Fix a broken link and check internal links (#2195)

In #2153 I aimed to fix a link but broke it.
In this PR, I fix it and add
[`mdbook-linkcheck`](https://github.com/Michael-F-Bryan/mdbook-linkcheck)
to avoid future cases.

Some past fixes that could have been prevented, in addition to mine in
this PR:
* #811
* #2064
* #2146

Note:  
`mdbook-linkcheck` may also check external links with a configuration
change.
It can be beneficial to check also external links from time to time. I
ran it here and found 3 broken links.

Maintainers - sorry for the lack of a preceding issue. We can discuss it
here.
Some remaining work is to fix the outdated internal links in the
translations, not done here.
Let me know what you think about the proposed contribution.

This PR completes #1502.

.github/workflows/build.yml

@@ -147,6 +147,11 @@ jobs:
           MDBOOK_OUTPUT='{"xgettext": {"pot-file": "messages.pot"}}' mdbook build -d po
           msgfmt -o /dev/null --statistics po/messages.pot
 
+      - name: Install mdbook-linkcheck
+        # Opt-in for checking links in translations - add the language below.
+        if: contains(fromJSON('["en", ]'), matrix.language)
+        run: cargo install mdbook-linkcheck --locked --version 0.7.7
+
       - name: Build ${{ matrix.language }} translation
         run: |
           .github/workflows/build.sh ${{ matrix.language }} book/comprehensive-rust-${{ matrix.language }}

README.md

@@ -53,6 +53,10 @@ The course is built using a few tools:
 - [mdbook-exerciser](mdbook-exerciser/)
 - [mdbook-course](mdbook-course/)
 
+In addition,
+[mdbook-linkcheck](https://github.com/Michael-F-Bryan/mdbook-linkcheck) checks
+the internal links.
+
 First install Rust by following the instructions on https://rustup.rs/. Then
 clone this repository:
 
@@ -68,6 +72,7 @@ cargo install mdbook
 cargo install --locked mdbook-svgbob
 cargo install --locked mdbook-i18n-helpers
 cargo install --locked i18n-report
+cargo install --locked mdbook-linkcheck
 cargo install --locked --path mdbook-exerciser
 cargo install --locked --path mdbook-course
 ```

book.toml

@@ -46,7 +46,7 @@ linkcolor = "blue"
 urlcolor = "red"
 
 [output.html]
-curly-quotes = true
+smart-punctuation = true
 additional-js = [
   "theme/speaker-notes.js",
 ]
@@ -278,3 +278,12 @@ use-boolean-and = true
 
 [output.exerciser]
 output-directory = "comprehensive-rust-exercises"
+
+[output.linkcheck]
+optional = true
+follow-web-links = false # change to true to check web links
+exclude = [
+  "comprehensive-rust.pdf",
+  "comprehensive-rust-exercises.zip",
+  # "crates.io", # uncomment when follow-web-links is true
+]

src/android/aidl/types/arrays.md

@@ -13,8 +13,8 @@ signature:
 <details>
 
 - In Android 13 or higher, fixed-size arrays are supported, i.e. `T[N]` becomes
-  `[T; N]`. Fixed-size arrays can have multiple dimensions (e.g. int[3][4]). In
-  the Java backend, fixed-size arrays are represented as array types.
+  `[T; N]`. Fixed-size arrays can have multiple dimensions (e.g. `int[3][4]`).
+  In the Java backend, fixed-size arrays are represented as array types.
 - Arrays in parcelable fields always get translated to `Vec<T>`.
 
 </details>

src/android/interoperability/with-c.md

@@ -19,7 +19,7 @@ fn main() {
 ```
 
 We already saw this in the
-[Safe FFI Wrapper exercise](../../exercises/day-3/safe-ffi-wrapper.md).
+[Safe FFI Wrapper exercise](../../unsafe-rust/exercise.md).
 
 > This assumes full knowledge of the target platform. Not recommended for
 > production.

src/concurrency/async-exercises/dining-philosophers.md

@@ -4,8 +4,8 @@ minutes: 20
 
 # Dining Philosophers --- Async
 
-See [dining philosophers](concurrency/sync-exercises/dining-philosophers.md) for
-a description of the problem.
+See [dining philosophers](../sync-exercises/dining-philosophers.md) for a
+description of the problem.
 
 As before, you will need a local
 [Cargo installation](../../cargo/running-locally.md) for this exercise. Copy the

