Improve `NumBufferTrait` associated items by GuillaumeGomez · Pull Request #157976 · rust-lang/rust

GuillaumeGomez · 2026-06-16T15:17:05Z

It allows for NumBuffer::buf size to depend on the integer instead of being the same for all integers.

The idea was suggested by @Amanieu (thanks a lot!).

r? @Amanieu

…ze depends on the integer instead of being the same for all integers

rustbot · 2026-06-16T15:17:09Z

Some changes occurred in integer formatting

cc @tgross35

Amanieu · 2026-06-19T21:35:32Z

@bors r+

rust-bors · 2026-06-19T21:35:35Z

📌 Commit c558f6b has been approved by Amanieu

It is now in the queue for this repository.

Rollup of 3 pull requests Successful merges: - #157976 (Improve `NumBufferTrait` associated items) - #157382 (Suggest `type` next to visibility for const items) - #158157 (Use the direct `From` in `Clone for OnceLock<T>`)

rust-bors · 2026-06-20T00:44:43Z

⌛ Testing commit c558f6b with merge 22398ff...

Workflow: https://github.com/rust-lang/rust/actions/runs/27855057977

@Amanieu

…Amanieu Improve `NumBufferTrait` associated items It allows for `NumBuffer::buf` size to depend on the integer instead of being the same for all integers. The idea was suggested by @Amanieu (thanks a lot!). r? @Amanieu

jhpratt · 2026-06-20T00:46:27Z

yielding to rollup

@bors yield

rust-bors · 2026-06-20T00:46:31Z

Auto build was cancelled. Cancelled workflows:

https://github.com/rust-lang/rust/actions/runs/27855057977

The next pull request likely to be tested is #158162.

Rollup of 3 pull requests Successful merges: - #157976 (Improve `NumBufferTrait` associated items) - #157382 (Suggest `type` next to visibility for const items) - #158157 (Use the direct `From` in `Clone for OnceLock<T>`)

@Amanieu

Rollup merge of #157976 - GuillaumeGomez:numbuffertrait-improvement, r=Amanieu Improve `NumBufferTrait` associated items It allows for `NumBuffer::buf` size to depend on the integer instead of being the same for all integers. The idea was suggested by @Amanieu (thanks a lot!). r? @Amanieu

jhpratt · 2026-06-20T06:09:44Z

@rust-timer build 94ec748

rust-timer · 2026-06-20T07:29:08Z

Finished benchmarking commit (94ec748): comparison URL.

Overall result: ❌ regressions - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	0.4%	[0.2%, 0.8%]	7
Regressions ❌ (secondary)	0.6%	[0.1%, 1.1%]	21
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.4%	[0.2%, 0.8%]	7

Max RSS (memory usage)

Results (primary 2.8%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	2.8%	[2.8%, 2.8%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.8%	[2.8%, 2.8%]	1

Cycles

Results (secondary 3.9%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.9%	[3.1%, 4.6%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 489.308s -> 480.969s (-1.70%)
Artifact size: 390.69 MiB -> 390.68 MiB (-0.00%)

GuillaumeGomez · 2026-06-20T09:54:50Z

I'm surprised: is any of these using NumBuffer? O.o

JonathanBrouwer · 2026-06-21T10:43:45Z

The regression is rustdoc becoming slower in processing these crates, does rustdoc depend on this?

GuillaumeGomez · 2026-06-21T12:42:16Z

rustdoc doesn't use NumBuffer either.

JonathanBrouwer · 2026-06-21T12:50:28Z

It might be doing so indirectly, it seems like NumBuffer is used in the stdlib to format integers in to

GuillaumeGomez · 2026-06-21T12:52:12Z

Nope, nothing is using NumBuffer in the stdlib. ;)

JonathanBrouwer · 2026-06-21T12:53:22Z

@@ -758,7 +758,7 @@ impl u128 {
    /// ```
    #[stable(feature = "int_format_into", since = "CURRENT_RUSTC_VERSION")]
    pub fn format_into(self, buf: &mut NumBuffer<Self>) -> &str {


Well, it's being used here at least, isn't it?

View changes since the review

That's the API added alongside NumBuffer. It's not used anywhere (yet?) in rustc/rustdoc/std.

Ah ok, then I have no clue what's causing this, weird

Welcome to the club. :')

@Amanieu

…r=Amanieu Cleanup `NumBuffer` comment and replace `ilog(10)` with `ilog10()` A [nice person from mastodon](https://toot.cat/@jamey/116815991086205506) pointed out that a `FIXME` comment should have been removed alongside the others in rust-lang#157976, and also pointed out that the documentation mentions that `ilog10` is more optimized than `ilog(10)`. Shouldn't matter much here but since I already made a PR to remove the FIXME comment... r? @Amanieu

@Amanieu

…r=Amanieu Cleanup `NumBuffer` comment and replace `ilog(10)` with `ilog10()` A [nice person from mastodon](https://toot.cat/@jamey/116815991086205506) pointed out that a `FIXME` comment should have been removed alongside the others in rust-lang#157976, and also pointed out that the documentation mentions that `ilog10` is more optimized than `ilog(10)`. Shouldn't matter much here but since I already made a PR to remove the FIXME comment... r? @Amanieu

@Amanieu

Cleanup `NumBuffer` comment and replace `ilog(10)` with `ilog10()` A [nice person from mastodon](https://toot.cat/@jamey/116815991086205506) pointed out that a `FIXME` comment should have been removed alongside the others in rust-lang/rust#157976, and also pointed out that the documentation mentions that `ilog10` is more optimized than `ilog(10)`. Shouldn't matter much here but since I already made a PR to remove the FIXME comment... r? @Amanieu

@Amanieu

Cleanup `NumBuffer` comment and replace `ilog(10)` with `ilog10()` A [nice person from mastodon](https://toot.cat/@jamey/116815991086205506) pointed out that a `FIXME` comment should have been removed alongside the others in rust-lang/rust#157976, and also pointed out that the documentation mentions that `ilog10` is more optimized than `ilog(10)`. Shouldn't matter much here but since I already made a PR to remove the FIXME comment... r? @Amanieu

Improve NumBufferTrait associated items so that NumBuffer::buf si…

c558f6b

…ze depends on the integer instead of being the same for all integers

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jun 16, 2026

rustbot assigned Amanieu Jun 16, 2026

rust-bors Bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 19, 2026

jhpratt mentioned this pull request Jun 20, 2026

Rollup of 3 pull requests #158162

Merged

rust-bors Bot merged commit 45fdd98 into rust-lang:main Jun 20, 2026
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rustbot added this to the 1.98.0 milestone Jun 20, 2026

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rustbot added the perf-regression Performance regression. label Jun 20, 2026

GuillaumeGomez deleted the numbuffertrait-improvement branch June 20, 2026 09:53

JonathanBrouwer reviewed Jun 21, 2026

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GuillaumeGomez mentioned this pull request Jun 26, 2026

Cleanup NumBuffer comment and replace ilog(10) with ilog10() #158448

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rust-timer commented Jun 20, 2026

Overall result: ❌ regressions - please read:

Instruction count

Max RSS (memory usage)

Cycles

Binary size

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