add test for insufficiently aligned vtable

Author: RalfJung

src/test/ui/consts/const-eval/ub-wide-ptr.rs

@@ -104,6 +104,8 @@ const TRAIT_OBJ_SHORT_VTABLE_2: &dyn Trait = unsafe { mem::transmute((&92u8, &3u
 // bad trait object
 const TRAIT_OBJ_INT_VTABLE: &dyn Trait = unsafe { mem::transmute((&92u8, 4usize)) };
 //~^ ERROR it is undefined behavior to use this value
+const TRAIT_OBJ_UNALIGNED_VTABLE: &dyn Trait = unsafe { mem::transmute((&92u8, &[0u8; 128])) };
+//~^ ERROR it is undefined behavior to use this value
 
 // bad data *inside* the trait object
 const TRAIT_OBJ_CONTENT_INVALID: &dyn Trait = unsafe { mem::transmute::<_, &bool>(&3u8) };

src/test/ui/consts/const-eval/ub-wide-ptr.stderr

@@ -159,41 +159,49 @@ LL | const TRAIT_OBJ_INT_VTABLE: &dyn Trait = unsafe { mem::transmute((&92u8, 4u
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:109:1
+  --> $DIR/ub-wide-ptr.rs:107:1
+   |
+LL | const TRAIT_OBJ_UNALIGNED_VTABLE: &dyn Trait = unsafe { mem::transmute((&92u8, &[0u8; 128])) };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered dangling or unaligned vtable pointer in wide pointer or too small vtable
+   |
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/ub-wide-ptr.rs:111:1
    |
 LL | const TRAIT_OBJ_CONTENT_INVALID: &dyn Trait = unsafe { mem::transmute::<_, &bool>(&3u8) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0x03 at .<deref>.<dyn-downcast>, but expected a boolean
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:113:1
+  --> $DIR/ub-wide-ptr.rs:115:1
    |
 LL | const RAW_TRAIT_OBJ_VTABLE_NULL: *const dyn Trait = unsafe { mem::transmute((&92u8, 0usize)) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered dangling or unaligned vtable pointer in wide pointer or too small vtable
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/ub-wide-ptr.rs:115:1
+  --> $DIR/ub-wide-ptr.rs:117:1
    |
 LL | const RAW_TRAIT_OBJ_VTABLE_INVALID: *const dyn Trait = unsafe { mem::transmute((&92u8, &3u64)) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered dangling or unaligned vtable pointer in wide pointer or too small vtable
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 error[E0080]: could not evaluate static initializer
-  --> $DIR/ub-wide-ptr.rs:121:5
+  --> $DIR/ub-wide-ptr.rs:123:5
    |
 LL |     mem::transmute::<_, &dyn Trait>((&92u8, 0usize))
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ inbounds test failed: 0x0 is not a valid pointer
 
 error[E0080]: could not evaluate static initializer
-  --> $DIR/ub-wide-ptr.rs:125:5
+  --> $DIR/ub-wide-ptr.rs:127:5
    |
 LL |     mem::transmute::<_, &dyn Trait>((&92u8, &3u64))
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: pointer must be in-bounds at offset N, but is outside bounds of allocN which has size N
 
-error: aborting due to 24 previous errors
+error: aborting due to 25 previous errors
 
 For more information about this error, try `rustc --explain E0080`.