Remove ZStr and ZString. (#337)

* Remove `ZStr` and `ZString`.

Use `CStr` and `CString` instead, now that nightly has then in core and
alloc, respectively.

Fixes #336.

* Enable "core_c_str" on nightly to use core::ffi::CStr.

* Don't test --no-default-features on stable.

--no-default-features disables "std", and building without "std" will
require nightly now.

* `CString` and `NulError` are in alloc.

* Add comments to the relevant Cargo.toml features.

* rustfmt

.github/workflows/main.yml

@@ -107,11 +107,8 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        build: [stable, nightly]
+        build: [nightly]
         include:
-          - build: stable
-            os: ubuntu-latest
-            rust: stable
           - build: nightly
             os: ubuntu-latest
             rust: nightly

Cargo.toml

@@ -91,7 +91,12 @@ targets = [
 
 [features]
 default = ["std"]
+
+# This enables use of std. Disabling this enables no_std, and
+# requires nightly Rust.
 std = ["io-lifetimes"]
+
+# This is used in the port of std to rustix.
 rustc-dep-of-std = [
     "core",
     "alloc",

benches/mod.rs

@@ -62,7 +62,7 @@ mod suite {
                     assert_eq!(
                         libc::fstatat(
                             libc::AT_FDCWD,
-                            rustix::zstr!("/").as_ptr() as _,
+                            rustix::cstr!("/").as_ptr() as _,
                             s.as_mut_ptr(),
                             0
                         ),
@@ -78,7 +78,7 @@ mod suite {
 
         c.bench_function("simple statat cstr", |b| {
             b.iter(|| {
-                statat(cwd(), rustix::zstr!("/"), AtFlags::empty()).unwrap();
+                statat(cwd(), rustix::cstr!("/"), AtFlags::empty()).unwrap();
             })
         });
     }

build.rs

@@ -16,11 +16,9 @@ fn main() {
     // Features only used in no-std configurations.
     #[cfg(not(feature = "std"))]
     {
-        use_feature_or_nothing("vec_into_raw_parts");
-        use_feature_or_nothing("toowned_clone_into");
-        use_feature_or_nothing("specialization");
-        use_feature_or_nothing("slice_internals");
         use_feature_or_nothing("const_raw_ptr_deref");
+        use_feature_or_nothing("core_c_str");
+        use_feature_or_nothing("alloc_c_string");
     }
 
     // Gather target information.

src/zstr.rs → src/cstr.rs

@@ -1,29 +1,29 @@
-/// A macro for [`ZStr`] literals.
+/// A macro for [`CStr`] literals.
 ///
 /// This can make passing string literals to rustix APIs more efficient, since
 /// most underlying system calls with string arguments expect NUL-terminated
-/// strings, and passing strings to rustix as `ZStr`s means that rustix doesn't
+/// strings, and passing strings to rustix as `CStr`s means that rustix doesn't
 /// need to copy them into a separate buffer to NUL-terminate them.
 ///
-/// [`ZStr`]: crate::ffi::ZStr
+/// [`CStr`]: crate::ffi::CStr
 ///
 /// # Examples
 ///
 /// ```rust,no_run
 /// # #[cfg(feature = "fs")]
 /// # fn main() -> rustix::io::Result<()> {
+/// use rustix::cstr;
 /// use rustix::fs::{cwd, statat, AtFlags};
-/// use rustix::zstr;
 ///
-/// let metadata = statat(cwd(), zstr!("test.txt"), AtFlags::empty())?;
+/// let metadata = statat(cwd(), cstr!("test.txt"), AtFlags::empty())?;
 /// # Ok(())
 /// # }
 /// # #[cfg(not(feature = "fs"))]
 /// # fn main() {}
 /// ```
 #[allow(unused_macros)]
 #[macro_export]
-macro_rules! zstr {
+macro_rules! cstr {
     ($str:literal) => {{
         // Check for NUL manually, to ensure safety.
         //
@@ -35,7 +35,7 @@ macro_rules! zstr {
         // constant-fold away.
         assert!(
             !$str.bytes().any(|b| b == b'\0'),
-            "zstr argument contains embedded NUL bytes",
+            "cstr argument contains embedded NUL bytes",
         );
 
         #[allow(unsafe_code, unused_unsafe)]
@@ -47,30 +47,30 @@ macro_rules! zstr {
             // Safety: We have manually checked that the string does not contain
             // embedded NULs above, and we append or own NUL terminator here.
             unsafe {
-                $crate::ffi::ZStr::from_bytes_with_nul_unchecked(concat!($str, "\0").as_bytes())
+                $crate::ffi::CStr::from_bytes_with_nul_unchecked(concat!($str, "\0").as_bytes())
             }
         }
     }};
 }
 
 #[test]
-fn test_zstr() {
-    use crate::ffi::ZString;
+fn test_cstr() {
+    use crate::ffi::CString;
     use alloc::borrow::ToOwned;
-    assert_eq!(zstr!(""), &*ZString::new("").unwrap());
-    assert_eq!(zstr!("").to_owned(), ZString::new("").unwrap());
-    assert_eq!(zstr!("hello"), &*ZString::new("hello").unwrap());
-    assert_eq!(zstr!("hello").to_owned(), ZString::new("hello").unwrap());
+    assert_eq!(cstr!(""), &*CString::new("").unwrap());
+    assert_eq!(cstr!("").to_owned(), CString::new("").unwrap());
+    assert_eq!(cstr!("hello"), &*CString::new("hello").unwrap());
+    assert_eq!(cstr!("hello").to_owned(), CString::new("hello").unwrap());
 }
 
 #[test]
 #[should_panic]
-fn test_invalid_zstr() {
-    let _ = zstr!("hello\0world");
+fn test_invalid_cstr() {
+    let _ = cstr!("hello\0world");
 }
 
 #[test]
 #[should_panic]
-fn test_invalid_empty_zstr() {
-    let _ = zstr!("\0");
+fn test_invalid_empty_cstr() {
+    let _ = cstr!("\0");
 }

src/ffi/mod.rs

@@ -1,24 +1,9 @@
 //! Utilities related to FFI bindings.
 
-/// Minimal and unoptimized `strlen` implementation.
-///
-/// TODO: Optimize this by reading a `usize` at a time.
 #[cfg(not(feature = "std"))]
-#[allow(unsafe_code)]
-unsafe fn strlen(mut s: *const u8) -> usize {
-    let mut len = 0;
-    while *s != b'\0' {
-        len += 1;
-        s = s.add(1);
-    }
-    len
-}
-
-#[cfg(not(feature = "std"))]
-mod z_str;
-
+pub use alloc::ffi::{CString, NulError};
 #[cfg(not(feature = "std"))]
-pub use z_str::{FromBytesWithNulError, FromVecWithNulError, NulError, ZStr, ZString};
+pub use core::ffi::{CStr, FromBytesWithNulError};
 
 #[cfg(feature = "std")]
-pub use std::ffi::{CStr as ZStr, CString as ZString, FromBytesWithNulError, NulError};
+pub use std::ffi::{CStr, CString, FromBytesWithNulError, NulError};