From 069d8fdb71a9a46a76552e8eea7d427b4d6f08a1 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Sun, 5 Jun 2022 12:25:46 -0400
Subject: [PATCH] test for Stacked Borrows error during vtable validation

---
 tests/fail/stacked_borrows/vtable.rs     | 19 ++++++++++++++++++
 tests/fail/stacked_borrows/vtable.stderr | 25 ++++++++++++++++++++++++
 2 files changed, 44 insertions(+)
 create mode 100644 tests/fail/stacked_borrows/vtable.rs
 create mode 100644 tests/fail/stacked_borrows/vtable.stderr

diff --git a/tests/fail/stacked_borrows/vtable.rs b/tests/fail/stacked_borrows/vtable.rs
new file mode 100644
index 00000000000..dd9ba1dfb2b
--- /dev/null
+++ b/tests/fail/stacked_borrows/vtable.rs
@@ -0,0 +1,19 @@
+// error-pattern: vtable pointer does not have permission
+#![feature(ptr_metadata)]
+
+trait Foo {}
+
+impl Foo for u32 {}
+
+fn uwu(thin: *const (), meta: &'static ()) -> *const dyn Foo {
+    core::ptr::from_raw_parts(thin, unsafe { core::mem::transmute(meta) })
+}
+
+fn main() {
+    unsafe {
+        let orig = 1_u32;
+        let x = &orig as &dyn Foo;
+        let (ptr, meta) = (x as *const dyn Foo).to_raw_parts();
+        let _ = uwu(ptr, core::mem::transmute(meta));
+    }
+}
diff --git a/tests/fail/stacked_borrows/vtable.stderr b/tests/fail/stacked_borrows/vtable.stderr
new file mode 100644
index 00000000000..ac3d71045f0
--- /dev/null
+++ b/tests/fail/stacked_borrows/vtable.stderr
@@ -0,0 +1,25 @@
+error: Undefined Behavior: type validation failed: encountered vtable pointer does not have permission to read drop function pointer
+  --> RUSTLIB/core/src/ptr/metadata.rs:LL:CC
+   |
+LL |     unsafe { PtrRepr { components: PtrComponents { data_address, metadata } }.const_ptr }
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered vtable pointer does not have permission to read drop function pointer
+   |
+   = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
+   = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+           
+   = note: inside `std::ptr::from_raw_parts::<dyn Foo>` at RUSTLIB/core/src/ptr/metadata.rs:LL:CC
+note: inside `uwu` at $DIR/vtable.rs:LL:CC
+  --> $DIR/vtable.rs:LL:CC
+   |
+LL |     core::ptr::from_raw_parts(thin, unsafe { core::mem::transmute(meta) })
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+note: inside `main` at $DIR/vtable.rs:LL:CC
+  --> $DIR/vtable.rs:LL:CC
+   |
+LL |         let _ = uwu(ptr, core::mem::transmute(meta));
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to previous error
+