Add rust language editions support

Introduce a new `--rust-edition` parameter with allowed values 2015, 2018, 2021, and 2024.

This allows different code generation depending on the language target.  In this PR, the C-string literals are now generated differently depending on the language edition (literals like `c"example"` are not available before 2021)

Author: nyurik

bindgen-tests/tests/expectations/tests/strings_cstr2.rs

@@ -0,0 +1,5 @@
+// bindgen-flags: --rust-target=1.77 --rust-edition=2021 --generate-cstr
+
+const char* MY_STRING_UTF8 = "Hello, world!";
+const char* MY_STRING_INTERIOR_NULL = "Hello,\0World!";
+const char* MY_STRING_NON_UTF8 = "ABCDE\xFF";

bindgen-tests/tests/expectations/tests/strings_cstr2_2021.rs

@@ -60,6 +60,7 @@ use quote::{ToTokens, TokenStreamExt};
 use crate::{Entry, HashMap, HashSet};
 use std::borrow::Cow;
 use std::cell::Cell;
+use std::cmp::{Ordering, PartialOrd};
 use std::collections::VecDeque;
 use std::ffi::CStr;
 use std::fmt::{self, Write};
@@ -726,7 +727,9 @@ impl CodeGenerator for Var {
 
                     if let Some(cstr) = cstr {
                         let cstr_ty = quote! { ::#prefix::ffi::CStr };
-                        if rust_features.literal_cstr {
+                        if rust_features.literal_cstr &&
+                            options.rust_edition >= RustEdition::Rust2021
+                        {
                             let cstr = proc_macro2::Literal::c_string(&cstr);
                             result.push(quote! {
                                 #(#attrs)*
@@ -3913,6 +3916,67 @@ impl std::str::FromStr for MacroTypeVariation {
     }
 }
 
+/// Enum for the edition of Rust language to use.
+#[derive(Copy, Clone, PartialEq, Eq, Debug, Default)]
+pub enum RustEdition {
+    /// Rust 2015 language edition
+    Rust2015,
+    /// Rust 2018 language edition
+    #[default]
+    Rust2018,
+    /// Rust 2021 language edition
+    Rust2021,
+    /// Rust 2024 language edition
+    Rust2024,
+}
+
+impl From<RustEdition> for usize {
+    fn from(edition: RustEdition) -> usize {
+        match edition {
+            RustEdition::Rust2015 => 2015,
+            RustEdition::Rust2018 => 2018,
+            RustEdition::Rust2021 => 2021,
+            RustEdition::Rust2024 => 2024,
+        }
+    }
+}
+
+impl fmt::Display for RustEdition {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let value: usize = (*self).into();
+        value.fmt(f)
+    }
+}
+
+impl FromStr for RustEdition {
+    type Err = std::io::Error;
+
+    /// Create a `RustEdition` from a string.
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "2015" => Ok(RustEdition::Rust2015),
+            "2018" => Ok(RustEdition::Rust2018),
+            "2021" => Ok(RustEdition::Rust2021),
+            "2024" => Ok(RustEdition::Rust2024),
+            _ => Err(std::io::Error::new(
+                std::io::ErrorKind::InvalidInput,
+                concat!(
+                    "Got an invalid language edition. Accepted values ",
+                    "are '2015', '2018', '2021', and '2024'"
+                ),
+            )),
+        }
+    }
+}
+
+impl PartialOrd for RustEdition {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        let a: usize = (*self).into();
+        let b: usize = (*other).into();
+        a.partial_cmp(&b)
+    }
+}
+
 /// Enum for how aliases should be translated.
 #[derive(Copy, Clone, PartialEq, Eq, Debug, Default)]
 pub enum AliasVariation {

bindgen-tests/tests/headers/strings_cstr2_2021.h

@@ -161,7 +161,7 @@ define_rust_targets! {
     },
     Stable_1_77(77) => {
         offset_of: #106655,
-        literal_cstr: #117472,
+        literal_cstr: #117472,  // Edition 2021+ only
     },
     Stable_1_73(73) => { thiscall_abi: #42202 },
     Stable_1_71(71) => { c_unwind_abi: #106075 },

bindgen/codegen/mod.rs

@@ -64,6 +64,7 @@ use ir::item::Item;
 use options::BindgenOptions;
 use parse::ParseError;
 
