Allow Ptr::offset() to receive any value that can cast to isize (#213)

The rationale behind this change is to avoid unnecessary casts that may
hurt readability, such as: `0_usize as isize`.
With this change, we are allowed to omit the cast, as it will be
performed inside the `offset` function.

This also has the advantage of panicking whenever we try to cast a usize
larger than `isize::MAX`.

Author: FranciscoTGouveia

cpp2rust/converter/models/converter_refcount.cpp

@@ -2084,7 +2084,7 @@ bool ConverterRefCount::ConvertCXXOperatorCallExpr(
       StrCat(
           std::format("{}.as_ref().unwrap()", ConvertRValue(expr->getArg(0))));
       if (isAddrOf()) {
-        StrCat(std::format(".as_pointer().offset(({}) as isize)",
+        StrCat(std::format(".as_pointer().offset(({}))",
                            ConvertRValue(expr->getArg(1))));
       } else {
         if (isRValue()) {
@@ -2104,7 +2104,7 @@ bool ConverterRefCount::ConvertCXXOperatorCallExpr(
 
     if (isLValue()) {
       PushConversionKind push_ck(*this, ConversionKind::Unboxed);
-      pending_deref_.set(std::format("({} as {}).offset({} as isize)",
+      pending_deref_.set(std::format("({} as {}).offset({})",
                                      ConvertObject(expr->getArg(0)),
                                      ConvertPtrType(expr->getArg(0)->getType()),
                                      ConvertRValue(expr->getArg(1))),
@@ -2124,7 +2124,7 @@ bool ConverterRefCount::ConvertCXXOperatorCallExpr(
       }
 
       PushConversionKind push(*this, ConversionKind::Unboxed);
-      StrCat(std::format("({} as {}).offset({} as isize)",
+      StrCat(std::format("({} as {}).offset({})",
                          ConvertObject(expr->getArg(0)),
                          ConvertPtrType(expr->getArg(0)->getType()),
                          ConvertRValue(expr->getArg(1))));
@@ -2175,7 +2175,7 @@ void ConverterRefCount::ConvertArraySubscript(clang::Expr *base,
 
     {
       PushParen paren(*this, is_inner_boxed);
-      StrCat(std::format("({} as {}).offset({} as isize)",
+      StrCat(std::format("({} as {}).offset({})",
                          ToString(base->IgnoreImplicit()),
                          ConvertPtrType(base->IgnoreImplicit()->getType()),
                          ConvertRValue(idx)));

libcc2rs/src/rc.rs

@@ -296,7 +296,11 @@ impl<T> Ptr<T> {
     }
 
     #[inline]
-    pub fn offset(&self, offset: isize) -> Self {
+    pub fn offset(&self, offset: impl TryInto<isize>) -> Self {
+        let offset = offset
+            .try_into()
+            .ok()
+            .expect("the offset must fit in a isize");
         let step = self.elem_step();
         Self {
             kind: self.kind.clone(),

tests/ub/out/refcount/ub7.rs

@@ -26,5 +26,5 @@ fn main_0() -> i32 {
         ('n' as u8),
         ('g' as u8),
     ])));
-    return (({ strlen_0(((s.as_pointer() as Ptr<u8>).offset(0 as isize))) }) as i32);
+    return (({ strlen_0(((s.as_pointer() as Ptr<u8>).offset(0))) }) as i32);
 }

tests/unit/out/refcount/04_address_taken_array.rs

@@ -16,7 +16,7 @@ fn main_0() -> i32 {
     let arr2_ptr: Value<Ptr<i32>> = Rc::new(RefCell::new((arr2.as_pointer() as Ptr<i32>)));
     (*arr2_ptr.borrow()).offset((0) as isize).write(5);
     (*arr2_ptr.borrow()).offset((1) as isize).write(6);
-    let arr2_ref1: Ptr<i32> = (arr2.as_pointer() as Ptr<i32>).offset(1 as isize);
+    let arr2_ref1: Ptr<i32> = (arr2.as_pointer() as Ptr<i32>).offset(1);
     arr2_ref1.write(7);
     return ((*arr2.borrow())[(0) as usize] + (*arr2.borrow())[(1) as usize]);
 }

tests/unit/out/refcount/array_of_noncopy_struct.rs

@@ -36,7 +36,7 @@ fn main_0() -> i32 {
     assert!(((*(*arr.borrow())[(1) as usize].data.borrow()).len() == 1_usize));
     assert!(
         ((((*arr.borrow())[(1) as usize].data.as_pointer() as Ptr<i32>)
-            .offset(0_usize as isize)
+            .offset(0_usize)
             .read())
             == 42)
     );

