10 bugs found

Hi Claude Team!

Seeing an agent build a compiler from scratch is amazing. We got curious about how it handles edge cases, so we evaluate with a tool we built, [issuemut](https://arxiv.org/abs/2510.07834).

After a 12-hour run, we found 10 unique bugs. We actually used Claude Code to help us triage and organize them into this repo: https://github.com/bi6c/ccc-bug-reports.

It would be incredible to see if Claude Code can close the loop and fix the bugs itself based on this feedback.

The claude c compiler is built based on the Commit: `6f1b99ac`.

## Bug Summary

### Panics (Internal Compiler Errors)

| # | Directory | Panic Location | Error Message | Instances |
|---|---|---|---|---|
| 1 | `001-i128-to-float-f128` | `i128_ops.rs:164` | unsupported i128-to-float conversion: F128 | 718 |
| 2 | `002-global-init-oob` | `global_init_bytes.rs:1289` | index out of bounds: the len is 8 but the index is 8 | 354 |
| 3 | `003-float-to-i128-f128` | `i128_ops.rs:187` | unsupported float-to-i128 conversion: F128 | 349 |
| 4 | `004-float-binop-ashr` | `traits.rs:347` | unsupported float binop: AShr on type F128 | 96 |
| 5 | `005-compound-struct-oob` | `global_init_compound_struct.rs:492` | range start index 24 out of range for slice of length 16 | 8 |

### Timeouts (Compiler Hangs)

| # | Directory | Phase | Description | Seed Timeouts | Mutation Timeouts |
|---|---|---|---|---|---|
| 6 | `006-ucn-macro-param-hang` | Preprocessor | UCN/UTF-8 in macro parameter causes infinite loop | 6 seeds | 2,206 |
| 7 | `007-large-init-array-hang` | IR Lowering | Large initialized local array (>= 1MB) causes hang | 2 seeds | ~1,775 |
| 8 | `008-huge-designator-hang` | IR Lowering | Huge designated initializer index causes hang | 2 seeds | ~1,775 |
| 9 | `009-long-double-huge-exponent-hang` | Sema | `long double` literal with exponent >= 10^6 hangs | 1 seed | 367 |
| 10 | `010-zero-size-struct-range-init-hang` | Sema | Range designator + compound literal on empty struct | 0 seeds | mutation-only |