basicblock_addop Assertion: while-else-loop with try

[15r10nk]

Bug report

Bug description:

while name_5:
    try:
        break
    except:
        pass
else:
    1 if 1 else 1

output (Python 3.12.0rc3+):

python: Python/flowgraph.c:114: basicblock_addop: Assertion `0 <= oparg && oparg < (1 << 30)' failed.

@iritkatriel I think this looks similar to #109627

I tested this bug with faa8003 and the fix does not solve this issue.

CPython versions tested on:

3.12

Operating systems tested on:

Linux

Linked PRs

• gh-109719: Fix missing jump target labels when compiler reorders cold/warm blocks #109734
• [3.12] gh-109719: Fix missing jump target labels when compiler reorders cold/warm blocks (GH-109734) #109749

[sobolevn]

CC @iritkatriel who fixed a similar problem before

[iritkatriel]

Thank you, it's the same bug in another place in the compiler. Keep them coming. How are you doing this? With a fuzzer?

[15r10nk]

Yes, I wrote pysource-codegen which generates random python code.

I am currently adding 3.12 support and find these bugs more or less on the way.
My current setup is here pysource-playground which combines pysource-codegen and pysource-minimize.

[iritkatriel]

That's truly awesome. Thank you.

[gpshead]

connecting some dots here as an FYI - https://github.com/Zac-HD/hypothesmith is another python code generator.

It's be neat to have code generation as you've been doing perhaps setup within our oss-fuzz runs.

[15r10nk]

hi @gpshead, thank you for the connection.
I already know about hypothesmith. I think that both tools have their own strength.

• pysource-codegen is limited to the possible output of ast.unparse but can generate larger source files.
• hypothesmith uses libCST which provides more variation in the generated code, but is limited by the randomness of hypothesis and can not generate larger source files.

oss-fuss is actually new for me. I will look into it. Thank you.