tweak pointer out-of-bounds error message

Author: RalfJung

compiler/rustc_middle/src/mir/interpret/error.rs

@@ -181,8 +181,8 @@ pub enum CheckInAllocMsg {
 }
 
 impl fmt::Display for CheckInAllocMsg {
-    /// When this is printed as an error the context looks like this
-    /// "{msg}pointer must be in-bounds at offset..."
+    /// When this is printed as an error the context looks like this:
+    /// "{msg}0x01 is not a valid pointer".
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(
             f,
@@ -318,14 +318,24 @@ impl fmt::Display for UndefinedBehaviorInfo<'_> {
             PointerUseAfterFree(a) => {
                 write!(f, "pointer to {} was dereferenced after this allocation got freed", a)
             }
+            PointerOutOfBounds { alloc_id, offset, size: Size::ZERO, msg, allocation_size } => {
+                write!(
+                    f,
+                    "{}{} has size {}, so pointer at offset {} is out-of-bounds",
+                    msg,
+                    alloc_id,
+                    allocation_size.bytes(),
+                    offset.bytes(),
+                )
+            }
             PointerOutOfBounds { alloc_id, offset, size, msg, allocation_size } => write!(
                 f,
-                "{}pointer must be in-bounds for {} bytes at offset {}, but {} has size {}",
+                "{}{} has size {}, so pointer to {} bytes starting at offset {} is out-of-bounds",
                 msg,
+                alloc_id,
+                allocation_size.bytes(),
                 size.bytes(),
                 offset.bytes(),
-                alloc_id,
-                allocation_size.bytes()
             ),
             DanglingIntPointer(0, CheckInAllocMsg::InboundsTest) => {
                 write!(f, "null pointer is not a valid pointer for this operation")

src/test/ui/const-ptr/out_of_bounds_read.stderr

@@ -4,7 +4,7 @@ error[E0080]: evaluation of constant value failed
 LL |     unsafe { copy_nonoverlapping(src, dst, count) }
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |              |
-   |              memory access failed: pointer must be in-bounds for 4 bytes at offset 4, but alloc7 has size 4
+   |              memory access failed: alloc7 has size 4, so pointer to 4 bytes starting at offset 4 is out-of-bounds
    |              inside `copy_nonoverlapping::<u32>` at $SRC_DIR/core/src/intrinsics.rs:LL:COL
    | 
   ::: $SRC_DIR/core/src/ptr/mod.rs:LL:COL
@@ -23,7 +23,7 @@ error[E0080]: evaluation of constant value failed
 LL |     unsafe { copy_nonoverlapping(src, dst, count) }
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |              |
-   |              memory access failed: pointer must be in-bounds for 4 bytes at offset 4, but alloc7 has size 4
+   |              memory access failed: alloc7 has size 4, so pointer to 4 bytes starting at offset 4 is out-of-bounds
    |              inside `copy_nonoverlapping::<u32>` at $SRC_DIR/core/src/intrinsics.rs:LL:COL
    | 
   ::: $SRC_DIR/core/src/ptr/mod.rs:LL:COL
@@ -47,7 +47,7 @@ error[E0080]: evaluation of constant value failed
 LL |     unsafe { copy_nonoverlapping(src, dst, count) }
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |              |
-   |              memory access failed: pointer must be in-bounds for 4 bytes at offset 4, but alloc7 has size 4
+   |              memory access failed: alloc7 has size 4, so pointer to 4 bytes starting at offset 4 is out-of-bounds
    |              inside `copy_nonoverlapping::<u32>` at $SRC_DIR/core/src/intrinsics.rs:LL:COL
    | 
   ::: $SRC_DIR/core/src/ptr/mod.rs:LL:COL

src/test/ui/consts/const-eval/ub-nonnull.32bit.stderr

@@ -13,7 +13,7 @@ error[E0080]: evaluation of constant value failed
   --> $DIR/ub-nonnull.rs:19:30
    |
 LL |     let out_of_bounds_ptr = &ptr[255];
-   |                              ^^^^^^^^ dereferencing pointer failed: pointer must be in-bounds for 256 bytes at offset 0, but alloc11 has size 1
+   |                              ^^^^^^^^ dereferencing pointer failed: alloc11 has size 1, so pointer to 256 bytes starting at offset 0 is out-of-bounds
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-nonnull.rs:23:1

src/test/ui/consts/const-eval/ub-nonnull.64bit.stderr

@@ -13,7 +13,7 @@ error[E0080]: evaluation of constant value failed
   --> $DIR/ub-nonnull.rs:19:30
    |
 LL |     let out_of_bounds_ptr = &ptr[255];
-   |                              ^^^^^^^^ dereferencing pointer failed: pointer must be in-bounds for 256 bytes at offset 0, but alloc11 has size 1
+   |                              ^^^^^^^^ dereferencing pointer failed: alloc11 has size 1, so pointer to 256 bytes starting at offset 0 is out-of-bounds
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-nonnull.rs:23:1

src/test/ui/consts/const-eval/ub-wide-ptr.32bit.stderr

@@ -302,7 +302,7 @@ error[E0080]: could not evaluate static initializer
   --> $DIR/ub-wide-ptr.rs:139:5
    |
 LL |     mem::transmute::<_, &dyn Trait>((&92u8, &3u64))
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: pointer must be in-bounds for 12 bytes at offset N, but allocN has size N
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: allocN has size N, so pointer to 12 bytes starting at offset N is out-of-bounds
 