tests/unit/out/refcount/borrow_mut_opt.rs

@@ -63,7 +63,7 @@ pub fn convert_with_rhs_1() {
     (*x.borrow_mut()) += __rhs;
     let __rhs = ((*p.borrow()).read());
     (*y.borrow_mut()) += __rhs;
-    (*p.borrow_mut()) = ((arr.as_pointer() as Ptr<i32>).offset(0 as isize));
+    (*p.borrow_mut()) = ((arr.as_pointer() as Ptr<i32>).offset(0));
     let __rhs = ((*p.borrow()).read());
     (*arr.borrow_mut())[(0) as usize] = __rhs;
     let __rhs = (*x.borrow());

tests/unit/out/refcount/bounded_struct_ptr.rs

@@ -53,9 +53,7 @@ fn main_0() -> i32 {
         ((*arr.borrow())[(1) as usize].x1.as_pointer()),
     ));
     let a: Value<i32> = Rc::new(RefCell::new(((*p1.borrow()).read())));
-    let p2: Value<Ptr<Foo>> = Rc::new(RefCell::new(
-        ((arr.as_pointer() as Ptr<Foo>).offset(0 as isize)),
-    ));
+    let p2: Value<Ptr<Foo>> = Rc::new(RefCell::new(((arr.as_pointer() as Ptr<Foo>).offset(0))));
     return {
         let _lhs = (*a.borrow());
         _lhs + (*(*(*p2.borrow()).upgrade().deref()).x2.borrow())

tests/unit/out/refcount/char_printing.rs

@@ -21,12 +21,8 @@ fn main_0() -> i32 {
     write!(libcc2rs::cout(), "{:} a", (*i.borrow()),);
     libcc2rs::cout().write_all(
         &([
-            (&[((vec_.as_pointer() as Ptr<u8>)
-                .offset(0_usize as isize)
-                .read())] as &[u8]),
-            (&[((vec_.as_pointer() as Ptr<u8>)
-                .offset(1_usize as isize)
-                .read())] as &[u8]),
+            (&[((vec_.as_pointer() as Ptr<u8>).offset(0_usize).read())] as &[u8]),
+            (&[((vec_.as_pointer() as Ptr<u8>).offset(1_usize).read())] as &[u8]),
             (&[('o' as u8)] as &[u8]),
             (&(*str.borrow())[..(*str.borrow()).len() - 1] as &[u8]),
             (&[b'\n'] as &[u8]),
@@ -46,13 +42,9 @@ fn main_0() -> i32 {
     write!(libcc2rs::cout(), "Hello, World!\n",);
     libcc2rs::cout().write_all(
         &([
-            (&[((vec_.as_pointer() as Ptr<u8>)
-                .offset(0_usize as isize)
-                .read())] as &[u8]),
+            (&[((vec_.as_pointer() as Ptr<u8>).offset(0_usize).read())] as &[u8]),
             (&[('\n' as u8)] as &[u8]),
-            (&[((vec_.as_pointer() as Ptr<u8>)
-                .offset(1_usize as isize)
-                .read())] as &[u8]),
+            (&[((vec_.as_pointer() as Ptr<u8>).offset(1_usize).read())] as &[u8]),
             (&[('\n' as u8)] as &[u8]),
         ]
         .concat()),

tests/unit/out/refcount/char_printing_cerr.rs

@@ -21,12 +21,8 @@ fn main_0() -> i32 {
     write!(libcc2rs::cerr(), "{:} a", (*i.borrow()),);
     libcc2rs::cerr().write_all(
         &([
-            (&[((vec_.as_pointer() as Ptr<u8>)
-                .offset(0_usize as isize)
-                .read())] as &[u8]),
-            (&[((vec_.as_pointer() as Ptr<u8>)
-                .offset(1_usize as isize)
-                .read())] as &[u8]),
+            (&[((vec_.as_pointer() as Ptr<u8>).offset(0_usize).read())] as &[u8]),
+            (&[((vec_.as_pointer() as Ptr<u8>).offset(1_usize).read())] as &[u8]),
             (&[('o' as u8)] as &[u8]),
             (&(*str.borrow())[..(*str.borrow()).len() - 1] as &[u8]),
             (&[b'\n'] as &[u8]),
@@ -46,13 +42,9 @@ fn main_0() -> i32 {
     write!(libcc2rs::cerr(), "Hello, World!\n",);
     libcc2rs::cerr().write_all(
         &([
-            (&[((vec_.as_pointer() as Ptr<u8>)
-                .offset(0_usize as isize)
-                .read())] as &[u8]),
+            (&[((vec_.as_pointer() as Ptr<u8>).offset(0_usize).read())] as &[u8]),
             (&[('\n' as u8)] as &[u8]),
-            (&[((vec_.as_pointer() as Ptr<u8>)
-                .offset(1_usize as isize)
-                .read())] as &[u8]),
+            (&[((vec_.as_pointer() as Ptr<u8>).offset(1_usize).read())] as &[u8]),
             (&[('\n' as u8)] as &[u8]),
         ]
         .concat()),

