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Optimize str::repeat - #48657

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alexcrichton merged 3 commits into
rust-lang:masterfrom
sinkuu:opt_str_repeat
Mar 6, 2018
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Optimize str::repeat#48657
alexcrichton merged 3 commits into
rust-lang:masterfrom
sinkuu:opt_str_repeat

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@sinkuu

@sinkuusinkuu commented Mar 2, 2018

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Improves the performance of str::repeat by bulk copying. Here is the benchmarks of "abcde".repeat(n):

nold [ns/iter]new [ns/iter]diff [%]
127.20527.421+0.794
227.50027.516+0.0581
327.92327.648-0.985
431.20630.145-3.40
535.14431.861-9.34
743.13134.621-19.7
1054.94536.203-34.1
100428.3152.895-87.7

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rust-highfive commented Mar 2, 2018

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r? @dtolnay

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@rust-highfiverust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Mar 2, 2018
hanna-kruppe
hanna-kruppe reviewed Mar 2, 2018
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Comment threadsrc/liballoc/str.rs Outdated

@hanna-kruppehanna-kruppeMar 2, 2018

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Nit: l looks like 1. Better use another letter.

@sanmai-NLsanmai-NLMar 2, 2018

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Better not use single letter identifiers at all...

@CentrilCentril added the T-libs-api [DEPRECATED; DO NOT USE] label Mar 3, 2018
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Centril commented Mar 3, 2018

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Since this introduces new unsafe bits, and introduces non-trivial logic, I think more comments about why this is safe would be good as well as an overall explanation of the logic.

@dtolnay

dtolnay commented Mar 4, 2018

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Nice work! I tried some tests like the following on my computer and see numbers similar to yours.

#[bench]fnrepeat100(b:&mut test::Bencher){
b.iter(|| {S.repeat(100);});}
nold [ns/iter]new [ns/iter]diff [%]
128280
228280
329290
43331−6.1
53734−8.1
74635−24.
105937−37.
10044465−85.

@dtolnay

dtolnay commented Mar 4, 2018

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@bors r+

@bors

bors commented Mar 4, 2018

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📌 Commit 3d58543 has been approved by dtolnay

