsets vs Byte-Offsets in dis.dis output NOT A BUG","articleBody":"**_Please ignore this issue.  It was caused by my running the 3.7 library `dis` in the 3.10 environment._** \r\n\r\n**Bug report**\r\n\r\n**This is new to version 3.10**\r\nWhen disassembling code code block with jumps, bytecode for the jump shows the wrong target instruction number, and/or the bytecode with the wrong address flagged with `\u003e\u003e`.\r\n\r\nTo reproduce, here is an example,  I have interspersed the source code with the disassembled output:\r\n```\r\n\r\n\r\ntry: x = 1\r\n  3           4 SETUP_FINALLY           15 (to 21)  --- (to 2 * 15 = 30)\r\n              6 SETUP_FINALLY            4 (to 12)  --- (to 8 + 2 * 4 = 16)\r\n              8 LOAD_CONST               1 (1)\r\n             10 STORE_NAME               1 (x)\r\n        \u003e\u003e   12 POP_BLOCK                           --- no \u003e\u003e\r\n             14 JUMP_FORWARD             6 (to 22)  --- (to 16 + 2 * 6 = 28)\r\n\r\n except: x = 2\r\n  4          16 POP_TOP                             --- \u003e\u003e (target of 6)\r\n             18 POP_TOP\r\n             20 POP_TOP\r\n        \u003e\u003e   22 LOAD_CONST               2 (2)      --- no \u003e\u003e\r\n             24 STORE_NAME               1 (x)\r\n             26 POP_EXCEPT\r\n        \u003e\u003e   28 POP_BLOCK                           --- \u003e\u003e (target of 14), not \u003e\u003e (target of 48).\r\n\r\nfinally: x = 3\r\n  5          30 LOAD_CONST               3 (3)\r\n             32 STORE_NAME               1 (x)\r\n             34 JUMP_FORWARD             3 (to 39)  --- (to 36 + 2 * 3 = 42)\r\n             36 LOAD_CONST               3 (3)      --- \u003e\u003e (target of 4)\r\n             38 STORE_NAME               1 (x)\r\n             40 CONTINUE_LOOP            0\r\n\r\n\r\nif x == 3:\r\n  7          42 LOAD_NAME                1 (x)      --- \u003e\u003e (target of 34)\r\n             44 LOAD_CONST               3 (3)\r\n             46 COMPARE_OP               2 (==)\r\n             48 POP_JUMP_IF_FALSE       28          --- (to 28 * 2 = 56)\r\n\r\n\tx = 4\r\n  8          50 LOAD_CONST               4 (4)\r\n             52 STORE_NAME               1 (x)\r\n             54 JUMP_FORWARD             2 (to 58)  --- (to 56 + 2 * 2 = 60)\r\n\r\nelse:\r\n \tx = 5\r\n10          56 LOAD_CONST               5 (5)\r\n        \u003e\u003e   58 STORE_NAME               1 (x)      --- no \u003e\u003e\r\n\r\nimport sys\r\n 14          60 LOAD_CONST               6 (0)      --- \u003e\u003e (target of 54)\r\n             62 LOAD_CONST               7 (None)\r\n             64 IMPORT_NAME              2 (sys)\r\n             66 STORE_NAME               2 (sys)\r\n\r\n```\r\n\r\nCompare with output from 3.9.  The compiled bytecodes are slightly different, but the jump addresses and labelled indictors are correct.\r\nIn my opinion, though, the true oparg values (17, etc.), which are shown in 3.10, should be shown instead of the doubled values (34, etc.), which are shown in 3.9.  I would consider this a bug in 3.9.\r\n```\r\n  3           4 SETUP_FINALLY           34 (to 40)\r\n              6 SETUP_FINALLY            8 (to 16)\r\n              8 LOAD_CONST               1 (1)\r\n             10 STORE_NAME               1 (x)\r\n             12 POP_BLOCK\r\n             14 JUMP_FORWARD            16 (to 32)\r\n\r\n  4     \u003e\u003e   16 POP_TOP\r\n             18 POP_TOP\r\n             20 POP_TOP\r\n             22 LOAD_CONST               2 (2)\r\n             24 STORE_NAME               1 (x)\r\n             26 POP_EXCEPT\r\n             28 JUMP_FORWARD             2 (to 32)\r\n             30 RERAISE\r\n        \u003e\u003e   32 POP_BLOCK\r\n\r\n  5          34 LOAD_CONST               3 (3)\r\n             36 STORE_NAME               1 (x)\r\n             38 JUMP_FORWARD             6 (to 46)\r\n        \u003e\u003e   40 LOAD_CONST               3 (3)\r\n             42 STORE_NAME               1 (x)\r\n             44 RERAISE\r\n\r\n  7     \u003e\u003e   46 LOAD_NAME                1 (x)\r\n             48 LOAD_CONST               3 (3)\r\n             50 COMPARE_OP               2 (==)\r\n             52 POP_JUMP_IF_FALSE       60\r\n\r\n  8          54 LOAD_CONST               4 (4)\r\n             56 STORE_NAME               1 (x)\r\n             58 JUMP_FORWARD             4 (to 64)\r\n\r\n 10     \u003e\u003e   60 LOAD_CONST               5 (5)\r\n             62 STORE_NAME               1 (x)\r\n\r\n 14     \u003e\u003e   64 LOAD_CONST               6 (0)\r\n             66 LOAD_CONST               7 (None)\r\n             68 IMPORT_NAME              2 (sys)\r\n             70 STORE_NAME               2 (sys)\r\n```\r\n\r\n**Your environment**\r\n\r\n- CPython versions tested on: Python 3.10.0 (tags/v3.10.0:b494f59, Oct  4 2021, 19:00:18) [MSC v.1929 64 bit (AMD64)] on win32\r\n- Operating system and architecture: Windows\r\n","author":{"url":"https://github.com/mrolle45","@type":"Person","name":"mrolle45"},"datePublished":"2022-05-21T23:07:27.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":11},"url":"https://github.com/93060/cpython/issues/93060"}