Rollup merge of #84972 - RalfJung:null-ptr-msg, r=oli-obk

CTFE inbounds-error-messages tweak

* use CheckInAllocMsg::PointerArithmeticTest for ptr_offset error
* nicer errors for some null pointer cases

r? `@oli-obk`

Author: JohnTitor

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

@@ -306,6 +306,9 @@ impl fmt::Display for UndefinedBehaviorInfo<'_> {
                 ptr.alloc_id,
                 allocation_size.bytes()
             ),
+            DanglingIntPointer(_, CheckInAllocMsg::InboundsTest) => {
+                write!(f, "null pointer is not allowed for this operation")
+            }
             DanglingIntPointer(i, msg) => {
                 write!(f, "{} failed: 0x{:x} is not a valid pointer", msg, i)
             }

compiler/rustc_mir/src/interpret/intrinsics.rs

@@ -526,7 +526,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             min_ptr,
             Size::from_bytes(size),
             None,
-            CheckInAllocMsg::InboundsTest,
+            CheckInAllocMsg::PointerArithmeticTest,
         )?;
         Ok(offset_ptr)
     }

compiler/rustc_mir/src/interpret/machine.rs

@@ -369,6 +369,7 @@ pub trait Machine<'mir, 'tcx>: Sized {
     ) -> InterpResult<'tcx, Pointer<Self::PointerTag>> {
         Err((if int == 0 {
             // This is UB, seriously.
+            // (`DanglingIntPointer` with these exact arguments has special printing code.)
             err_ub!(DanglingIntPointer(0, CheckInAllocMsg::InboundsTest))
         } else {
             // This is just something we cannot support during const-eval.

compiler/rustc_mir/src/interpret/validity.rs

@@ -330,7 +330,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                         vtable,
                         3 * self.ecx.tcx.data_layout.pointer_size, // drop, size, align
                         Some(self.ecx.tcx.data_layout.pointer_align.abi),
-                        CheckInAllocMsg::InboundsTest,
+                        CheckInAllocMsg::InboundsTest, // will anyway be replaced by validity message
                     ),
                     self.path,
                     err_ub!(DanglingIntPointer(..)) |
@@ -416,7 +416,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                 place.ptr,
                 size,
                 Some(align),
-                CheckInAllocMsg::InboundsTest,
+                CheckInAllocMsg::InboundsTest, // will anyway be replaced by validity message
             ),
             self.path,
             err_ub!(AlignmentCheckFailed { required, has }) =>

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

@@ -296,7 +296,7 @@ error[E0080]: could not evaluate static initializer
   --> $DIR/ub-wide-ptr.rs:135:5
    |
 LL |     mem::transmute::<_, &dyn Trait>((&92u8, 0usize))
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ inbounds test failed: 0x0 is not a valid pointer
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ null pointer is not allowed for this operation
 
 error[E0080]: could not evaluate static initializer
   --> $DIR/ub-wide-ptr.rs:139:5

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

@@ -296,7 +296,7 @@ error[E0080]: could not evaluate static initializer
   --> $DIR/ub-wide-ptr.rs:135:5
    |
 LL |     mem::transmute::<_, &dyn Trait>((&92u8, 0usize))
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ inbounds test failed: 0x0 is not a valid pointer
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ null pointer is not allowed for this operation
 
 error[E0080]: could not evaluate static initializer
   --> $DIR/ub-wide-ptr.rs:139:5

src/test/ui/consts/offset_from_ub.stderr

@@ -74,7 +74,7 @@ error: any use of this value will cause an error
 LL |           unsafe { intrinsics::ptr_offset_from(self, origin) }
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |                    |
-   |                    inbounds test failed: 0x0 is not a valid pointer
+   |                    null pointer is not allowed for this operation
    |                    inside `ptr::const_ptr::<impl *const u8>::offset_from` at $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
    |                    inside `OFFSET_FROM_NULL` at $DIR/offset_from_ub.rs:36:14
    | 

src/test/ui/consts/offset_ub.stderr

@@ -23,7 +23,7 @@ error: any use of this value will cause an error
 LL |         unsafe { intrinsics::offset(self, count) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |                  |
-   |                  inbounds test failed: pointer must be in-bounds at offset 2, but is outside bounds of allocN which has size 1
+   |                  pointer arithmetic failed: pointer must be in-bounds at offset 2, but is outside bounds of allocN which has size 1
    |                  inside `ptr::const_ptr::<impl *const u8>::offset` at $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
    |                  inside `AFTER_END` at $DIR/offset_ub.rs:7:43
    | 
@@ -41,7 +41,7 @@ error: any use of this value will cause an error
 LL |         unsafe { intrinsics::offset(self, count) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |                  |
-   |                  inbounds test failed: pointer must be in-bounds at offset 101, but is outside bounds of allocN which has size 100
+   |                  pointer arithmetic failed: pointer must be in-bounds at offset 101, but is outside bounds of allocN which has size 100
    |                  inside `ptr::const_ptr::<impl *const u8>::offset` at $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
    |                  inside `AFTER_ARRAY` at $DIR/offset_ub.rs:8:45
    | 
@@ -131,7 +131,7 @@ error: any use of this value will cause an error
 LL |         unsafe { intrinsics::offset(self, count) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |                  |
-   |                  inbounds test failed: pointer must be in-bounds at offset 1, but is outside bounds of allocN which has size 0
+   |                  pointer arithmetic failed: pointer must be in-bounds at offset 1, but is outside bounds of allocN which has size 0
    |                  inside `ptr::const_ptr::<impl *const u8>::offset` at $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
    |                  inside `ZERO_SIZED_ALLOC` at $DIR/offset_ub.rs:15:50
    | 
@@ -167,7 +167,7 @@ error: any use of this value will cause an error
 LL |         unsafe { intrinsics::offset(self, count) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |                  |
-   |                  inbounds test failed: 0x0 is not a valid pointer
+   |                  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
    |                  inside `NULL_OFFSET_ZERO` at $DIR/offset_ub.rs:19:50
    | 

src/test/ui/consts/ptr_comparisons.stderr

@@ -4,7 +4,7 @@ error: any use of this value will cause an error
 LL |         unsafe { intrinsics::offset(self, count) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |                  |
-   |                  inbounds test failed: pointer must be in-bounds at offset $TWO_WORDS, but is outside bounds of alloc2 which has size $WORD
+   |                  pointer arithmetic failed: pointer must be in-bounds at offset $TWO_WORDS, but is outside bounds of alloc2 which has size $WORD
    |                  inside `ptr::const_ptr::<impl *const usize>::offset` at $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
    |                  inside `_` at $DIR/ptr_comparisons.rs:61:34
    |