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test: check that sizeof is constant#5139

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test: check that sizeof is constant#5139
vtjnash wants to merge 2 commits into
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vtjnash:jn/sizeof-test

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@vtjnash vtjnash commented May 13, 2026

Create a manual database for CI to make sure that folks cannot accidentally change a struct size on a supported platform. Use ./uv_run_tests sizeof sizeof to regenerate the list. Seemed silly to care a lot about making sure this is correct every release, but not have any tests for it.

@vtjnash vtjnash added the test label May 13, 2026
@vtjnash vtjnash mentioned this pull request May 13, 2026
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@vtjnash @claude
test: check that sizeof is constant
f3872c6 
Create a manual database for CI to make sure that folks cannot
accidentally change a struct size on a supported platform. Use
`./uv_run_tests sizeof sizeof` to regenerate the list.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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vtjnash commented May 13, 2026 •
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Claude also gives us a nice little summary of why some arch are different:

 Linux blocks added:
  - aarch64 (64-bit) — sizes differ from x86_64 only in uv_mutex_t (48 vs 40) and consequently uv_loop_t (856 vs 848), due to glibc's larger pthread_mutex_t on aarch64
  - riscv64 (__riscv && __riscv_xlen == 64) — identical sizes to x86_64
  - arm (32-bit armhf) — differs from i386 in uv_loop_t (472 vs 464), uv_fs_t (296 vs 292), and uv_metrics_t (80 vs 76)

Android blocks added:
An `#if defined(__ANDROID__)` block placed before `#elif defined(__linux__)` (since Android defines both), with four architecture sub-blocks, all measured from the Android NDK r24 / API 24 Bionic libc:

  ┌──────────────┬──────────────────────────────────────────────────────────────────────────────────┐
  │ Architecture │                         Key differences from Linux glibc                         │
  ├──────────────┼──────────────────────────────────────────────────────────────────────────────────┤
  │ x86_64       │ uv_tty_t 288 (vs 312), uv_sem_t 16 (vs 32)                                       │
  ├──────────────┼──────────────────────────────────────────────────────────────────────────────────┤
  │ aarch64      │ Same as Android x86_64; uv_mutex_t 40 (vs 48 on glibc aarch64)                   │
  ├──────────────┼──────────────────────────────────────────────────────────────────────────────────┤
  │ arm (armv7a) │ uv_mutex_t/uv_cond_t/uv_sem_t all 4 bytes (Bionic futex-compact), uv_rwlock_t 40 │
  ├──────────────┼──────────────────────────────────────────────────────────────────────────────────┤
  │ i386         │ Same thread-type compaction as arm; uv_timespec64_t/uv_timeval64_t 12 (vs 16)    │
  └──────────────┴──────────────────────────────────────────────────────────────────────────────────┘

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