ty: Use canonical type to access pointee.

Using the canonical type fixes this but changes the output of some tests
(in particular, pointer to typedefs now point to the underlying type).
So do this only in known-bad cases.

Fixes #2244

3 files changed, 21 insertions, 1 deletions

diff --git a/src/ir/ty.rs b/src/ir/ty.rs
index d573408c..38ab4564 100644
--- a/src/ir/ty.rs
+++ b/src/ir/ty.rs
@@ -1031,7 +1031,16 @@ impl Type {
                 CXType_ObjCObjectPointer |
                 CXType_MemberPointer |
                 CXType_Pointer => {
-                    let pointee = ty.pointee_type().unwrap();
+                    let mut pointee = ty.pointee_type().unwrap();
+                    if *ty != canonical_ty {
+                        let canonical_pointee =
+                            canonical_ty.pointee_type().unwrap();
+                        // clang sometimes loses pointee constness here, see
+                        // #2244.
+                        if canonical_pointee.is_const() != pointee.is_const() {
+                            pointee = canonical_pointee;
+                        }
+                    }
                     let inner =
                         Item::from_ty_or_ref(pointee, location, None, ctx);
                     TypeKind::Pointer(inner)
diff --git a/tests/expectations/tests/pointer-attr.rs b/tests/expectations/tests/pointer-attr.rs
new file mode 100644
index 00000000..95fe9c5f
--- /dev/null
+++ b/tests/expectations/tests/pointer-attr.rs
@@ -0,0 +1,10 @@
+#![allow(
+    dead_code,
+    non_snake_case,
+    non_camel_case_types,
+    non_upper_case_globals
+)]
+
+extern "C" {
+    pub fn a(arg1: *const ::std::os::raw::c_char);
+}
diff --git a/tests/headers/pointer-attr.h b/tests/headers/pointer-attr.h
new file mode 100644
index 00000000..fe0004b8
--- /dev/null
+++ b/tests/headers/pointer-attr.h
@@ -0,0 +1 @@
+void a(const char __attribute__((btf_type_tag("a"))) *);