src/concurrency/shared-state/mutex.md

@@ -6,7 +6,7 @@ minutes: 14
 
 [`Mutex<T>`][1] ensures mutual exclusion _and_ allows mutable access to `T`
 behind a read-only interface (another form of
-[interior mutability](../../borrowing/interior-mutability)):
+[interior mutability](../../borrowing/interior-mutability.md)):
 
 ```rust,editable
 use std::sync::Mutex;

src/glossary.md

@@ -29,16 +29,16 @@ h1#glossary ~ ul > li:first-line {
 <!-- i18n:comment breaks to ensure a nice formatting. -->
 
 - allocate:\
-  Dynamic memory allocation on [the heap](memory-management/stack-vs-heap.md).
+  Dynamic memory allocation on [the heap](memory-management/review.md).
 - argument:\
   Information that is passed into a function or method.
 - Bare-metal Rust:\
   Low-level Rust development, often deployed to a system without an operating
   system. See [Bare-metal Rust](bare-metal.md).
 - block:\
-  See [Blocks](control-flow/blocks.md) and _scope_.
+  See [Blocks](control-flow-basics/blocks-and-scopes.md) and _scope_.
 - borrow:\
-  See [Borrowing](ownership/borrowing.md).
+  See [Borrowing](borrowing/shared.md).
 - borrow checker:\
   The part of the Rust compiler which checks that all borrows are valid.
 - brace:\
@@ -55,7 +55,7 @@ h1#glossary ~ ul > li:first-line {
 - concurrency:\
   The execution of multiple tasks or processes at the same time.
 - Concurrency in Rust:\
-  See [Concurrency in Rust](concurrency.md).
+  See [Concurrency in Rust](concurrency/welcome.md).
 - constant:\
   A value that does not change during the execution of a program.
 - control flow:\
@@ -199,6 +199,6 @@ h1#glossary ~ ul > li:first-line {
   Type that holds no data, written as a tuple with no members.
 - unsafe:\
   The subset of Rust which allows you to trigger _undefined behavior_. See
-  [Unsafe Rust](unsafe.html).
+  [Unsafe Rust](unsafe-rust/unsafe.md).
 - variable:\
   A memory location storing data. Variables are valid in a _scope_.

src/index.md

@@ -38,9 +38,10 @@ Building on this, you're invited to dive into one or more specialized topics:
 - [Bare-metal](bare-metal.md): a whole-day class on using Rust for bare-metal
   (embedded) development. Both microcontrollers and application processors are
   covered.
-- [Concurrency](concurrency.md): a whole-day class on concurrency in Rust. We
-  cover both classical concurrency (preemptively scheduling using threads and
-  mutexes) and async/await concurrency (cooperative multitasking using futures).
+- [Concurrency](concurrency/welcome.md): a whole-day class on concurrency in
+  Rust. We cover both classical concurrency (preemptively scheduling using
+  threads and mutexes) and async/await concurrency (cooperative multitasking
+  using futures).
 
 ## Non-Goals
 

src/other-resources.md

@@ -36,7 +36,7 @@ A small selection of other guides and tutorial for Rust:
 
 - [Learn Rust the Dangerous Way](http://cliffle.com/p/dangerust/): covers Rust
   from the perspective of low-level C programmers.
-- [Rust for Embedded C Programmers](https://docs.opentitan.org/doc/ug/rust_for_c/):
+- [Rust for Embedded C Programmers](https://opentitan.org/book/doc/rust_for_c_devs.html):
   covers Rust from the perspective of developers who write firmware in C.
 - [Rust for professionals](https://overexact.com/rust-for-professionals/):
   covers the syntax of Rust using side-by-side comparisons with other languages

src/running-the-course/course-structure.md

@@ -56,8 +56,8 @@ Everybody will need to install a number of packages as described on the
 
 ### Concurrency in Rust
 
-The [Concurrency in Rust](../concurrency.md) deep dive is a full day class on
-classical as well as `async`/`await` concurrency.
+The [Concurrency in Rust](../concurrency/welcome.md) deep dive is a full day
+class on classical as well as `async`/`await` concurrency.
 
 You will need a fresh crate set up and the dependencies downloaded and ready to
 go. You can then copy/paste the examples into `src/main.rs` to experiment with

src/running-the-course/translations.md

@@ -6,7 +6,7 @@ volunteers:
 - [Brazilian Portuguese][pt-BR] by [@rastringer], [@hugojacob],
   [@joaovicmendes], and [@henrif75].
 - [Chinese (Simplified)][zh-CN] by [@suetfei], [@wnghl], [@anlunx], [@kongy],
-  [@noahdragon], [@superwhd], [@SketchK], and [@nodmp].
+  [@noahdragon], [@superwhd], @SketchK, and [@nodmp].
 - [Chinese (Traditional)][zh-TW] by [@hueich], [@victorhsieh], [@mingyc],
   [@kuanhungchen], and [@johnathan79717].
 - [Japanese][ja] by [@CoinEZ-JPN], [@momotaro1105], [@HidenoriKobayashi] and
@@ -76,7 +76,6 @@ get going. Translations are coordinated on the [issue tracker].
 [@rastringer]: https://github.com/rastringer
 [@reta]: https://github.com/reta
 [@ronaldfw]: https://github.com/ronaldfw
-[@SketchK]: https://github.com/SketchK
 [@suetfei]: https://github.com/suetfei
 [@superwhd]: https://github.com/superwhd
 [@Throvn]: https://github.com/Throvn

src/smart-pointers/rc.md

@@ -24,7 +24,7 @@ fn main() {
   cycles that will get dropped.
 
 [1]: https://doc.rust-lang.org/std/rc/struct.Rc.html
-[2]: ../concurrency/shared_state/arc.md
+[2]: ../concurrency/shared-state/arc.md
 [3]: https://doc.rust-lang.org/std/sync/struct.Mutex.html
 [4]: https://doc.rust-lang.org/std/rc/struct.Weak.html