tests/unit/out/refcount/clone_vs_move.rs

@@ -162,7 +162,7 @@ fn main_0() -> i32 {
     'loop_: while ((*i.borrow()) < (*N.borrow())) {
         assert!(
             (((v2.as_pointer() as Ptr<i32>)
-                .offset(((*i.borrow()) as usize) as isize)
+                .offset(((*i.borrow()) as usize))
                 .read())
                 == (*i.borrow()))
         );
@@ -171,21 +171,21 @@ fn main_0() -> i32 {
     let i: Value<i32> = Rc::new(RefCell::new(0));
     'loop_: while ((*i.borrow()) < (*N.borrow())) {
         (v2.as_pointer() as Ptr<i32>)
-            .offset(((*i.borrow()) as usize) as isize)
+            .offset(((*i.borrow()) as usize))
             .with_mut(|__v| __v.prefix_inc());
         (*i.borrow_mut()).prefix_inc();
     }
     let i: Value<i32> = Rc::new(RefCell::new(0));
     'loop_: while ((*i.borrow()) < (*N.borrow())) {
         assert!(
             (((v2.as_pointer() as Ptr<i32>)
-                .offset(((*i.borrow()) as usize) as isize)
+                .offset(((*i.borrow()) as usize))
                 .read())
                 == ((*i.borrow()) + 1))
         );
         assert!(
             (((v1.as_pointer() as Ptr<i32>)
-                .offset(((*i.borrow()) as usize) as isize)
+                .offset(((*i.borrow()) as usize))
                 .read())
                 == (*i.borrow()))
         );
@@ -216,7 +216,7 @@ fn main_0() -> i32 {
     'loop_: while ((*i.borrow()) < (*N.borrow())) {
         assert!(
             ((*((m1.as_pointer() as Ptr<Value<Vec<i32>>>)
-                .offset(((*i.borrow()) as usize) as isize)
+                .offset(((*i.borrow()) as usize))
                 .upgrade()
                 .deref()
                 .as_pointer() as Ptr<Vec<i32>>)
@@ -227,7 +227,7 @@ fn main_0() -> i32 {
         );
         assert!(
             ((*((m2.as_pointer() as Ptr<Value<Vec<i32>>>)
-                .offset(((*i.borrow()) as usize) as isize)
+                .offset(((*i.borrow()) as usize))
                 .upgrade()
                 .deref()
                 .as_pointer() as Ptr<Vec<i32>>)
@@ -240,21 +240,21 @@ fn main_0() -> i32 {
         'loop_: while ((*j.borrow()) < 10) {
             assert!(
                 ((((m1.as_pointer() as Ptr<Value<Vec<i32>>>)
-                    .offset(((*i.borrow()) as usize) as isize)
+                    .offset(((*i.borrow()) as usize))
                     .upgrade()
                     .deref()
                     .as_pointer() as Ptr<i32>)
-                    .offset(((*j.borrow()) as usize) as isize)
+                    .offset(((*j.borrow()) as usize))
                     .read())
                     == 0)
             );
             assert!(
                 ((((m2.as_pointer() as Ptr<Value<Vec<i32>>>)
-                    .offset(((*i.borrow()) as usize) as isize)
+                    .offset(((*i.borrow()) as usize))
                     .upgrade()
                     .deref()
                     .as_pointer() as Ptr<i32>)
-                    .offset(((*j.borrow()) as usize) as isize)
+                    .offset(((*j.borrow()) as usize))
                     .read())
                     == 0)
             );
@@ -267,11 +267,11 @@ fn main_0() -> i32 {
         let j: Value<i32> = Rc::new(RefCell::new(0));
         'loop_: while ((*j.borrow()) < 10) {
             ((m2.as_pointer() as Ptr<Value<Vec<i32>>>)
-                .offset(((*i.borrow()) as usize) as isize)
+                .offset(((*i.borrow()) as usize))
                 .upgrade()
                 .deref()
                 .as_pointer() as Ptr<i32>)
-                .offset(((*j.borrow()) as usize) as isize)
+                .offset(((*j.borrow()) as usize))
                 .with_mut(|__v| __v.postfix_inc());
             (*j.borrow_mut()).prefix_inc();
         }
@@ -281,7 +281,7 @@ fn main_0() -> i32 {
     'loop_: while ((*i.borrow()) < (*N.borrow())) {
         assert!(
             ((*((m1.as_pointer() as Ptr<Value<Vec<i32>>>)
-                .offset(((*i.borrow()) as usize) as isize)
+                .offset(((*i.borrow()) as usize))
                 .upgrade()
