Auto merge of #34358 - Manishearth:rollup, r=Manishearth

Rollup of 4 pull requests

- Successful merges: #34313, #34335, #34340, #34356
- Failed merges:

Author: bors

src/doc/book/compiler-plugins.md

@@ -34,7 +34,7 @@ code that manipulates syntax trees at
 compile time.
 
 Let's write a plugin
-[`roman_numerals.rs`](https://github.com/rust-lang/rust/tree/master/src/test/auxiliary/roman_numerals.rs)
+[`roman_numerals.rs`](https://github.com/rust-lang/rust/blob/master/src/test/run-pass-fulldeps/auxiliary/roman_numerals.rs)
 that implements Roman numeral integer literals.
 
 ```rust,ignore
@@ -166,7 +166,8 @@ quasiquote as an ordinary plugin library.
 
 Plugins can extend [Rust's lint
 infrastructure](../reference.html#lint-check-attributes) with additional checks for
-code style, safety, etc. Now let's write a plugin [`lint_plugin_test.rs`](https://github.com/rust-lang/rust/blob/master/src/test/auxiliary/lint_plugin_test.rs)
+code style, safety, etc. Now let's write a plugin
+[`lint_plugin_test.rs`](https://github.com/rust-lang/rust/blob/master/src/test/run-pass-fulldeps/auxiliary/lint_plugin_test.rs)
 that warns about any item named `lintme`.
 
 ```rust,ignore

src/doc/rustc-ux-guidelines.md

@@ -56,7 +56,19 @@ Error explanations are long form descriptions of error messages provided with
 the compiler. They are accessible via the `--explain` flag. Each explanation
 comes with an example of how to trigger it and advice on how to fix it.
 
-* All of them are accessible [online](https://github.com/rust-lang/rust/blob/master/src/librustc/diagnostics.rs).
+* All of them are accessible [online](http://doc.rust-lang.org/error-index.html),
+  which are auto-generated from rustc source code in different places:
+  [librustc](https://github.com/rust-lang/rust/blob/master/src/librustc/diagnostics.rs),
+  [librustc_borrowck](https://github.com/rust-lang/rust/blob/master/src/librustc_borrowck/diagnostics.rs),
+  [librustc_const_eval](https://github.com/rust-lang/rust/blob/master/src/librustc_const_eval/diagnostics.rs),
+  [librustc_lint](https://github.com/rust-lang/rust/blob/master/src/librustc_lint/types.rs),
+  [librustc_metadata](https://github.com/rust-lang/rust/blob/master/src/librustc_metadata/diagnostics.rs),
+  [librustc_mir](https://github.com/rust-lang/rust/blob/master/src/librustc_mir/diagnostics.rs),
+  [librustc_passes](https://github.com/rust-lang/rust/blob/master/src/librustc_passes/diagnostics.rs),
+  [librustc_privacy](https://github.com/rust-lang/rust/blob/master/src/librustc_privacy/diagnostics.rs),
+  [librustc_resolve](https://github.com/rust-lang/rust/blob/master/src/librustc_resolve/diagnostics.rs),
+  [librustc_trans](https://github.com/rust-lang/rust/blob/master/src/librustc_trans/diagnostics.rs),
+  [librustc_typeck](https://github.com/rust-lang/rust/blob/master/src/librustc_typeck/diagnostics.rs).
 * Explanations have full markdown support. Use it, especially to highlight
 code with backticks.
 * When talking about the compiler, call it `the compiler`, not `Rust` or

src/libcore/ops.rs

@@ -1608,6 +1608,7 @@ impl<Idx: PartialOrd<Idx>> RangeFrom<Idx> {
 /// See the [`contains()`](#method.contains) method for its characterization.
 ///
 /// It cannot serve as an iterator because it doesn't have a starting point.
+///
 /// ```
 /// fn main() {
 ///     assert_eq!((..5), std::ops::RangeTo{ end: 5 });

src/libstd/ffi/c_str.rs

@@ -509,6 +509,38 @@ impl CStr {
     /// The returned pointer will be valid for as long as `self` is and points
     /// to a contiguous region of memory terminated with a 0 byte to represent
     /// the end of the string.
+    ///
+    /// **WARNING**
+    ///
+    /// It is your responsibility to make sure that the underlying memory is not
+    /// freed too early. For example, the following code will cause undefined
+    /// behaviour when `ptr` is used inside the `unsafe` block:
+    ///
+    /// ```no_run
+    /// use std::ffi::{CString};
+    ///
+    /// let ptr = CString::new("Hello").unwrap().as_ptr();
+    /// unsafe {
+    ///     // `ptr` is dangling
+    ///     *ptr;
+    /// }
+    /// ```
+    ///
+    /// This happens because the pointer returned by `as_ptr` does not carry any
+    /// lifetime information and the string is deallocated immediately after
+    /// the `CString::new("Hello").unwrap().as_ptr()` expression is evaluated.
+    /// To fix the problem, bind the string to a local variable:
+    ///
+    /// ```no_run
+    /// use std::ffi::{CString};
+    ///
+    /// let hello = CString::new("Hello").unwrap();
+    /// let ptr = hello.as_ptr();
+    /// unsafe {
+    ///     // `ptr` is valid because `hello` is in scope
+    ///     *ptr;
+    /// }
+    /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn as_ptr(&self) -> *const c_char {
         self.inner.as_ptr()