Rollup of 5 pull requests

compiler/rustc_const_eval/src/interpret/intrinsics.rs

@@ -217,7 +217,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                     sym::mul_with_overflow => BinOp::Mul,
                     _ => bug!(),
                 };
-                self.binop_with_overflow(bin_op, &lhs, &rhs, dest)?;
+                self.binop_with_overflow(
+                    bin_op, /*force_overflow_checks*/ true, &lhs, &rhs, dest,
+                )?;
             }
             sym::saturating_add | sym::saturating_sub => {
                 let l = self.read_immediate(&args[0])?;

compiler/rustc_const_eval/src/interpret/machine.rs

@@ -144,6 +144,9 @@ pub trait Machine<'mir, 'tcx>: Sized {
         true
     }
 
+    /// Whether CheckedBinOp MIR statements should actually check for overflow.
+    fn check_binop_checks_overflow(_ecx: &InterpCx<'mir, 'tcx, Self>) -> bool;
+
     /// Entry point for obtaining the MIR of anything that should get evaluated.
     /// So not just functions and shims, but also const/static initializers, anonymous
     /// constants, ...
@@ -468,6 +471,11 @@ pub macro compile_time_machine(<$mir: lifetime, $tcx: lifetime>) {
         true
     }
 
+    #[inline(always)]
+    fn check_binop_checks_overflow(_ecx: &InterpCx<$mir, $tcx, Self>) -> bool {
+        true
+    }
+
     #[inline(always)]
     fn call_extra_fn(
         _ecx: &mut InterpCx<$mir, $tcx, Self>,
@@ -513,7 +521,7 @@ pub macro compile_time_machine(<$mir: lifetime, $tcx: lifetime>) {
         _ecx: &InterpCx<$mir, $tcx, Self>,
         addr: u64,
     ) -> Pointer<Option<AllocId>> {
-        Pointer::new(None, Size::from_bytes(addr))
+        Pointer::from_addr(addr)
     }
 
     #[inline(always)]
@@ -523,7 +531,7 @@ pub macro compile_time_machine(<$mir: lifetime, $tcx: lifetime>) {
     ) -> InterpResult<$tcx, Pointer<Option<AllocId>>> {
         // Allow these casts, but make the pointer not dereferenceable.
         // (I.e., they behave like transmutation.)
-        Ok(Pointer::new(None, Size::from_bytes(addr)))
+        Ok(Pointer::from_addr(addr))
     }
 
     #[inline(always)]

compiler/rustc_const_eval/src/interpret/operator.rs

@@ -12,9 +12,13 @@ use super::{ImmTy, Immediate, InterpCx, Machine, PlaceTy};
 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     /// Applies the binary operation `op` to the two operands and writes a tuple of the result
     /// and a boolean signifying the potential overflow to the destination.
+    ///
+    /// `force_overflow_checks` indicates whether overflow checks should be done even when
+    /// `tcx.sess.overflow_checks()` is `false`.
     pub fn binop_with_overflow(
         &mut self,
         op: mir::BinOp,
+        force_overflow_checks: bool,
         left: &ImmTy<'tcx, M::PointerTag>,
         right: &ImmTy<'tcx, M::PointerTag>,
         dest: &PlaceTy<'tcx, M::PointerTag>,
@@ -26,6 +30,11 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             "type mismatch for result of {:?}",
             op,
         );
+        // As per https://github.com/rust-lang/rust/pull/98738, we always return `false` in the 2nd
+        // component when overflow checking is disabled.
+        let overflowed =
+            overflowed && (force_overflow_checks || M::check_binop_checks_overflow(self));
+        // Write the result to `dest`.
         if let Abi::ScalarPair(..) = dest.layout.abi {
             // We can use the optimized path and avoid `place_field` (which might do
             // `force_allocation`).

compiler/rustc_const_eval/src/interpret/place.rs

@@ -188,7 +188,7 @@ impl<'tcx, Tag: Provenance> MPlaceTy<'tcx, Tag> {
     #[inline]
     pub fn dangling(layout: TyAndLayout<'tcx>) -> Self {
         let align = layout.align.abi;
-        let ptr = Pointer::new(None, Size::from_bytes(align.bytes())); // no provenance, absolute address
+        let ptr = Pointer::from_addr(align.bytes()); // no provenance, absolute address
         // `Poison` this to make sure that the pointer value `ptr` is never observable by the program.
         MPlaceTy { mplace: MemPlace { ptr, meta: MemPlaceMeta::Poison }, layout, align }
     }

compiler/rustc_const_eval/src/interpret/step.rs

@@ -185,7 +185,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 let left = self.read_immediate(&self.eval_operand(left, None)?)?;
                 let layout = binop_right_homogeneous(bin_op).then_some(left.layout);
                 let right = self.read_immediate(&self.eval_operand(right, layout)?)?;
-                self.binop_with_overflow(bin_op, &left, &right, &dest)?;
+                self.binop_with_overflow(
+                    bin_op, /*force_overflow_checks*/ false, &left, &right, &dest,
+                )?;
             }
 
