Added support for #[repr(transparent)]

src/bindgen/ir/enumeration.rs

@@ -87,6 +87,7 @@ impl EnumVariant {
                 generic_params: GenericParams::default(),
                 fields: parse_fields(is_tagged, &fields.named)?,
                 is_tagged,
+                is_transparent: false,
                 tuple_struct: false,
                 cfg: Cfg::append(mod_cfg, Cfg::load(&variant.attrs)),
                 annotations: AnnotationSet::load(&variant.attrs)?,
@@ -97,6 +98,7 @@ impl EnumVariant {
                 generic_params: GenericParams::default(),
                 fields: parse_fields(is_tagged, &fields.unnamed)?,
                 is_tagged,
+                is_transparent: false,
                 tuple_struct: true,
                 cfg: Cfg::append(mod_cfg, Cfg::load(&variant.attrs)),
                 annotations: AnnotationSet::load(&variant.attrs)?,

src/bindgen/ir/repr.rs

@@ -4,10 +4,11 @@
 
 use syn;
 
-#[derive(Debug, Copy, Clone, PartialEq)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
 pub enum ReprStyle {
     Rust,
     C,
+    Transparent,
 }
 
 impl Default for ReprStyle {
@@ -16,7 +17,7 @@ impl Default for ReprStyle {
     }
 }
 
-#[derive(Debug, Copy, Clone, PartialEq)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
 pub enum ReprType {
     U8,
     U16,
@@ -28,7 +29,7 @@ pub enum ReprType {
     ISize,
 }
 
-#[derive(Debug, Copy, Clone, PartialEq, Default)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Default)]
 pub struct Repr {
     pub style: ReprStyle,
     pub ty: Option<ReprType>,
@@ -40,6 +41,11 @@ impl Repr {
         ty: None,
     };
 
+    pub const TRANSPARENT: Self = Repr {
+        style: ReprStyle::Transparent,
+        ty: None,
+    };
+
     pub const RUST: Self = Repr {
         style: ReprStyle::Rust,
         ty: None,
@@ -82,6 +88,10 @@ impl Repr {
                     repr.style = ReprStyle::C;
                     continue;
                 }
+                "transparent" => {
+                    repr.style = ReprStyle::Transparent;
+                    continue;
+                }
                 _ => {
                     return Err(format!("Unsupported #[repr({})].", id));
                 }

src/bindgen/ir/structure.rs

@@ -11,7 +11,7 @@ use bindgen::declarationtyperesolver::DeclarationTypeResolver;
 use bindgen::dependencies::Dependencies;
 use bindgen::ir::{
     AnnotationSet, Cfg, ConditionWrite, Documentation, GenericParams, Item, ItemContainer, Repr,
-    ToCondition, Type,
+    ToCondition, Type, Typedef,
 };
 use bindgen::library::Library;
 use bindgen::mangle;
@@ -26,6 +26,7 @@ pub struct Struct {
     pub generic_params: GenericParams,
     pub fields: Vec<(String, Type, Documentation)>,
     pub is_tagged: bool,
+    pub is_transparent: bool,
     pub tuple_struct: bool,
     pub cfg: Option<Cfg>,
     pub annotations: AnnotationSet,
@@ -39,9 +40,13 @@ impl Struct {
     }
 
     pub fn load(item: &syn::ItemStruct, mod_cfg: &Option<Cfg>) -> Result<Struct, String> {
-        if Repr::load(&item.attrs)? != Repr::C {
-            return Err("Struct is not marked #[repr(C)].".to_owned());
-        }
+        let is_transparent = match Repr::load(&item.attrs)? {
+            Repr::C => false,
+            Repr::TRANSPARENT => true,
+            _ => {
+                return Err("Struct is not marked #[repr(C)] or #[repr(transparent)].".to_owned());
+            }
+        };
 
         let (fields, tuple_struct) = match &item.fields {
             &syn::Fields::Unit => (Vec::new(), false),
@@ -70,6 +75,7 @@ impl Struct {
             generic_params: GenericParams::new(&item.generics),
             fields: fields,
             is_tagged: false,
+            is_transparent: is_transparent,
             tuple_struct: tuple_struct,
             cfg: Cfg::append(mod_cfg, Cfg::load(&item.attrs)),
             annotations: AnnotationSet::load(&item.attrs)?,
@@ -128,7 +134,9 @@ impl Item for Struct {
     }
 
     fn collect_declaration_types(&self, resolver: &mut DeclarationTypeResolver) {
-        resolver.add_struct(&self.name);
+        if !self.is_transparent {
+            resolver.add_struct(&self.name);
+        }
     }
 
     fn resolve_declaration_types(&mut self, resolver: &DeclarationTypeResolver) {
@@ -225,6 +233,7 @@ impl Item for Struct {
                 .map(|x| (x.0.clone(), x.1.specialize(&mappings), x.2.clone()))
                 .collect(),
             is_tagged: self.is_tagged,
+            is_transparent: self.is_transparent,
             tuple_struct: self.tuple_struct,
             cfg: self.cfg.clone(),
             annotations: self.annotations.clone(),
@@ -240,6 +249,18 @@ impl Item for Struct {
 
 impl Source for Struct {
     fn write<F: Write>(&self, config: &Config, out: &mut SourceWriter<F>) {
+        if self.is_transparent {
+            let typedef = Typedef {
+                name: self.name.clone(),
+                generic_params: self.generic_params.clone(),
+                aliased: self.fields[0].1.clone(),
+                cfg: self.cfg.clone(),
+                annotations: self.annotations.clone(),
+                documentation: self.documentation.clone(),
+            };
+            return typedef.write(config, out);
+        }
+
         let condition = (&self.cfg).to_condition(config);
         condition.write_before(config, out);
 

