[Logic769]

When TMPDIR is set to an empty string, GNU mktemp treats it as
unset and falls back to the system default temporary directory (or to
-p). uutils instead used the empty value as the directory, so
mktemp -t fooXXX created the file in the current directory and even
ignored an explicit -p DIR.

Treat an empty TMPDIR as unset in the template code path, while
keeping the existing precedence where a non-empty TMPDIR wins over
-p when -t is given.

Tests cover -t, --tmpdir, -d -t, and -p DIR -t with an empty
TMPDIR.

Closes #15790

[sylvestre]

@Logic769 again, please stop...
(and it has the ls change here...)

[codspeed]

Merging this PR will improve performance by 7.8%

1 warning, 1 note

⚠️ 123 benchmarks are dominated by system calls

System calls cannot be simulated consistently and are left out of the measure. The reported value understates the real cost. Switch to the Walltime instrument to measure them.

Learn more about system calls

See affected benchmarks

ℹ️ 1 benchmark has no flamegraph

The flamegraph wasn't generated: most of the time was spent in runtime internals, which would leave nothing useful to analyze.

See affected benchmarks

⚡ 1 improved benchmark
✅ 400 untouched benchmarks
⏩ 70 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	CPU Simulation	sort_long_line[10000]	1.1 ms	1 ms	+7.8%

Tip

Curious why performance improved? Comment @codspeedbot explain why performance improved on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing Logic769:mktemp-empty-tmpdir (83583d6) with main (9cc868b)}

Footnotes

1. 70 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. ↩

[sylvestre]

Thanks for your PR