             UnaryOp(un_op, ref operand) => {

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

@@ -186,17 +186,17 @@ pub enum CheckInAllocMsg {
 
 impl fmt::Display for CheckInAllocMsg {
     /// When this is printed as an error the context looks like this:
-    /// "{msg}0x01 is not a valid pointer".
+    /// "{msg}{pointer} is a dangling pointer".
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(
             f,
             "{}",
             match *self {
                 CheckInAllocMsg::DerefTest => "dereferencing pointer failed: ",
                 CheckInAllocMsg::MemoryAccessTest => "memory access failed: ",
-                CheckInAllocMsg::PointerArithmeticTest => "pointer arithmetic failed: ",
+                CheckInAllocMsg::PointerArithmeticTest => "out-of-bounds pointer arithmetic: ",
                 CheckInAllocMsg::OffsetFromTest => "out-of-bounds offset_from: ",
-                CheckInAllocMsg::InboundsTest => "",
+                CheckInAllocMsg::InboundsTest => "out-of-bounds pointer use: ",
             }
         )
     }
@@ -350,14 +350,12 @@ impl fmt::Display for UndefinedBehaviorInfo<'_> {
                 ptr_size = ptr_size.bytes(),
                 ptr_size_p = pluralize!(ptr_size.bytes()),
             ),
-            DanglingIntPointer(0, CheckInAllocMsg::InboundsTest) => {
-                write!(f, "null pointer is not a valid pointer for this operation")
-            }
-            DanglingIntPointer(0, msg) => {
-                write!(f, "{msg}null pointer is not a valid pointer")
-            }
             DanglingIntPointer(i, msg) => {
-                write!(f, "{msg}{i:#x} is not a valid pointer")
+                write!(
+                    f,
+                    "{msg}{pointer} is a dangling pointer (it has no provenance)",
+                    pointer = Pointer::<Option<AllocId>>::from_addr(*i),
+                )
             }
             AlignmentCheckFailed { required, has } => write!(
                 f,

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

@@ -181,7 +181,17 @@ impl<Tag: Provenance> fmt::Debug for Pointer<Option<Tag>> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self.provenance {
             Some(tag) => Provenance::fmt(&Pointer::new(tag, self.offset), f),
-            None => write!(f, "{:#x}", self.offset.bytes()),
+            None => write!(f, "{:#x}[noalloc]", self.offset.bytes()),
+        }
+    }
+}
+
+impl<Tag: Provenance> fmt::Display for Pointer<Option<Tag>> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if self.provenance.is_none() && self.offset.bytes() == 0 {
+            write!(f, "null pointer")
+        } else {
+            fmt::Debug::fmt(self, f)
         }
     }
 }
@@ -226,9 +236,14 @@ impl<Tag> Pointer<Option<Tag>> {
 }
 
 impl<Tag> Pointer<Option<Tag>> {
+    #[inline(always)]
+    pub fn from_addr(addr: u64) -> Self {
+        Pointer { provenance: None, offset: Size::from_bytes(addr) }
+    }
+
     #[inline(always)]
     pub fn null() -> Self {
-        Pointer { provenance: None, offset: Size::ZERO }
+        Pointer::from_addr(0)
     }
 }
 

compiler/rustc_middle/src/mir/syntax.rs

@@ -993,8 +993,9 @@ pub enum Rvalue<'tcx> {
 
     /// Same as `BinaryOp`, but yields `(T, bool)` with a `bool` indicating an error condition.
     ///
-    /// When overflow checking is disabled, the error condition is false. Otherwise, the error
-    /// condition is determined as described below.
+    /// When overflow checking is disabled and we are generating run-time code, the error condition
+    /// is false. Otherwise, and always during CTFE, the error condition is determined as described
+    /// below.
     ///
     /// For addition, subtraction, and multiplication on integers the error condition is set when
     /// the infinite precision result would be unequal to the actual result.

