Rollup merge of #114335 - RalfJung:ptr_comparisons, r=oli-obk

fix and extend ptr_comparison test

r? ```@oli-obk```

2 files changed, 8 insertions, 68 deletions

diff --git a/tests/ui/consts/ptr_comparisons.rs b/tests/ui/consts/ptr_comparisons.rs
index f442e613839..a5b6cd9d2d4 100644
--- a/tests/ui/consts/ptr_comparisons.rs
+++ b/tests/ui/consts/ptr_comparisons.rs
@@ -1,8 +1,5 @@
 // compile-flags: --crate-type=lib
-// normalize-stderr-32bit: "8 bytes" -> "$$TWO_WORDS bytes"
-// normalize-stderr-64bit: "16 bytes" -> "$$TWO_WORDS bytes"
-// normalize-stderr-32bit: "size 4" -> "size $$WORD"
-// normalize-stderr-64bit: "size 8" -> "size $$WORD"
+// check-pass
 
 #![feature(
     core_intrinsics,
@@ -34,30 +31,13 @@ check!(ne, unsafe { (FOO as *const usize as *const u8).offset(3) }, 0);
 
 // We want pointers to be equal to themselves, but aren't checking this yet because
 // there are some open questions (e.g. whether function pointers to the same function
-// compare equal, they don't necessarily at runtime).
-// The case tested here should work eventually, but does not work yet.
+// compare equal: they don't necessarily do at runtime).
 check!(!, FOO as *const _, FOO as *const _);
 
+// aside from 0, these pointers might end up pretty much anywhere.
+check!(!, FOO as *const _, 1); // this one could be `ne` by taking into account alignment
+check!(!, FOO as *const _, 1024);
 
-///////////////////////////////////////////////////////////////////////////////
-// If any of the below start compiling, make sure to add a `check` test for it.
-// These invocations exist as canaries so we don't forget to check that the
-// behaviour of `guaranteed_eq` and `guaranteed_ne` is still correct.
-// All of these try to obtain an out of bounds pointer in some manner. If we
-// can create out of bounds pointers, we can offset a pointer far enough that
-// at runtime it would be zero and at compile-time it would not be zero.
-
-const _: *const usize = unsafe { (FOO as *const usize).offset(2) };
-
-const _: *const u8 =
-    unsafe { std::ptr::addr_of!((*(FOO as *const usize as *const [u8; 1000]))[999]) };
-//~^ ERROR evaluation of constant value failed
-//~| out-of-bounds
-
-const _: usize = unsafe { std::mem::transmute::<*const usize, usize>(FOO) + 4 };
-//~^ ERROR evaluation of constant value failed
-//~| unable to turn pointer into raw bytes
-
-const _: usize = unsafe { *std::mem::transmute::<&&usize, &usize>(&FOO) + 4 };
-//~^ ERROR evaluation of constant value failed
-//~| unable to turn pointer into raw bytes
+// When pointers go out-of-bounds, they *might* become null, so these comparions cannot work.
+check!(!, unsafe { (FOO as *const usize).wrapping_add(2) }, 0);
+check!(!, unsafe { (FOO as *const usize).wrapping_sub(1) }, 0);
diff --git a/tests/ui/consts/ptr_comparisons.stderr b/tests/ui/consts/ptr_comparisons.stderr
deleted file mode 100644
index fea924d12e5..00000000000
--- a/tests/ui/consts/ptr_comparisons.stderr
+++ /dev/null
@@ -1,40 +0,0 @@
-error[E0080]: evaluation of constant value failed
-  --> $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
-   |
-   = note: out-of-bounds pointer arithmetic: alloc3 has size $WORD, so pointer to $TWO_WORDS bytes starting at offset 0 is out-of-bounds
-   |
-note: inside `ptr::const_ptr::<impl *const usize>::offset`
-  --> $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
-note: inside `_`
-  --> $DIR/ptr_comparisons.rs:50:34
-   |
-LL | const _: *const usize = unsafe { (FOO as *const usize).offset(2) };
-   |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-error[E0080]: evaluation of constant value failed
-  --> $DIR/ptr_comparisons.rs:53:33
-   |
-LL |     unsafe { std::ptr::addr_of!((*(FOO as *const usize as *const [u8; 1000]))[999]) };
-   |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ dereferencing pointer failed: alloc3 has size $WORD, so pointer to 1000 bytes starting at offset 0 is out-of-bounds
-
-error[E0080]: evaluation of constant value failed
-  --> $DIR/ptr_comparisons.rs:57:27
-   |
-LL | const _: usize = unsafe { std::mem::transmute::<*const usize, usize>(FOO) + 4 };
-   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unable to turn pointer into raw bytes
-   |
-   = help: this code performed an operation that depends on the underlying bytes representing a pointer
-   = help: the absolute address of a pointer is not known at compile-time, so such operations are not supported
-
-error[E0080]: evaluation of constant value failed
-  --> $DIR/ptr_comparisons.rs:61:27
-   |
-LL | const _: usize = unsafe { *std::mem::transmute::<&&usize, &usize>(&FOO) + 4 };
-   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unable to turn pointer into raw bytes
-   |
-   = help: this code performed an operation that depends on the underlying bytes representing a pointer
-   = help: the absolute address of a pointer is not known at compile-time, so such operations are not supported
-
-error: aborting due to 4 previous errors
-
-For more information about this error, try `rustc --explain E0080`.