From da3f3a3ab13fb335b525d74a38e6a8634a117fe5 Mon Sep 17 00:00:00 2001
From: Adrian Taylor <ade@hohum.me.uk>
Date: Sun, 3 Oct 2021 09:35:10 -0700
Subject: Avoid case of a self-referential type alias.

This previously produced a type alias which referred to itself,
which was clearly wrong and resulted in downstream code recursing
infinitely.

The problem case (per bug #2102) is:

  template <typename> class B{};
  template <typename c> class C {
  public:
    using U = B<c>;
  };
  class A : C<A> {
    U u;
  };

As far as I can tell, we parse clang's definition of B<A>; that leads
us to parse A; to find it has a field U which turns out to be of type
B<A>. And so we hit the line in item.rs which says:
  debug!("Avoiding recursion parsing type: {:?}", ty);
and bail out, returning the original item ID: hence, a self-
referential typedef is created.

The 'fix' in this PR creates an opaque type in this case instead,
to avoid later infinite loops. It would be preferable to avoid this
situation in the first place, but presumably that would require
us to split the parsing phase into two:
1) types
2) fields within those types.

Fixes #2102.
---
 src/ir/ty.rs                                       | 11 ++++-
 .../tests/constified-enum-module-overflow.rs       | 54 ++++++++++++++++++++++
 tests/headers/constified-enum-module-overflow.hpp  |  8 ++++
 3 files changed, 72 insertions(+), 1 deletion(-)
 create mode 100644 tests/expectations/tests/constified-enum-module-overflow.rs
 create mode 100644 tests/headers/constified-enum-module-overflow.hpp

diff --git a/src/ir/ty.rs b/src/ir/ty.rs
index 9cfbd7a9..d573408c 100644
--- a/src/ir/ty.rs
+++ b/src/ir/ty.rs
@@ -1082,7 +1082,16 @@ impl Type {
                     let inner = cursor.typedef_type().expect("Not valid Type?");
                     let inner =
                         Item::from_ty_or_ref(inner, location, None, ctx);
-                    TypeKind::Alias(inner)
+                    if inner == potential_id {
+                        warn!(
+                            "Generating oqaque type instead of self-referential \
+                            typedef");
+                        // This can happen if we bail out of recursive situations
+                        // within the clang parsing.
+                        TypeKind::Opaque
+                    } else {
+                        TypeKind::Alias(inner)
+                    }
                 }
                 CXType_Enum => {
                     let enum_ = Enum::from_ty(ty, ctx).expect("Not an enum?");
diff --git a/tests/expectations/tests/constified-enum-module-overflow.rs b/tests/expectations/tests/constified-enum-module-overflow.rs
new file mode 100644
index 00000000..4a799ef8
--- /dev/null
+++ b/tests/expectations/tests/constified-enum-module-overflow.rs
@@ -0,0 +1,54 @@
+#![allow(
+    dead_code,
+    non_snake_case,
+    non_camel_case_types,
+    non_upper_case_globals
+)]
+
+#[repr(C)]
+#[derive(Debug, Default, Copy, Clone)]
+pub struct B {
+    pub _address: u8,
+}
+#[repr(C)]
+#[derive(Debug, Default, Copy, Clone)]
+pub struct C {
+    pub _address: u8,
+}
+pub type C_U = B;
+#[repr(C)]
+#[derive(Debug, Default, Copy, Clone)]
+pub struct A {
+    pub u: u8,
+}
+#[test]
+fn bindgen_test_layout_A() {
+    assert_eq!(
+        ::std::mem::size_of::<A>(),
+        1usize,
+        concat!("Size of: ", stringify!(A))
+    );
+    assert_eq!(
+        ::std::mem::align_of::<A>(),
+        1usize,
+        concat!("Alignment of ", stringify!(A))
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<A>())).u as *const _ as usize },
+        0usize,
+        concat!("Offset of field: ", stringify!(A), "::", stringify!(u))
+    );
+}
+#[test]
+fn __bindgen_test_layout_C_open0_A_close0_instantiation() {
+    assert_eq!(
+        ::std::mem::size_of::<C>(),
+        1usize,
+        concat!("Size of template specialization: ", stringify!(C))
+    );
+    assert_eq!(
+        ::std::mem::align_of::<C>(),
+        1usize,
+        concat!("Alignment of template specialization: ", stringify!(C))
+    );
+}
diff --git a/tests/headers/constified-enum-module-overflow.hpp b/tests/headers/constified-enum-module-overflow.hpp
new file mode 100644
index 00000000..d48f2be1
--- /dev/null
+++ b/tests/headers/constified-enum-module-overflow.hpp
@@ -0,0 +1,8 @@
+template <typename> class B{};
+template <typename c> class C {
+public:
+  using U = B<c>;
+};
+class A : C<A> {
+  U u;
+};
-- 
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