+use crate::codegen::RustEdition;
 use std::borrow::Cow;
 use std::collections::hash_map::Entry;
 use std::env;
@@ -528,6 +529,11 @@ impl BindgenOptions {
         }
     }
 
+    /// Update rust edition version
+    pub fn set_rust_edition(&mut self, rust_edition: RustEdition) {
+        self.rust_edition = rust_edition;
+    }
+
     /// Update rust target version
     pub fn set_rust_target(&mut self, rust_target: RustTarget) {
         self.rust_target = rust_target;

bindgen/features.rs

@@ -7,7 +7,7 @@ use crate::{
     regex_set::RegexSet,
     Abi, AliasVariation, Builder, CodegenConfig, EnumVariation,
     FieldVisibilityKind, Formatter, MacroTypeVariation, NonCopyUnionStyle,
-    RustTarget,
+    RustEdition, RustTarget,
 };
 use clap::{
     error::{Error, ErrorKind},
@@ -19,6 +19,13 @@ use std::path::{Path, PathBuf};
 use std::str::FromStr;
 use std::{fs::File, process::exit};
 
+fn rust_edition_help() -> String {
+    format!(
+        "Version of the Rust language edition. Defaults to {}.",
+        RustEdition::default()
+    )
+}
+
 fn rust_target_help() -> String {
     format!(
         "Version of the Rust compiler to target. Any Rust version after {EARLIEST_STABLE_RUST} is supported. Defaults to {}.",
@@ -332,6 +339,8 @@ struct BindgenCommand {
     /// Add a RAW_LINE of Rust code to a given module with name MODULE_NAME.
     #[arg(long, number_of_values = 2, value_names = ["MODULE_NAME", "RAW_LINE"])]
     module_raw_line: Vec<String>,
+    #[arg(long, help = rust_edition_help())]
+    rust_edition: Option<RustEdition>,
     #[arg(long, help = rust_target_help())]
     rust_target: Option<RustTarget>,
     /// Use types from Rust core instead of std.
@@ -587,6 +596,7 @@ where
         output,
         raw_line,
         module_raw_line,
+        rust_edition,
         rust_target,
         use_core,
         conservative_inline_namespaces,
@@ -820,6 +830,7 @@ where
                 exit(0)
             },
             header,
+            rust_edition,
             rust_target,
             default_enum_style,
             bitfield_enum,

bindgen/lib.rs

@@ -10,6 +10,7 @@ pub(crate) mod cli;
 use crate::callbacks::ParseCallbacks;
 use crate::codegen::{
     AliasVariation, EnumVariation, MacroTypeVariation, NonCopyUnionStyle,
+    RustEdition,
 };
 use crate::deps::DepfileSpec;
 use crate::features::{RustFeatures, RustTarget};
@@ -1594,6 +1595,23 @@ options! {
         as_args: |value, args| (!value).as_args(args, "--no-prepend-enum-name"),
     },
     /// Version of the Rust compiler to target.
+    rust_edition: RustEdition {
+        default: RustEdition::default(),
+        methods: {
+            /// Specify the Rust edition version.
+            ///
+            /// The default edition is 2018.
+            pub fn rust_edition(mut self, rust_edition: RustEdition) -> Self {
+                self.options.set_rust_edition(rust_edition);
+                self
+            }
+        },
+        as_args: |rust_edition, args| {
+            args.push("--rust-edition".to_owned());
+            args.push(rust_edition.to_string());
+        },
+    },
+    /// Version of the Rust compiler to target.
     rust_target: RustTarget {
         methods: {
             /// Specify the Rust target version.