tests/expectations/both/transparent.c

@@ -0,0 +1,24 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+typedef struct DummyStruct DummyStruct;
+
+typedef DummyStruct TransparentComplexWrappingStructTuple;
+
+typedef uint32_t TransparentPrimitiveWrappingStructTuple;
+
+typedef DummyStruct TransparentComplexWrappingStructure;
+
+typedef uint32_t TransparentPrimitiveWrappingStructure;
+
+typedef DummyStruct TransparentComplexWrapper_i32;
+
+typedef uint32_t TransparentPrimitiveWrapper_i32;
+
+void root(TransparentComplexWrappingStructTuple a,
+          TransparentPrimitiveWrappingStructTuple b,
+          TransparentComplexWrappingStructure c,
+          TransparentPrimitiveWrappingStructure d,
+          TransparentComplexWrapper_i32 e,
+          TransparentPrimitiveWrapper_i32 f);

tests/expectations/tag/transparent.c

@@ -0,0 +1,24 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+struct DummyStruct;
+
+typedef struct DummyStruct TransparentComplexWrappingStructTuple;
+
+typedef uint32_t TransparentPrimitiveWrappingStructTuple;
+
+typedef struct DummyStruct TransparentComplexWrappingStructure;
+
+typedef uint32_t TransparentPrimitiveWrappingStructure;
+
+typedef struct DummyStruct TransparentComplexWrapper_i32;
+
+typedef uint32_t TransparentPrimitiveWrapper_i32;
+
+void root(TransparentComplexWrappingStructTuple a,
+          TransparentPrimitiveWrappingStructTuple b,
+          TransparentComplexWrappingStructure c,
+          TransparentPrimitiveWrappingStructure d,
+          TransparentComplexWrapper_i32 e,
+          TransparentPrimitiveWrapper_i32 f);

tests/expectations/transparent.c

@@ -0,0 +1,24 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+typedef struct DummyStruct DummyStruct;
+
+typedef DummyStruct TransparentComplexWrappingStructTuple;
+
+typedef uint32_t TransparentPrimitiveWrappingStructTuple;
+
+typedef DummyStruct TransparentComplexWrappingStructure;
+
+typedef uint32_t TransparentPrimitiveWrappingStructure;
+
+typedef DummyStruct TransparentComplexWrapper_i32;
+
+typedef uint32_t TransparentPrimitiveWrapper_i32;
+
+void root(TransparentComplexWrappingStructTuple a,
+          TransparentPrimitiveWrappingStructTuple b,
+          TransparentComplexWrappingStructure c,
+          TransparentPrimitiveWrappingStructure d,
+          TransparentComplexWrapper_i32 e,
+          TransparentPrimitiveWrapper_i32 f);

tests/expectations/transparent.cpp

@@ -0,0 +1,29 @@
+#include <cstdint>
+#include <cstdlib>
+
+struct DummyStruct;
+
+using TransparentComplexWrappingStructTuple = DummyStruct;
+
+using TransparentPrimitiveWrappingStructTuple = uint32_t;
+
+using TransparentComplexWrappingStructure = DummyStruct;
+
+using TransparentPrimitiveWrappingStructure = uint32_t;
+
+template<typename T>
+using TransparentComplexWrapper = DummyStruct;
+
+template<typename T>
+using TransparentPrimitiveWrapper = uint32_t;
+
+extern "C" {
+
+void root(TransparentComplexWrappingStructTuple a,
+          TransparentPrimitiveWrappingStructTuple b,
+          TransparentComplexWrappingStructure c,
+          TransparentPrimitiveWrappingStructure d,
+          TransparentComplexWrapper<int32_t> e,
+          TransparentPrimitiveWrapper<int32_t> f);
+
+} // extern "C"

tests/rust/transparent.rs

@@ -0,0 +1,41 @@
+struct DummyStruct;
+
+// Transparent struct tuple wrapping a struct.
+#[repr(transparent)]
+struct TransparentComplexWrappingStructTuple(DummyStruct);
+
+// Transparent struct tuple wrapping a primitive.
+#[repr(transparent)]
+struct TransparentPrimitiveWrappingStructTuple(u32);
+
+// Transparent structure wrapping a struct.
+#[repr(transparent)]
+struct TransparentComplexWrappingStructure { only_field: DummyStruct }
+
+// Transparent structure wrapping a primitive.
+#[repr(transparent)]
+struct TransparentPrimitiveWrappingStructure { only_field: u32 }
+
+// Transparent struct wrapper with a marker wrapping a struct.
+#[repr(transparent)]
+struct TransparentComplexWrapper<T> {
+    only_non_zero_sized_field: DummyStruct,
+    marker: PhantomData<T>,
+}
+
+// Transparent struct wrapper with a marker wrapping a primitive.
+#[repr(transparent)]
+struct TransparentPrimitiveWrapper<T> {
+    only_non_zero_sized_field: u32,
+    marker: PhantomData<T>,
+}
+
+#[no_mangle]
+pub extern "C" fn root(
+    a: TransparentComplexWrappingStructTuple,
+    b: TransparentPrimitiveWrappingStructTuple,
+    c: TransparentComplexWrappingStructure,
+    d: TransparentPrimitiveWrappingStructure,
+    e: TransparentComplexWrapper<i32>,
+    f: TransparentPrimitiveWrapper<i32>,
+) { }