src/bootstrap/bootstrap.py

@@ -152,6 +152,10 @@ def run(args, verbose=False, exception=False, is_bootstrap=False, **kwargs):
     if verbose:
         print("running: " + ' '.join(args))
     sys.stdout.flush()
+    # Ensure that the .exe is used on Windows just in case a Linux ELF has been
+    # compiled in the same directory.
+    if os.name == 'nt' and not args[0].endswith('.exe'):
+        args[0] += '.exe'
     # Use Popen here instead of call() as it apparently allows powershell on
     # Windows to not lock up waiting for input presumably.
     ret = subprocess.Popen(args, **kwargs)

src/test/codegen/issue-37945.rs

@@ -17,7 +17,9 @@ pub fn is_empty_1(xs: Iter<f32>) -> bool {
 // CHECK-NEXT:  start:
 // CHECK-NEXT:    [[A:%.*]] = icmp ne {{i32\*|ptr}} %xs.1, null
 // CHECK-NEXT:    tail call void @llvm.assume(i1 [[A]])
-// CHECK-NEXT:    [[B:%.*]] = icmp eq {{i32\*|ptr}} %xs.1, %xs.0
+// The order between %xs.0 and %xs.1 on the next line doesn't matter
+// and different LLVM versions produce different order.
+// CHECK-NEXT:    [[B:%.*]] = icmp eq {{i32\*|ptr}} {{%xs.0, %xs.1|%xs.1, %xs.0}}
 // CHECK-NEXT:    ret i1 [[B:%.*]]
     {xs}.next().is_none()
 }
@@ -28,7 +30,9 @@ pub fn is_empty_2(xs: Iter<f32>) -> bool {
 // CHECK-NEXT:  start:
 // CHECK-NEXT:    [[C:%.*]] = icmp ne {{i32\*|ptr}} %xs.1, null
 // CHECK-NEXT:    tail call void @llvm.assume(i1 [[C]])
-// CHECK-NEXT:    [[D:%.*]] = icmp eq {{i32\*|ptr}} %xs.1, %xs.0
+// The order between %xs.0 and %xs.1 on the next line doesn't matter
+// and different LLVM versions produce different order.
+// CHECK-NEXT:    [[D:%.*]] = icmp eq {{i32\*|ptr}} {{%xs.0, %xs.1|%xs.1, %xs.0}}
 // CHECK-NEXT:    ret i1 [[D:%.*]]
     xs.map(|&x| x).next().is_none()
 }

src/test/rustdoc-ui/issue-79467.rs

@@ -0,0 +1,8 @@
+fn g()
+where
+    'static: 'static,
+    dyn 'static: 'static + Copy, //~ ERROR at least one trait is required for an object type
+{
+}
+
+fn main() {}

src/test/rustdoc-ui/issue-79467.stderr

@@ -0,0 +1,9 @@
+error[E0224]: at least one trait is required for an object type
+  --> $DIR/issue-79467.rs:4:5
+   |
+LL |     dyn 'static: 'static + Copy,
+   |     ^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0224`.

