Instruction-Offsets vs Byte-Offsets in dis.dis output NOT A BUG
Please ignore this issue. It was caused by my running the 3.7 library dis in the 3.10 environment.
Bug report
This is new to version 3.10
When 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 >>.
To reproduce, here is an example, I have interspersed the source code with the disassembled output:
try: x = 1
3 4 SETUP_FINALLY 15 (to 21) --- (to 2 * 15 = 30)
6 SETUP_FINALLY 4 (to 12) --- (to 8 + 2 * 4 = 16)
8 LOAD_CONST 1 (1)
10 STORE_NAME 1 (x)
>> 12 POP_BLOCK --- no >>
14 JUMP_FORWARD 6 (to 22) --- (to 16 + 2 * 6 = 28)
except: x = 2
4 16 POP_TOP --- >> (target of 6)
18 POP_TOP
20 POP_TOP
>> 22 LOAD_CONST 2 (2) --- no >>
24 STORE_NAME 1 (x)
26 POP_EXCEPT
>> 28 POP_BLOCK --- >> (target of 14), not >> (target of 48).
finally: x = 3
5 30 LOAD_CONST 3 (3)
32 STORE_NAME 1 (x)
34 JUMP_FORWARD 3 (to 39) --- (to 36 + 2 * 3 = 42)
36 LOAD_CONST 3 (3) --- >> (target of 4)
38 STORE_NAME 1 (x)
40 CONTINUE_LOOP 0
if x == 3:
7 42 LOAD_NAME 1 (x) --- >> (target of 34)
44 LOAD_CONST 3 (3)
46 COMPARE_OP 2 (==)
48 POP_JUMP_IF_FALSE 28 --- (to 28 * 2 = 56)
x = 4
8 50 LOAD_CONST 4 (4)
52 STORE_NAME 1 (x)
54 JUMP_FORWARD 2 (to 58) --- (to 56 + 2 * 2 = 60)
else:
x = 5
10 56 LOAD_CONST 5 (5)
>> 58 STORE_NAME 1 (x) --- no >>
import sys
14 60 LOAD_CONST 6 (0) --- >> (target of 54)
62 LOAD_CONST 7 (None)
64 IMPORT_NAME 2 (sys)
66 STORE_NAME 2 (sys)
Compare with output from 3.9. The compiled bytecodes are slightly different, but the jump addresses and labelled indictors are correct.
In 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.
3 4 SETUP_FINALLY 34 (to 40)
6 SETUP_FINALLY 8 (to 16)
8 LOAD_CONST 1 (1)
10 STORE_NAME 1 (x)
12 POP_BLOCK
14 JUMP_FORWARD 16 (to 32)
4 >> 16 POP_TOP
18 POP_TOP
20 POP_TOP
22 LOAD_CONST 2 (2)
24 STORE_NAME 1 (x)
26 POP_EXCEPT
28 JUMP_FORWARD 2 (to 32)
30 RERAISE
>> 32 POP_BLOCK
5 34 LOAD_CONST 3 (3)
36 STORE_NAME 1 (x)
38 JUMP_FORWARD 6 (to 46)
>> 40 LOAD_CONST 3 (3)
42 STORE_NAME 1 (x)
44 RERAISE
7 >> 46 LOAD_NAME 1 (x)
48 LOAD_CONST 3 (3)
50 COMPARE_OP 2 (==)
52 POP_JUMP_IF_FALSE 60
8 54 LOAD_CONST 4 (4)
56 STORE_NAME 1 (x)
58 JUMP_FORWARD 4 (to 64)
10 >> 60 LOAD_CONST 5 (5)
62 STORE_NAME 1 (x)
14 >> 64 LOAD_CONST 6 (0)
66 LOAD_CONST 7 (None)
68 IMPORT_NAME 2 (sys)
70 STORE_NAME 2 (sys)
Your environment
- 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
- Operating system and architecture: Windows