printf: handle field widths above u16::MAX without panicking

[MadeNavaneeth]

Summary

Fixes #13850

The problem

Rusts write! macro panics with "Formatting argument out of range" when the format width exceeds u16::MAX (65535). GNU printf accepts arbitrarily large field widths, so %65536d, %1000000d, etc. must not panic.

$ printf "%65536d" 5
thread main panicked at num_format.rs:781: Formatting argument out of range

The fix

Replace the write! macro calls in write_output() with manual padding using chunk-based write_spaces/write_zeros helpers — the same approach already used in spec.rs for %s/%c formatting.

Verification

• ✅ 139/139 printf tests pass
• ✅ 5/5 uucore format tests pass
• ✅ cargo clippy -p uucore -- -D warnings clean

[codspeed-hq]

Merging this PR will degrade performance by 5.52%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 1 improved benchmark
❌ 6 regressed benchmarks
✅ 350 untouched benchmarks
🆕 4 new benchmarks
⏩ 50 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	true_consecutive_calls	294.7 ns	350.2 ns	-15.86%
❌	Simulation	split_lines	9.2 ms	10.6 ms	-13.16%
❌	Simulation	split_numeric_suffix	9.7 ms	11.1 ms	-12.55%
❌	Simulation	split_bytes	644.5 µs	675 µs	-4.52%
❌	Simulation	uniq_case_insensitive[10000]	2.8 ms	3 ms	-4.17%
❌	Simulation	uniq_with_count[10000]	3.7 ms	3.8 ms	-3.31%
⚡	Simulation	false_consecutive_calls	350.2 ns	294.7 ns	+18.85%
🆕	Memory	base16_encode_to_dev_null	N/A	22.6 KB	N/A
🆕	Memory	base16_encode_to_file	N/A	22.6 KB	N/A
🆕	Simulation	base16_encode_to_dev_null	N/A	184.3 ms	N/A
🆕	Simulation	base16_encode_to_file	N/A	184.2 ms	N/A

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing MadeNavaneeth:fix/printf-large-field-width (3ee9e26) with main (1a6fb19)²}

Footnotes

1. 50 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on main (7d10e5b) during the generation of this report, so 1a6fb19 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[sylvestre]

it needs a test
thanks

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/cut/bounded-memory (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/tail/retry (passes in this run but fails in the 'main' branch)
Note: The gnu test tests/seq/seq-epipe is now being skipped but was previously passing.