@borsbors 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 Mar 4, 2018
Manishearth added a commit to Manishearth/rust that referenced this pull request Mar 5, 2018
@Manishearth
Rollup merge ofrust-lang#48657- sinkuu:opt_str_repeat, r=dtolnay
aff626a
Optimize str::repeat
Improves the performance of `str::repeat` by bulk copying. Here is the benchmarks of `"abcde".repeat(n)`:
|`n`|old [ns/iter]|new [ns/iter]|diff [%]|
---|---|---|---
|1|27.205|27.421|+0.794|
|2|27.500|27.516|+0.0581|
|3|27.923|27.648|-0.985|
|4|31.206|30.145|-3.40|
|5|35.144|31.861|-9.34|
|7|43.131|34.621|-19.7|
|10|54.945|36.203|-34.1|
|100|428.31|52.895|-87.7|
@ManishearthManishearth mentioned this pull request Mar 5, 2018
Closed
@kennytmkennytm mentioned this pull request Mar 6, 2018
Merged
kennytm added a commit to kennytm/rust that referenced this pull request Mar 6, 2018
@kennytm
Rollup merge ofrust-lang#48657- sinkuu:opt_str_repeat, r=dtolnay
46d629a
Optimize str::repeat
Improves the performance of `str::repeat` by bulk copying. Here is the benchmarks of `"abcde".repeat(n)`:
|`n`|old [ns/iter]|new [ns/iter]|diff [%]|
---|---|---|---
|1|27.205|27.421|+0.794|
|2|27.500|27.516|+0.0581|
|3|27.923|27.648|-0.985|
|4|31.206|30.145|-3.40|
|5|35.144|31.861|-9.34|
|7|43.131|34.621|-19.7|
|10|54.945|36.203|-34.1|
|100|428.31|52.895|-87.7|
bors added a commit that referenced this pull request Mar 6, 2018
@bors
Auto merge of#48768- kennytm:rollup, r=kennytm
2789b06
Rollup of 14 pull requests
- Successful merges: #48403, #48432, #48546, #48573, #48590, #48657, #48727, #48732, #48753, #48754, #48761, #48474, #48507, #47463
- Failed merges:
@alexcrichton
alexcrichton merged commit 3d58543 into rust-lang:masterMar 6, 2018
@sinkuu
sinkuu deleted the opt_str_repeat branch March 6, 2018 22:14
@scottmcmscottmcm mentioned this pull request Mar 7, 2018
Closed
alexcrichton added a commit to alexcrichton/rust that referenced this pull request Sep 20, 2018
@alexcrichton
std: Check for overflow in str::repeat
4d1d1be
This commit fixes a buffer overflow issue in the standard library
discovered by Scott McMurray where if a large number was passed to
`str::repeat` it may cause and out of bounds write to the buffer of a `Vec`.
This bug was accidentally introduced in rust-lang#48657 when optimizing the
`str::repeat` function. The bug affects stable Rust releases 1.26.0 to
1.29.0. We plan on backporting this fix to create a 1.29.1 release, and
the 1.30.0 release onwards will include this fix.
The fix in this commit is to introduce a deterministic panic in the case of
capacity overflow. When repeating a slice where the resulting length is larger
than the address space, there’s no way it can succeed anyway!
The standard library and surrounding libraries were briefly checked to see if
there were othere instances of preallocating a vector with a calculation that
may overflow. No instances of this bug (out of bounds write due to a calculation
overflow) were found at this time.
Note that this commit is the first steps towards fixing this issue,
we'll be making a formal post to the Rust security list once these
commits have been merged.
alexcrichton added a commit to alexcrichton/rust that referenced this pull request Sep 20, 2018
@alexcrichton
std: Check for overflow in str::repeat
8ac88d3
This commit fixes a buffer overflow issue in the standard library
discovered by Scott McMurray where if a large number was passed to
`str::repeat` it may cause and out of bounds write to the buffer of a `Vec`.
This bug was accidentally introduced in rust-lang#48657 when optimizing the
`str::repeat` function. The bug affects stable Rust releases 1.26.0 to
1.29.0. We plan on backporting this fix to create a 1.29.1 release, and
the 1.30.0 release onwards will include this fix.
The fix in this commit is to introduce a deterministic panic in the case of
capacity overflow. When repeating a slice where the resulting length is larger
than the address space, there’s no way it can succeed anyway!
The standard library and surrounding libraries were briefly checked to see if
there were othere instances of preallocating a vector with a calculation that
may overflow. No instances of this bug (out of bounds write due to a calculation
overflow) were found at this time.
Note that this commit is the first steps towards fixing this issue,
we'll be making a formal post to the Rust security list once these
commits have been merged.
alexcrichton added a commit to alexcrichton/rust that referenced this pull request Sep 20, 2018
@alexcrichton
std: Check for overflow in str::repeat
1b94b84
This commit fixes a buffer overflow issue in the standard library
discovered by Scott McMurray where if a large number was passed to
`str::repeat` it may cause and out of bounds write to the buffer of a `Vec`.
This bug was accidentally introduced in rust-lang#48657 when optimizing the
`str::repeat` function. The bug affects stable Rust releases 1.26.0 to
1.29.0. We plan on backporting this fix to create a 1.29.1 release, and
the 1.30.0 release onwards will include this fix.
The fix in this commit is to introduce a deterministic panic in the case of
capacity overflow. When repeating a slice where the resulting length is larger
than the address space, there’s no way it can succeed anyway!
The standard library and surrounding libraries were briefly checked to see if
there were othere instances of preallocating a vector with a calculation that
may overflow. No instances of this bug (out of bounds write due to a calculation
overflow) were found at this time.
