Auto merge of #87224 - RalfJung:miri-ptr-oob, r=oli-obk

miri: better ptr-out-of-bounds errors

For offsets larger than `isize::MAX`, display them as negative offsets.

r? `@oli-obk`

2 files changed, 25 insertions, 10 deletions

diff --git a/src/test/ui/consts/offset_ub.rs b/src/test/ui/consts/offset_ub.rs
index a22296a7b00..42a285a6eab 100644
--- a/src/test/ui/consts/offset_ub.rs
+++ b/src/test/ui/consts/offset_ub.rs
@@ -13,6 +13,7 @@ pub const OVERFLOW: *const u16 = unsafe { [0u16; 1].as_ptr().offset(isize::MAX)
 pub const UNDERFLOW: *const u16 = unsafe { [0u16; 1].as_ptr().offset(isize::MIN) }; //~NOTE
 pub const OVERFLOW_ADDRESS_SPACE: *const u8 = unsafe { (usize::MAX as *const u8).offset(2) }; //~NOTE
 pub const UNDERFLOW_ADDRESS_SPACE: *const u8 = unsafe { (1 as *const u8).offset(-2) }; //~NOTE
+pub const NEGATIVE_OFFSET: *const u8 = unsafe { [0u8; 1].as_ptr().wrapping_offset(-2).offset(-2) }; //~NOTE
 
 pub const ZERO_SIZED_ALLOC: *const u8 = unsafe { [0u8; 0].as_ptr().offset(1) }; //~NOTE
 pub const DANGLING: *const u8 = unsafe { ptr::NonNull::<u8>::dangling().as_ptr().offset(4) }; //~NOTE
diff --git a/src/test/ui/consts/offset_ub.stderr b/src/test/ui/consts/offset_ub.stderr
index 4f7c4f92060..66a2722ed4a 100644
--- a/src/test/ui/consts/offset_ub.stderr
+++ b/src/test/ui/consts/offset_ub.stderr
@@ -102,13 +102,27 @@ error[E0080]: evaluation of constant value failed
 LL |         unsafe { intrinsics::offset(self, count) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |                  |
-   |                  pointer arithmetic failed: allocN has size 0, so pointer to 1 bytes starting at offset 0 is out-of-bounds
+   |                  pointer arithmetic failed: allocN has size 1, so pointer to 2 bytes starting at offset -4 is out-of-bounds
    |                  inside `ptr::const_ptr::<impl *const u8>::offset` at $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
    | 
-  ::: $DIR/offset_ub.rs:17:50
+  ::: $DIR/offset_ub.rs:16:49
+   |
+LL | pub const NEGATIVE_OFFSET: *const u8 = unsafe { [0u8; 1].as_ptr().wrapping_offset(-2).offset(-2) };
+   |                                                 ------------------------------------------------ inside `NEGATIVE_OFFSET` at $DIR/offset_ub.rs:16:49
+
+error[E0080]: evaluation of constant value failed
+  --> $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
+   |
+LL |         unsafe { intrinsics::offset(self, count) }
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                  |
+   |                  pointer arithmetic failed: allocN has size 0, so pointer to 1 byte starting at offset 0 is out-of-bounds
+   |                  inside `ptr::const_ptr::<impl *const u8>::offset` at $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
+   | 
+  ::: $DIR/offset_ub.rs:18:50
    |
 LL | pub const ZERO_SIZED_ALLOC: *const u8 = unsafe { [0u8; 0].as_ptr().offset(1) };
-   |                                                  --------------------------- inside `ZERO_SIZED_ALLOC` at $DIR/offset_ub.rs:17:50
+   |                                                  --------------------------- inside `ZERO_SIZED_ALLOC` at $DIR/offset_ub.rs:18:50
 
 error[E0080]: evaluation of constant value failed
   --> $SRC_DIR/core/src/ptr/mut_ptr.rs:LL:COL
@@ -119,10 +133,10 @@ LL |         unsafe { intrinsics::offset(self, count) as *mut T }
    |                  0x1 is not a valid pointer
    |                  inside `ptr::mut_ptr::<impl *mut u8>::offset` at $SRC_DIR/core/src/ptr/mut_ptr.rs:LL:COL
    | 
-  ::: $DIR/offset_ub.rs:18:42
+  ::: $DIR/offset_ub.rs:19:42
    |
 LL | pub const DANGLING: *const u8 = unsafe { ptr::NonNull::<u8>::dangling().as_ptr().offset(4) };
-   |                                          ------------------------------------------------- inside `DANGLING` at $DIR/offset_ub.rs:18:42
+   |                                          ------------------------------------------------- inside `DANGLING` at $DIR/offset_ub.rs:19:42
 
 error[E0080]: evaluation of constant value failed
   --> $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
@@ -133,10 +147,10 @@ LL |         unsafe { intrinsics::offset(self, count) }
    |                  pointer arithmetic failed: 0x0 is not a valid pointer
    |                  inside `ptr::const_ptr::<impl *const u8>::offset` at $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
    | 
-  ::: $DIR/offset_ub.rs:21:50
+  ::: $DIR/offset_ub.rs:22:50
    |
 LL | pub const NULL_OFFSET_ZERO: *const u8 = unsafe { ptr::null::<u8>().offset(0) };
-   |                                                  --------------------------- inside `NULL_OFFSET_ZERO` at $DIR/offset_ub.rs:21:50
+   |                                                  --------------------------- inside `NULL_OFFSET_ZERO` at $DIR/offset_ub.rs:22:50
 
 error[E0080]: evaluation of constant value failed
   --> $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
@@ -147,11 +161,11 @@ LL |         unsafe { intrinsics::offset(self, count) }
    |                  0x7f..f is not a valid pointer
    |                  inside `ptr::const_ptr::<impl *const u8>::offset` at $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
    | 
-  ::: $DIR/offset_ub.rs:24:47
+  ::: $DIR/offset_ub.rs:25:47
    |
 LL | pub const UNDERFLOW_ABS: *const u8 = unsafe { (usize::MAX as *const u8).offset(isize::MIN) };
-   |                                               -------------------------------------------- inside `UNDERFLOW_ABS` at $DIR/offset_ub.rs:24:47
+   |                                               -------------------------------------------- inside `UNDERFLOW_ABS` at $DIR/offset_ub.rs:25:47
 
-error: aborting due to 11 previous errors
+error: aborting due to 12 previous errors
 
 For more information about this error, try `rustc --explain E0080`.