Document unsafety in slice/sort.rs #71568

hbina · 2020-04-26T01:20:16Z

Let me know if these documentations are accurate c:

I don't think I am capable enough to document the safety of partition_blocks, however.

Related issue #66219

rust-highfive · 2020-04-26T01:20:19Z

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @joshtriplett (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

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Muirrum · 2020-06-13T13:51:42Z

@rustbot modify labels to +S-waiting-review -S-waiting-on-author

This is just the reverse of shift_head.

We already implicitly (or explicitly??) do the bound checking for the indexing.

These are simply indexing safety.

joshtriplett · 2020-06-13T20:38:11Z

src/libcore/slice/sort.rs

+    //  1. We are obtaining pointers to references which are guaranteed to be valid.
+    //  2. They cannot overlap because we obtain pointers to difference indices of the slice.
+    //     Namely, `i` and `i-1`.
+    //  3. FIXME: Guarantees that the elements are properly aligned?


If the slice is properly aligned, the elements will be properly aligned. And it's the caller's responsibility to make sure the slice is properly aligned.

joshtriplett · 2020-06-13T20:38:39Z

src/libcore/slice/sort.rs

+    //  1. We are obtaining pointers to references which are guaranteed to be valid.
+    //  2. They cannot overlap because we obtain pointers to difference indices of the slice.
+    //     Namely, `i` and `i+1`.
+    //  3. FIXME: Guarantees that the elements are properly aligned?


Same comment as above.

joshtriplett · 2020-06-13T20:39:20Z

src/libcore/slice/sort.rs

@@ -103,6 +131,8 @@ where
    let mut i = 1;

    for _ in 0..MAX_STEPS {
+        // SAFETY: We already explicitly done the bound checking with `i<len`


Suggested change

// SAFETY: We already explicitly done the bound checking with `i<len`

// SAFETY: We already explicitly did the bound checking with `i<len`

joshtriplett · 2020-06-13T20:40:43Z

src/libcore/slice/sort.rs

@@ -103,6 +131,8 @@ where
    let mut i = 1;

    for _ in 0..MAX_STEPS {
+        // SAFETY: We already explicitly done the bound checking with `i<len`
+        // All our indexing following that is only in the range {0 <= index < len}


Suggested change

// All our indexing following that is only in the range {0 <= index < len}

// All our subsequent indexing is only in the range `0 <= index < len`

joshtriplett · 2020-06-13T20:41:02Z

src/libcore/slice/sort.rs

+    //
+    // a. Indexing:
+    //  1. We checked the size of the array to >=2.
+    //  2. All the indexing that we will do is always between {0 <= index < len-1} at most.


Suggested change

// 2. All the indexing that we will do is always between {0 <= index < len-1} at most.

// 2. All the indexing that we will do is always between `0 <= index < len-1` at most.

joshtriplett · 2020-06-13T20:41:58Z

src/libcore/slice/sort.rs

@@ -404,8 +435,12 @@ where
        // Find the first pair of out-of-order elements.
        let mut l = 0;
        let mut r = v.len();
+
+        // SAFETY: The unsafety below involves indexing an array.
+        // For the first one: we already do the bound checking here with `l<r`.


Suggested change

// For the first one: we already do the bound checking here with `l<r`.

// For the first one: we already do the bounds checking here with `l < r`.

joshtriplett · 2020-06-13T20:42:15Z

src/libcore/slice/sort.rs

+
+        // SAFETY: The unsafety below involves indexing an array.
+        // For the first one: we already do the bound checking here with `l<r`.
+        // For the secondn one: the minimum value for `l` is 0 and the maximum value for `r` is `v.len().`


Suggested change

// For the secondn one: the minimum value for `l` is 0 and the maximum value for `r` is `v.len().`

// For the second one: the minimum value for `l` is 0 and the maximum value for `r` is `v.len().`

joshtriplett · 2020-06-13T20:42:39Z

src/libcore/slice/sort.rs

@@ -452,8 +488,11 @@ where
    let mut l = 0;
    let mut r = v.len();
    loop {
+        // SAFETY: The unsafety below involves indexing an array.
+        // For the first one: we already do the bound checking here with `l<r`.


Suggested change

// For the first one: we already do the bound checking here with `l<r`.

// For the first one: we already do the bounds checking here with `l < r`.

joshtriplett

I posted a few review comments; with those fixed, r=me.

hbina · 2020-06-13T23:03:10Z

Thanks @joshtriplett ! I have applied your requested changes and added some more safety comments. I read through the discussions by more senior people over at #63793
I think some of my documentations might have been too verbose.
Lemme know if they are correct and/or concise enough.

rust-highfive · 2020-06-14T00:43:38Z

The job mingw-check of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

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---
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configure: writing `config.toml` in current directory
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Ensuring the YAML anchors in the GitHub Actions config were expanded
Ensuring the YAML anchors in the GitHub Actions config were expanded
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Build completed successfully in 0:00:22
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Checking rustdoc artifacts (x86_64-unknown-linux-gnu -> i686-pc-windows-gnu)
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---
Done!
some tidy checks failed


command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/tidy" "/checkout/src" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo"


failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test src/tools/tidy
Build completed unsuccessfully in 0:00:27
Build completed unsuccessfully in 0:00:27
== clock drift check ==
  local time: Sat Jun 13 23:21:20 UTC 2020
  network time: Sat, 13 Jun 2020 23:21:20 GMT
== end clock drift check ==

