Add option to translate enum integer types to native Rust integer types

Fixes rust-lang#430

Author: Jethro Beekman

src/codegen/mod.rs

@@ -2524,7 +2524,7 @@ impl<'a> EnumBuilder<'a> {
     /// the representation, and which variation it should be generated as.
     fn new(
         name: &'a str,
-        attrs: Vec<proc_macro2::TokenStream>,
+        mut attrs: Vec<proc_macro2::TokenStream>,
         repr: proc_macro2::TokenStream,
         enum_variation: EnumVariation,
         enum_codegen_depth: usize,
@@ -2543,6 +2543,8 @@ impl<'a> EnumBuilder<'a> {
             },
 
             EnumVariation::Rust { .. } => {
+                // `repr` is guaranteed to be Rustified in Enum::codegen
+                attrs.push(quote! { #[repr( #repr )] });
                 let tokens = quote!();
                 EnumBuilder::Rust {
                     codegen_depth: enum_codegen_depth + 1,
@@ -2820,51 +2822,73 @@ impl CodeGenerator for Enum {
         let ident = ctx.rust_ident(&name);
         let enum_ty = item.expect_type();
         let layout = enum_ty.layout(ctx);
+        let variation = self.computed_enum_variation(ctx, item);
 
-        let repr = self.repr().map(|repr| ctx.resolve_type(repr));
-        let repr = match repr {
-            Some(repr) => match *repr.canonical_type(ctx).kind() {
-                TypeKind::Int(int_kind) => int_kind,
-                _ => panic!("Unexpected type as enum repr"),
-            },
-            None => {
-                warn!(
-                    "Guessing type of enum! Forward declarations of enums \
-                     shouldn't be legal!"
-                );
-                IntKind::Int
+        let repr_translated;
+        let repr = match self.repr().map(|repr| ctx.resolve_type(repr)) {
+            Some(repr)
+                if !ctx.options().translate_enum_integer_types &&
+                    !variation.is_rust() =>
+            {
+                repr
             }
-        };
+            repr => {
+                // An enum's integer type is translated to a native Rust
+                // integer type in 3 cases:
+                // * the enum is Rustified and we need a translated type for
+                //   the repr attribute
+                // * the representation couldn't be determined from the C source
+                // * it was explicitly requested as a bindgen option
+
+                let kind = match repr {
+                    Some(repr) => match *repr.canonical_type(ctx).kind() {
+                        TypeKind::Int(int_kind) => int_kind,
+                        _ => panic!("Unexpected type as enum repr"),
+                    },
+                    None => {
+                        warn!(
+                            "Guessing type of enum! Forward declarations of enums \
+                             shouldn't be legal!"
+                        );
+                        IntKind::Int
+                    }
+                };
+
+                let signed = kind.is_signed();
+                let size = layout
+                    .map(|l| l.size)
+                    .or_else(|| kind.known_size())
+                    .unwrap_or(0);
+
+                let translated = match (signed, size) {
+                    (true, 1) => IntKind::I8,
+                    (false, 1) => IntKind::U8,
+                    (true, 2) => IntKind::I16,
+                    (false, 2) => IntKind::U16,
+                    (true, 4) => IntKind::I32,
+                    (false, 4) => IntKind::U32,
+                    (true, 8) => IntKind::I64,
+                    (false, 8) => IntKind::U64,
+                    _ => {
+                        warn!(
+                            "invalid enum decl: signed: {}, size: {}",
+                            signed, size
+                        );
+                        IntKind::I32
+                    }
+                };
 
-        let signed = repr.is_signed();
-        let size = layout
-            .map(|l| l.size)
-            .or_else(|| repr.known_size())
-            .unwrap_or(0);
-
-        let repr_name = match (signed, size) {
-            (true, 1) => "i8",
-            (false, 1) => "u8",
-            (true, 2) => "i16",
-            (false, 2) => "u16",
-            (true, 4) => "i32",
-            (false, 4) => "u32",
-            (true, 8) => "i64",
-            (false, 8) => "u64",
-            _ => {
-                warn!("invalid enum decl: signed: {}, size: {}", signed, size);
-                "i32"
+                repr_translated =
+                    Type::new(None, None, TypeKind::Int(translated), false);
+                &repr_translated
             }
         };
 
         let mut attrs = vec![];
 
