Auto merge of #1217 - Susurrus:rfc_2235, r=gnzlbg

RFC 2235 - Implement PartialEq,Eq,Hash,Debug for all types

First pass at implementing [RFC2235](https://github.com/rust-lang/rfcs/blob/master/text/2235-libc-struct-traits.md). I just started with `PartialEq`/`Eq` and tested locally on my x64 Linux system. Definitely going to run into other types for other platforms that need this treatment, but thought I'd start small.

Open question is whether this should also rely on the `align` feature, which should improve which types can be auto-derived versus manually implemented (as it removed a lot of odd-sized padding arrays). My first pass here doesn't do that, but I might test it out to see if it does simplify quite a few structs. I think it might also be nice to have as it makes it easier for contributors to add new structs.

Part of rust-lang/rust#57715

Author: bors

.gitignore

@@ -1,3 +1,4 @@
 target
 Cargo.lock
 *~
+style

Cargo.lock

@@ -27,6 +27,7 @@ default = ["use_std"]
 use_std = []
 align = []
 rustc-dep-of-std = ['align', 'rustc-std-workspace-core']
+extra_traits = ["align"]
 
 [workspace]
 members = ["libc-test"]

Cargo.toml

@@ -44,6 +44,16 @@ activate the *align* feature. This requires Rust 1.25 or newer:
 libc = { version = "0.2", features = ["align"] }
 ```
 
+All structs implemented by the libc crate have the `Copy` and `Clone` traits
+implemented for them. The additional traits of `Debug, `Eq`, `Hash`, and
+`PartialEq` can be enabled with the *extra_traits* feature (requires Rust 1.25
+or newer):
+
+```toml
+[dependencies]
+libc = { version = "0.2", features = ["extra_traits"] }
+```
+
 ## What is libc?
 
 The primary purpose of this crate is to provide all of the definitions necessary

README.md

@@ -96,4 +96,8 @@ fi
 if [ "$(rustc --version | sed -E 's/^rustc 1\.([0-9]*)\..*/\1/')" -ge 25 ]; then
   cargo test $opt --features align --manifest-path libc-test/Cargo.toml --target "${TARGET}"
 fi
+# Test the `extra_traits` feature if this is building on Rust >= 1.25
+if [ "$(rustc --version | sed -E 's/^rustc 1\.([0-9]*)\..*/\1/')" -ge 25 ]; then
+  cargo test $opt --features extra_traits --manifest-path libc-test/Cargo.toml --target "${TARGET}"
+fi
 exec cargo test $opt --manifest-path libc-test/Cargo.toml --target "${TARGET}"

ci/run.sh

@@ -15,6 +15,7 @@ ctest = "0.2.8"
 default = [ "use_std" ]
 use_std = [ "libc/use_std" ]
 align = [ "libc/align" ]
+extra_traits = [ "libc/extra_traits" ]
 
 [[test]]
 name = "main"