Note that this commit is the first steps towards fixing this issue,
we'll be making a formal post to the Rust security list once these
commits have been merged.
This was referenced Sep 20, 2018
Merged
Merged
Merged
bors added a commit that referenced this pull request Sep 20, 2018
@bors
Auto merge of#54397- alexcrichton:fix-bug-stable, r=steveklabnik
b801ae6
[stable] std: Check for overflow in `str::repeat`
This commit fixes a buffer overflow issue in the standard library
discovered by Scott McMurray where if a large number was passed to
`str::repeat` it may cause and out of bounds write to the buffer of a `Vec`.
This bug was accidentally introduced in #48657 when optimizing the
`str::repeat` function. The bug affects stable Rust releases 1.26.0 to
1.29.0. We plan on backporting this fix to create a 1.29.1 release, and
the 1.30.0 release onwards will include this fix.
The fix in this commit is to introduce a deterministic panic in the case of
capacity overflow. When repeating a slice where the resulting length is larger
than the address space, there’s no way it can succeed anyway!
The standard library and surrounding libraries were briefly checked to see if
there were othere instances of preallocating a vector with a calculation that
may overflow. No instances of this bug (out of bounds write due to a calculation
overflow) were found at this time.
Note that this commit is the first steps towards fixing this issue,
we'll be making a formal post to the Rust security list once these
commits have been merged.
bors added a commit that referenced this pull request Sep 21, 2018
@bors
Auto merge of#54398- alexcrichton:fix-bug-beta, r=steveklabnik
1703b80
[beta] std: Check for overflow in `str::repeat`
This commit fixes a buffer overflow issue in the standard library
discovered by Scott McMurray where if a large number was passed to
`str::repeat` it may cause and out of bounds write to the buffer of a `Vec`.
This bug was accidentally introduced in #48657 when optimizing the
`str::repeat` function. The bug affects stable Rust releases 1.26.0 to
1.29.0. We plan on backporting this fix to create a 1.29.1 release, and
the 1.30.0 release onwards will include this fix.
The fix in this commit is to introduce a deterministic panic in the case of
capacity overflow. When repeating a slice where the resulting length is larger
than the address space, there’s no way it can succeed anyway!
The standard library and surrounding libraries were briefly checked to see if
there were othere instances of preallocating a vector with a calculation that
may overflow. No instances of this bug (out of bounds write due to a calculation
overflow) were found at this time.
Note that this commit is the first steps towards fixing this issue,
we'll be making a formal post to the Rust security list once these
commits have been merged.
bors added a commit that referenced this pull request Sep 21, 2018
@bors
Auto merge of#54399- alexcrichton:fix-bug, r=steveklabnik
1002e40
std: Check for overflow in `str::repeat`
This commit fixes a buffer overflow issue in the standard library
discovered by Scott McMurray where if a large number was passed to
`str::repeat` it may cause and out of bounds write to the buffer of a `Vec`.
This bug was accidentally introduced in #48657 when optimizing the
`str::repeat` function. The bug affects stable Rust releases 1.26.0 to
1.29.0. We plan on backporting this fix to create a 1.29.1 release, and
the 1.30.0 release onwards will include this fix.
The fix in this commit is to introduce a deterministic panic in the case of
capacity overflow. When repeating a slice where the resulting length is larger
than the address space, there’s no way it can succeed anyway!
The standard library and surrounding libraries were briefly checked to see if
there were othere instances of preallocating a vector with a calculation that
may overflow. No instances of this bug (out of bounds write due to a calculation
overflow) were found at this time.
Note that this commit is the first steps towards fixing this issue,
we'll be making a formal post to the Rust security list once these
commits have been merged.
@scottmcmscottmcm mentioned this pull request Sep 21, 2020
Closed
barracuda156 pushed a commit to barracuda156/rust that referenced this pull request Nov 7, 2025
@alexcrichton@barracuda156
std: Check for overflow in str::repeat
eeb5cbe
This commit fixes a buffer overflow issue in the standard library
discovered by Scott McMurray where if a large number was passed to
`str::repeat` it may cause and out of bounds write to the buffer of a `Vec`.
This bug was accidentally introduced in rust-lang#48657 when optimizing the
`str::repeat` function. The bug affects stable Rust releases 1.26.0 to
1.29.0. We plan on backporting this fix to create a 1.29.1 release, and
the 1.30.0 release onwards will include this fix.
The fix in this commit is to introduce a deterministic panic in the case of
capacity overflow. When repeating a slice where the resulting length is larger
than the address space, there’s no way it can succeed anyway!
The standard library and surrounding libraries were briefly checked to see if
there were othere instances of preallocating a vector with a calculation that
may overflow. No instances of this bug (out of bounds write due to a calculation
overflow) were found at this time.
Note that this commit is the first steps towards fixing this issue,
we'll be making a formal post to the Rust security list once these
commits have been merged.
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