robobun 08103aa2ff fix(compile): ensure bytecode alignment accounts for section header (#26299) ...

## Summary

Fixes bytecode alignment in standalone executables to prevent crashes
when loading bytecode cache on Windows.

The bytecode offset needs to be aligned such that when loaded at
runtime, the bytecode pointer is 128-byte aligned. Previously, alignment
was based on arbitrary memory addresses during compilation, which didn't
account for the 8-byte section header prepended at runtime. This caused
the bytecode to be misaligned, leading to segfaults in
`JSC::CachedJSValue::decode` on Windows.

## Root Cause

At runtime, embedded data starts 8 bytes after the PE/Mach-O section
virtual address (which is page-aligned, hence 128-byte aligned). For
bytecode at offset `O` to be aligned:
```
(section_va + 8 + O) % 128 == 0
=> (8 + O) % 128 == 0
=> O % 128 == 120
```

The previous code used `std.mem.alignInSlice()` which found aligned
addresses based on the compilation buffer's arbitrary address, not
accounting for the 8-byte header offset at load time.

## Changes

- **`src/StandaloneModuleGraph.zig`**: Calculate bytecode offset to
satisfy `offset % 128 == 120` instead of using `alignInSlice`
- **`test/regression/issue/26298.test.ts`**: Added regression tests for
bytecode cache in standalone executables

## Test plan

- [x] Added regression test `test/regression/issue/26298.test.ts` with 3
test cases
- [x] Existing `HelloWorldBytecode` test passes
- [x] Build succeeds

Fixes #26298

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Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

2026-01-20 22:42:38 -08:00

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