-        let variation = self.computed_enum_variation(ctx, item);
-
         // TODO(emilio): Delegate this to the builders?
         match variation {
             EnumVariation::Rust { non_exhaustive } => {
-                attrs.push(attributes::repr(repr_name));
                 if non_exhaustive &&
                     ctx.options().rust_features().non_exhaustive
                 {
@@ -2934,13 +2958,7 @@ impl CodeGenerator for Enum {
             });
         }
 
-        let repr = match self.repr() {
-            Some(ty) => ty.to_rust_ty_or_opaque(ctx, &()),
-            None => {
-                let repr_name = ctx.rust_ident_raw(repr_name);
-                quote! { #repr_name }
-            }
-        };
+        let repr = repr.to_rust_ty_or_opaque(ctx, item);
 
         let mut builder = EnumBuilder::new(
             &name,

src/lib.rs

@@ -549,6 +549,10 @@ impl Builder {
             output_vector.push("--respect-cxx-access-specs".into());
         }
 
+        if self.options.translate_enum_integer_types {
+            output_vector.push("--translate-enum-integer-types".into());
+        }
+
         // Add clang arguments
 
         output_vector.push("--".into());
@@ -1568,6 +1572,16 @@ impl Builder {
         self.options.respect_cxx_access_specs = doit;
         self
     }
+
+    /// Always translate enum integer types to native Rust integer types.
+    ///
+    /// This will result in enums having types such as `u32` and `i16` instead
+    /// of `c_uint` and `c_short`. Types for Rustified enums are always
+    /// translated.
+    pub fn translate_enum_integer_types(mut self, doit: bool) -> Self {
+        self.options.translate_enum_integer_types = doit;
+        self
+    }
 }
 
 /// Configuration options for generated bindings.
@@ -1859,6 +1873,9 @@ struct BindgenOptions {
     /// Only make generated bindings `pub` if the items would be publically accessible
     /// by C++.
     respect_cxx_access_specs: bool,
+
+    /// Always translate enum integer types to native Rust integer types.
+    translate_enum_integer_types: bool,
 }
 
 /// TODO(emilio): This is sort of a lie (see the error message that results from
@@ -1996,6 +2013,7 @@ impl Default for BindgenOptions {
             wasm_import_module_name: None,
             dynamic_library_name: None,
             respect_cxx_access_specs: false,
+            translate_enum_integer_types: false,
         }
     }
 }

src/options.rs

@@ -503,6 +503,9 @@ where
             Arg::with_name("respect-cxx-access-specs")
                 .long("respect-cxx-access-specs")
                 .help("Makes generated bindings `pub` only for items if the items are publically accessible in C++."),
+            Arg::with_name("translate-enum-integer-types")
+                .long("translate-enum-integer-types")
+                .help("Always translate enum integer types to native Rust integer types."),
         ]) // .args()
         .get_matches_from(args);
 
@@ -929,6 +932,10 @@ where
         builder = builder.respect_cxx_access_specs(true);
     }
 
+    if matches.is_present("translate-enum-integer-types") {
+        builder = builder.translate_enum_integer_types(true);
+    }
+
     let verbose = matches.is_present("verbose");
 
     Ok((builder, output, verbose))

tests/expectations/tests/libclang-9/enum-translate-type.rs

@@ -0,0 +1,15 @@
+#![allow(
+    dead_code,
+    non_snake_case,
+    non_camel_case_types,
+    non_upper_case_globals
+)]
+
+pub const my_enum1_A: my_enum1 = 0;
+pub type my_enum1 = u32;
+pub const my_enum2_B: my_enum2 = -1;
+pub type my_enum2 = i32;
+pub const my_enum3_C: my_enum3 = 0;
+pub type my_enum3 = i16;
+pub const my_enum4_D: my_enum4 = 255;
+pub type my_enum4 = u8;

tests/headers/enum-translate-type.h

@@ -0,0 +1,14 @@
+// bindgen-flags: --translate-enum-integer-types
+
+enum my_enum1 {
+    A = 0,
+};
+enum my_enum2 {
+    B = -1,
+};
+enum my_enum3: short {
+    C = 0,
+};
+enum my_enum4: unsigned char {
+    D = -1,
+};