src/test/ui/const-ptr/forbidden_slices.32bit.stderr

@@ -4,7 +4,7 @@ error[E0080]: could not evaluate static initializer
 LL |         &*ptr::slice_from_raw_parts(data, len)
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |         |
-   |         dereferencing pointer failed: null pointer is not a valid pointer
+   |         dereferencing pointer failed: null pointer is a dangling pointer (it has no provenance)
    |         inside `std::slice::from_raw_parts::<u32>` at $SRC_DIR/core/src/slice/raw.rs:LL:COL
    |
   ::: $DIR/forbidden_slices.rs:19:34
@@ -18,7 +18,7 @@ error[E0080]: could not evaluate static initializer
 LL |         &*ptr::slice_from_raw_parts(data, len)
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |         |
-   |         dereferencing pointer failed: null pointer is not a valid pointer
+   |         dereferencing pointer failed: null pointer is a dangling pointer (it has no provenance)
    |         inside `std::slice::from_raw_parts::<()>` at $SRC_DIR/core/src/slice/raw.rs:LL:COL
    |
   ::: $DIR/forbidden_slices.rs:20:33
@@ -104,7 +104,7 @@ error[E0080]: could not evaluate static initializer
 LL |         unsafe { intrinsics::ptr_offset_from_unsigned(self, origin) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |                  |
-   |                  out-of-bounds offset_from: null pointer is not a valid pointer
+   |                  out-of-bounds offset_from: null pointer is a dangling pointer (it has no provenance)
    |                  inside `ptr::const_ptr::<impl *const u32>::sub_ptr` at $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
    |
   ::: $SRC_DIR/core/src/slice/raw.rs:LL:COL
@@ -144,7 +144,7 @@ error[E0080]: could not evaluate static initializer
 LL |         unsafe { intrinsics::offset(self, count) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |                  |
-   |                  pointer arithmetic failed: ALLOC_ID has size 4, so pointer to 8 bytes starting at offset 0 is out-of-bounds
+   |                  out-of-bounds pointer arithmetic: ALLOC_ID has size 4, so pointer to 8 bytes starting at offset 0 is out-of-bounds
    |                  inside `ptr::const_ptr::<impl *const u32>::offset` at $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
 ...
 LL |         unsafe { self.offset(count as isize) }
@@ -205,7 +205,7 @@ error[E0080]: could not evaluate static initializer
 LL |         unsafe { intrinsics::offset(self, count) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |                  |
-   |                  pointer arithmetic failed: ALLOC_ID has size 8, so pointer to 8 bytes starting at offset 1 is out-of-bounds
+   |                  out-of-bounds pointer arithmetic: ALLOC_ID has size 8, so pointer to 8 bytes starting at offset 1 is out-of-bounds
    |                  inside `ptr::const_ptr::<impl *const u64>::offset` at $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
 ...
 LL |         unsafe { self.offset(count as isize) }

src/test/ui/const-ptr/forbidden_slices.64bit.stderr

@@ -4,7 +4,7 @@ error[E0080]: could not evaluate static initializer
 LL |         &*ptr::slice_from_raw_parts(data, len)
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |         |
-   |         dereferencing pointer failed: null pointer is not a valid pointer
+   |         dereferencing pointer failed: null pointer is a dangling pointer (it has no provenance)
    |         inside `std::slice::from_raw_parts::<u32>` at $SRC_DIR/core/src/slice/raw.rs:LL:COL
    |
   ::: $DIR/forbidden_slices.rs:19:34
@@ -18,7 +18,7 @@ error[E0080]: could not evaluate static initializer
 LL |         &*ptr::slice_from_raw_parts(data, len)
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |         |
-   |         dereferencing pointer failed: null pointer is not a valid pointer
+   |         dereferencing pointer failed: null pointer is a dangling pointer (it has no provenance)
    |         inside `std::slice::from_raw_parts::<()>` at $SRC_DIR/core/src/slice/raw.rs:LL:COL
    |
   ::: $DIR/forbidden_slices.rs:20:33
@@ -104,7 +104,7 @@ error[E0080]: could not evaluate static initializer
 LL |         unsafe { intrinsics::ptr_offset_from_unsigned(self, origin) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |                  |
-   |                  out-of-bounds offset_from: null pointer is not a valid pointer
+   |                  out-of-bounds offset_from: null pointer is a dangling pointer (it has no provenance)
    |                  inside `ptr::const_ptr::<impl *const u32>::sub_ptr` at $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
    |
   ::: $SRC_DIR/core/src/slice/raw.rs:LL:COL
@@ -144,7 +144,7 @@ error[E0080]: could not evaluate static initializer
 LL |         unsafe { intrinsics::offset(self, count) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |                  |
-   |                  pointer arithmetic failed: ALLOC_ID has size 4, so pointer to 8 bytes starting at offset 0 is out-of-bounds
+   |                  out-of-bounds pointer arithmetic: ALLOC_ID has size 4, so pointer to 8 bytes starting at offset 0 is out-of-bounds
    |                  inside `ptr::const_ptr::<impl *const u32>::offset` at $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
 ...
 LL |         unsafe { self.offset(count as isize) }
@@ -205,7 +205,7 @@ error[E0080]: could not evaluate static initializer
 LL |         unsafe { intrinsics::offset(self, count) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |                  |
-   |                  pointer arithmetic failed: ALLOC_ID has size 8, so pointer to 8 bytes starting at offset 1 is out-of-bounds
+   |                  out-of-bounds pointer arithmetic: ALLOC_ID has size 8, so pointer to 8 bytes starting at offset 1 is out-of-bounds
    |                  inside `ptr::const_ptr::<impl *const u64>::offset` at $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
 ...
 LL |         unsafe { self.offset(count as isize) }

