Handle pointer constness at the right level.

src/codegen/mod.rs

@@ -3054,7 +3054,7 @@ impl TryToRustTy for Type {
             }
             TypeKind::Pointer(inner) |
             TypeKind::Reference(inner) => {
-                let is_const = self.is_const() || ctx.resolve_type(inner).is_const();
+                let is_const = ctx.resolve_type(inner).is_const();
 
                 let inner = inner.into_resolver().through_type_refs().resolve(ctx);
                 let inner_ty = inner.expect_type();

src/ir/ty.rs

@@ -1195,22 +1195,7 @@ impl Type {
 
         let name = if name.is_empty() { None } else { Some(name) };
 
-        // Just using ty.is_const() is wrong here, because when we declare an
-        // argument like 'int* const arg0', arg0 is considered
-        // const but the pointer itself points to mutable data.
-        //
-        // Without canonicalizing the type to the pointer type, we'll get the
-        // following mapping:
-        //
-        // arg0: *const c_int
-        //
-        // So by canonicalizing the type first, we can check constness by
-        // calling is_const() on the pointer type.
-        let is_const = if let Some(pty) = ty.pointee_type() {
-            pty.is_const()
-        } else {
-            ty.is_const()
-        };
+        let is_const = ty.is_const();
 
         let ty = Type::new(name, layout, kind, is_const);
         // TODO: maybe declaration.canonical()?

tests/expectations/tests/const-const-mut-ptr.rs

@@ -0,0 +1,32 @@
+/* automatically generated by rust-bindgen */
+
+#![allow(dead_code, non_snake_case, non_camel_case_types, non_upper_case_globals)]
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct foo {
+    pub bar: *const *const *mut *const ::std::os::raw::c_int,
+}
+#[test]
+fn bindgen_test_layout_foo() {
+    assert_eq!(
+        ::std::mem::size_of::<foo>(),
+        8usize,
+        concat!("Size of: ", stringify!(foo))
+    );
+    assert_eq!(
+        ::std::mem::align_of::<foo>(),
+        8usize,
+        concat!("Alignment of ", stringify!(foo))
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<foo>())).bar as *const _ as usize },
+        0usize,
+        concat!("Offset of field: ", stringify!(foo), "::", stringify!(bar))
+    );
+}
+impl Default for foo {
+    fn default() -> Self {
+        unsafe { ::std::mem::zeroed() }
+    }
+}

tests/headers/const-const-mut-ptr.h

@@ -0,0 +1,3 @@
+struct foo {
+  const int** const* const* bar;
+};