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joshtriplett · 2020-06-16T03:33:32Z

Looks good to me (and definitely not too verbose). However, it looks like the build is failing because you removed ignore-tidy-undocumented-unsafe but there are still some undocumented unsafe blocks. You don't have to document them, but to keep the build passing, can you leave that comment in please?

joshtriplett · 2020-06-16T17:31:40Z

src/libcore/slice/sort.rs

 use crate::cmp;
 use crate::mem::{self, MaybeUninit};
 use crate::ptr;

+// ignore-tidy-undocumented-unsafe


Please don't move this comment below the use lines like this. See the overall diff; these two lines shouldn't change at all.

joshtriplett · 2020-06-19T15:17:31Z

@bors r+ rollup

bors · 2020-06-19T15:17:32Z

📌 Commit 5a9df84 has been approved by joshtriplett

@ghost

…arth Rollup of 13 pull requests Successful merges: - rust-lang#71568 (Document unsafety in slice/sort.rs) - rust-lang#72709 (`#[deny(unsafe_op_in_unsafe_fn)]` in liballoc) - rust-lang#73214 (Add asm!() support for hexagon) - rust-lang#73248 (save_analysis: improve handling of enum struct variant) - rust-lang#73257 (ty: projections in `transparent_newtype_field`) - rust-lang#73261 (Suggest `?Sized` when applicable for ADTs) - rust-lang#73300 (Implement crate-level-only lints checking.) - rust-lang#73334 (Note numeric literals that can never fit in an expected type) - rust-lang#73357 (Use `LocalDefId` for import IDs in trait map) - rust-lang#73364 (asm: Allow multiple template string arguments; interpret them as newline-separated) - rust-lang#73382 (Only display other method receiver candidates if they actually apply) - rust-lang#73465 (Add specialization of `ToString for char`) - rust-lang#73489 (Refactor hir::Place) Failed merges: r? @ghost

rust-highfive assigned joshtriplett Apr 26, 2020

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Apr 26, 2020

hbina changed the title ~~Document unsafety slice sort~~ Document unsafety slice/sort.rs Apr 26, 2020

hbina changed the title ~~Document unsafety slice/sort.rs~~ Document unsafety in slice/sort.rs Apr 29, 2020

JohnCSimon added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels May 10, 2020

rustbot removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Jun 13, 2020

Muirrum added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 13, 2020

hbina added 5 commits June 13, 2020 15:06

Added unsafety documentation to shift_head

7349f2c

Added unsafety documentation to shift_tail

9e8b42c

This is just the reverse of shift_head.

Document unsafety in partial_insertion_sort

9e1e989

We already implicitly (or explicitly??) do the bound checking for the indexing.

Added unsafety documentation with partition and partition equal

c471519

These are simply indexing safety.

Added some unsafety documentation to partition_equal

c710461

joshtriplett reviewed Jun 13, 2020

View reviewed changes

joshtriplett requested changes Jun 13, 2020

View reviewed changes

hbina marked this pull request as ready for review June 13, 2020 23:03

hbina force-pushed the document_unsafety_slice_sort branch from 919aa86 to 31c8674 Compare June 13, 2020 23:03

hbina force-pushed the document_unsafety_slice_sort branch from 31c8674 to 8687dec Compare June 16, 2020 13:24

joshtriplett reviewed Jun 16, 2020

View reviewed changes

Added some more documentations to unsafety blocks in slice/sort.rs

5a9df84

hbina force-pushed the document_unsafety_slice_sort branch from 8687dec to 5a9df84 Compare June 16, 2020 20:20

bors 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, 2020

Manishearth mentioned this pull request Jun 19, 2020

Rollup of 13 pull requests #73511

Merged

bors merged commit 85e1c3b into rust-lang:master Jun 20, 2020

LeSeulArtichaut mentioned this pull request Jun 20, 2020

Document all unsafety used in libcore and libstd #66219

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hbina deleted the document_unsafety_slice_sort branch June 21, 2020 04:53

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Document unsafety in slice/sort.rs #71568

Document unsafety in slice/sort.rs #71568

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bors commented Jun 19, 2020

	// SAFETY: We already explicitly done the bound checking with `i<len`
	// SAFETY: We already explicitly did the bound checking with `i<len`

	// All our indexing following that is only in the range {0 <= index < len}
	// All our subsequent indexing is only in the range `0 <= index < len`

	// 2. All the indexing that we will do is always between {0 <= index < len-1} at most.
	// 2. All the indexing that we will do is always between `0 <= index < len-1` at most.

	// For the first one: we already do the bound checking here with `l<r`.
	// For the first one: we already do the bounds checking here with `l < r`.

	// For the secondn one: the minimum value for `l` is 0 and the maximum value for `r` is `v.len().`
	// For the second one: the minimum value for `l` is 0 and the maximum value for `r` is `v.len().`

Document unsafety in slice/sort.rs #71568

Document unsafety in slice/sort.rs #71568

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