src/test/ui/consts/const-deref-ptr.stderr

@@ -2,7 +2,7 @@ error[E0080]: could not evaluate static initializer
   --> $DIR/const-deref-ptr.rs:4:29
    |
 LL |     static C: u64 = unsafe {*(0xdeadbeef as *const u64)};
-   |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^ dereferencing pointer failed: 0xdeadbeef is not a valid pointer
+   |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^ dereferencing pointer failed: 0xdeadbeef[noalloc] is a dangling pointer (it has no provenance)
 
 error: aborting due to previous error
 

src/test/ui/consts/const-eval/const_raw_ptr_ops2.rs

@@ -5,6 +5,6 @@ const Z: i32 = unsafe { *(&1 as *const i32) };
 
 // bad, will thus error in miri
 const Z2: i32 = unsafe { *(42 as *const i32) }; //~ ERROR evaluation of constant value failed
-//~| is not a valid pointer
+//~| is a dangling pointer
 const Z3: i32 = unsafe { *(44 as *const i32) }; //~ ERROR evaluation of constant value failed
-//~| is not a valid pointer
+//~| is a dangling pointer

src/test/ui/consts/const-eval/const_raw_ptr_ops2.stderr

@@ -2,13 +2,13 @@ error[E0080]: evaluation of constant value failed
   --> $DIR/const_raw_ptr_ops2.rs:7:26
    |
 LL | const Z2: i32 = unsafe { *(42 as *const i32) };
-   |                          ^^^^^^^^^^^^^^^^^^^ dereferencing pointer failed: 0x2a is not a valid pointer
+   |                          ^^^^^^^^^^^^^^^^^^^ dereferencing pointer failed: 0x2a[noalloc] is a dangling pointer (it has no provenance)
 
 error[E0080]: evaluation of constant value failed
   --> $DIR/const_raw_ptr_ops2.rs:9:26
    |
 LL | const Z3: i32 = unsafe { *(44 as *const i32) };
-   |                          ^^^^^^^^^^^^^^^^^^^ dereferencing pointer failed: 0x2c is not a valid pointer
+   |                          ^^^^^^^^^^^^^^^^^^^ dereferencing pointer failed: 0x2c[noalloc] is a dangling pointer (it has no provenance)
 
 error: aborting due to 2 previous errors
 

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

@@ -319,7 +319,7 @@ error[E0080]: could not evaluate static initializer
   --> $DIR/ub-wide-ptr.rs:147:5
    |
 LL |     mem::transmute::<_, &dyn Trait>((&92u8, 0usize))
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: null pointer is not a valid pointer
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: null pointer is a dangling pointer (it has no provenance)
 
 error[E0080]: could not evaluate static initializer
   --> $DIR/ub-wide-ptr.rs:151:5

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

@@ -319,7 +319,7 @@ error[E0080]: could not evaluate static initializer
   --> $DIR/ub-wide-ptr.rs:147:5
    |
 LL |     mem::transmute::<_, &dyn Trait>((&92u8, 0usize))
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: null pointer is not a valid pointer
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: null pointer is a dangling pointer (it has no provenance)
 
 error[E0080]: could not evaluate static initializer
   --> $DIR/ub-wide-ptr.rs:151:5

src/test/ui/consts/const-mut-refs/mut_ref_in_final_dynamic_check.rs

@@ -11,7 +11,7 @@ const fn helper() -> Option<&'static mut i32> { unsafe {
     // Undefined behaviour (integer as pointer), who doesn't love tests like this.
     // This code never gets executed, because the static checks fail before that.
     Some(&mut *(42 as *mut i32)) //~ ERROR evaluation of constant value failed
-    //~| 0x2a is not a valid pointer
+    //~| 0x2a[noalloc] is a dangling pointer
 } }
 // The error is an evaluation error and not a validation error, so the error is reported
 // directly at the site where it occurs.

src/test/ui/consts/const-mut-refs/mut_ref_in_final_dynamic_check.stderr

@@ -4,7 +4,7 @@ error[E0080]: evaluation of constant value failed
 LL |     Some(&mut *(42 as *mut i32))
    |          ^^^^^^^^^^^^^^^^^^^^^^
    |          |
-   |          dereferencing pointer failed: 0x2a is not a valid pointer
+   |          dereferencing pointer failed: 0x2a[noalloc] is a dangling pointer (it has no provenance)
    |          inside `helper` at $DIR/mut_ref_in_final_dynamic_check.rs:13:10
 ...
 LL | const A: Option<&mut i32> = helper();