 error: aborting due to 28 previous errors
 

src/test/ui/consts/const-eval/ub-wide-ptr.64bit.stderr

@@ -302,7 +302,7 @@ error[E0080]: could not evaluate static initializer
   --> $DIR/ub-wide-ptr.rs:139:5
    |
 LL |     mem::transmute::<_, &dyn Trait>((&92u8, &3u64))
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: pointer must be in-bounds for 24 bytes at offset N, but allocN has size N
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: allocN has size N, so pointer to 24 bytes starting at offset N is out-of-bounds
 
 error: aborting due to 28 previous errors
 

src/test/ui/consts/copy-intrinsic.rs

@@ -24,20 +24,21 @@ const COPY_OOB_1: () = unsafe {
     let mut x = 0i32;
     let dangle = (&mut x as *mut i32).wrapping_add(10);
     // Even if the first ptr is an int ptr and this is a ZST copy, we should detect dangling 2nd ptrs.
-    copy_nonoverlapping(0x100 as *const i32, dangle, 0); //~ evaluation of constant value failed [E0080]
+    copy_nonoverlapping(0x100 as *const i32, dangle, 0); //~ ERROR evaluation of constant value failed [E0080]
+    //~| pointer at offset 40 is out-of-bounds
 };
 const COPY_OOB_2: () = unsafe {
     let x = 0i32;
     let dangle = (&x as *const i32).wrapping_add(10);
     // Even if the second ptr is an int ptr and this is a ZST copy, we should detect dangling 1st ptrs.
-    copy_nonoverlapping(dangle, 0x100 as *mut i32, 0); //~ evaluation of constant value failed [E0080]
-    //~| memory access failed: pointer must be in-bounds
+    copy_nonoverlapping(dangle, 0x100 as *mut i32, 0); //~ ERROR evaluation of constant value failed [E0080]
+    //~| pointer at offset 40 is out-of-bounds
 };
 
 const COPY_SIZE_OVERFLOW: () = unsafe {
     let x = 0;
     let mut y = 0;
-    copy(&x, &mut y, 1usize << (mem::size_of::<usize>() * 8 - 1)); //~ evaluation of constant value failed [E0080]
+    copy(&x, &mut y, 1usize << (mem::size_of::<usize>() * 8 - 1)); //~ ERROR evaluation of constant value failed [E0080]
     //~| overflow computing total size of `copy`
 };
 const COPY_NONOVERLAPPING_SIZE_OVERFLOW: () = unsafe {

src/test/ui/consts/copy-intrinsic.stderr

@@ -2,22 +2,22 @@ error[E0080]: evaluation of constant value failed
   --> $DIR/copy-intrinsic.rs:27:5
    |
 LL |     copy_nonoverlapping(0x100 as *const i32, dangle, 0);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: pointer must be in-bounds for 0 bytes at offset 40, but alloc5 has size 4
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: alloc5 has size 4, so pointer at offset 40 is out-of-bounds
 
 error[E0080]: evaluation of constant value failed
-  --> $DIR/copy-intrinsic.rs:33:5
+  --> $DIR/copy-intrinsic.rs:34:5
    |
 LL |     copy_nonoverlapping(dangle, 0x100 as *mut i32, 0);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: pointer must be in-bounds for 0 bytes at offset 40, but alloc7 has size 4
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: alloc7 has size 4, so pointer at offset 40 is out-of-bounds
 
 error[E0080]: evaluation of constant value failed
-  --> $DIR/copy-intrinsic.rs:40:5
+  --> $DIR/copy-intrinsic.rs:41:5
    |
 LL |     copy(&x, &mut y, 1usize << (mem::size_of::<usize>() * 8 - 1));
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overflow computing total size of `copy`
 
 error[E0080]: evaluation of constant value failed
-  --> $DIR/copy-intrinsic.rs:46:5
+  --> $DIR/copy-intrinsic.rs:47:5
    |
 LL |     copy_nonoverlapping(&x, &mut y, 1usize << (mem::size_of::<usize>() * 8 - 1));
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overflow computing total size of `copy_nonoverlapping`

src/test/ui/consts/offset_ub.stderr

@@ -18,7 +18,7 @@ error[E0080]: evaluation of constant value failed
 LL |         unsafe { intrinsics::offset(self, count) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |                  |
-   |                  pointer arithmetic failed: pointer must be in-bounds for 2 bytes at offset 0, but allocN has size 1
+   |                  pointer arithmetic failed: allocN has size 1, so pointer to 2 bytes 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:9:43
@@ -32,7 +32,7 @@ error[E0080]: evaluation of constant value failed
 LL |         unsafe { intrinsics::offset(self, count) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |                  |
-   |                  pointer arithmetic failed: pointer must be in-bounds for 101 bytes at offset 0, but allocN has size 100
+   |                  pointer arithmetic failed: allocN has size 100, so pointer to 101 bytes 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:10:45
@@ -102,7 +102,7 @@ error[E0080]: evaluation of constant value failed
 LL |         unsafe { intrinsics::offset(self, count) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |                  |
-   |                  pointer arithmetic failed: pointer must be in-bounds for 1 bytes at offset 0, but allocN has size 0
+   |                  pointer arithmetic failed: allocN has size 0, so pointer to 1 bytes 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:17:50

src/test/ui/consts/ptr_comparisons.rs

@@ -63,7 +63,7 @@ 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
-//~| pointer must be in-bounds
+//~| out-of-bounds
 
 const _: usize = unsafe { std::mem::transmute::<*const usize, usize>(FOO) + 4 };
 //~^ ERROR any use of this value will cause an error