enhance error codec and exit code - #6602

Reviewing files that changed from the base of the PR and between cd012f9 and 8cf8029.

• crates/vm/src/vm/mod.rs

crates/vm/src/vm/mod.rs (3)

330-340: LGTM! Proper stderr error handler configuration.

The code correctly sets "backslashreplace" as the error handler for stderr (fd == 2), ensuring that unencodable characters are escaped rather than causing encoding errors. This aligns with CPython's default stderr behavior and properly integrates with the TextIOWrapper constructor call.

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881-885: LGTM! Proper use of Python's stderr write method.

Writing through sys.stderr.write() correctly engages the backslashreplace error handler configured at lines 330-335. The use of let _ = to ignore write errors is appropriate here—if stderr itself fails, there's no alternative output mechanism available in this exception handling context.

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862-868: Improved overflow handling for exit codes.

The fallback logic properly handles various integer representations:

• Positive values via to_u32()
• Negative values via to_i32() with cast to preserve two's complement
• Overflow cases default to -1 (represented as 4294967295 in u32)

This prevents panics from the previous unwrap() approach. The overflow default of -1 aligns with observed CPython behavior for very large integers in SystemExit; on POSIX systems, only the low 8 bits are used by shells anyway (making -1 resolve to 255, a semantically reasonable error code).