                 .deref()
                 .as_pointer() as Ptr<Vec<i32>>)
@@ -292,7 +292,7 @@ fn main_0() -> i32 {
         );
         assert!(
             ((*((m2.as_pointer() as Ptr<Value<Vec<i32>>>)
-                .offset(((*i.borrow()) as usize) as isize)
+                .offset(((*i.borrow()) as usize))
                 .upgrade()
                 .deref()
                 .as_pointer() as Ptr<Vec<i32>>)
@@ -305,21 +305,21 @@ fn main_0() -> i32 {
         'loop_: while ((*j.borrow()) < 10) {
             assert!(
                 ((((m1.as_pointer() as Ptr<Value<Vec<i32>>>)
-                    .offset(((*i.borrow()) as usize) as isize)
+                    .offset(((*i.borrow()) as usize))
                     .upgrade()
                     .deref()
                     .as_pointer() as Ptr<i32>)
-                    .offset(((*j.borrow()) as usize) as isize)
+                    .offset(((*j.borrow()) as usize))
                     .read())
                     == 0)
             );
             assert!(
                 ((((m2.as_pointer() as Ptr<Value<Vec<i32>>>)
-                    .offset(((*i.borrow()) as usize) as isize)
+                    .offset(((*i.borrow()) as usize))
                     .upgrade()
                     .deref()
                     .as_pointer() as Ptr<i32>)
-                    .offset(((*j.borrow()) as usize) as isize)
+                    .offset(((*j.borrow()) as usize))
                     .read())
                     == 1)
             );
@@ -436,37 +436,31 @@ fn main_0() -> i32 {
     ));
     let s2: Value<Vec<u8>> = Rc::new(RefCell::new((*s1.borrow()).clone()));
     (s2.as_pointer() as Ptr<u8>)
-        .offset(0_usize as isize)
+        .offset(0_usize)
         .write(('b' as u8));
     (s2.as_pointer() as Ptr<u8>)
-        .offset(1_usize as isize)
+        .offset(1_usize)
         .write(('b' as u8));
     (s2.as_pointer() as Ptr<u8>)
-        .offset(2_usize as isize)
+        .offset(2_usize)
         .write(('b' as u8));
     assert!(
-        ((((s2.as_pointer() as Ptr<u8>).offset(0_usize as isize).read()) as i32)
-            == (('b' as u8) as i32))
+        ((((s2.as_pointer() as Ptr<u8>).offset(0_usize).read()) as i32) == (('b' as u8) as i32))
     );
     assert!(
-        ((((s2.as_pointer() as Ptr<u8>).offset(1_usize as isize).read()) as i32)
-            == (('b' as u8) as i32))
+        ((((s2.as_pointer() as Ptr<u8>).offset(1_usize).read()) as i32) == (('b' as u8) as i32))
     );
     assert!(
-        ((((s2.as_pointer() as Ptr<u8>).offset(2_usize as isize).read()) as i32)
-            == (('b' as u8) as i32))
+        ((((s2.as_pointer() as Ptr<u8>).offset(2_usize).read()) as i32) == (('b' as u8) as i32))
     );
     assert!(
-        ((((s1.as_pointer() as Ptr<u8>).offset(0_usize as isize).read()) as i32)
-            == (('a' as u8) as i32))
+        ((((s1.as_pointer() as Ptr<u8>).offset(0_usize).read()) as i32) == (('a' as u8) as i32))
     );
     assert!(
-        ((((s1.as_pointer() as Ptr<u8>).offset(1_usize as isize).read()) as i32)
-            == (('a' as u8) as i32))
+        ((((s1.as_pointer() as Ptr<u8>).offset(1_usize).read()) as i32) == (('a' as u8) as i32))
     );
     assert!(
-        ((((s1.as_pointer() as Ptr<u8>).offset(2_usize as isize).read()) as i32)
-            == (('a' as u8) as i32))
+        ((((s1.as_pointer() as Ptr<u8>).offset(2_usize).read()) as i32) == (('a' as u8) as i32))
     );
     let b1: Value<Bar> = Rc::new(RefCell::new(Bar {
         w: Rc::new(RefCell::new(1)),
@@ -484,26 +478,26 @@ fn main_0() -> i32 {
     'loop_: while ((*i.borrow()) < (*N.borrow())) {
         assert!(
             (((v4.as_pointer() as Ptr<i32>)
-                .offset(((*i.borrow()) as usize) as isize)
+                .offset(((*i.borrow()) as usize))
                 .read())
                 == ((*i.borrow()) + 1))
         );
         (v4.as_pointer() as Ptr<i32>)
-            .offset(((*i.borrow()) as usize) as isize)
+            .offset(((*i.borrow()) as usize))
             .with_mut(|__v| __v.prefix_inc());
         (*i.borrow_mut()).prefix_inc();
     }
     let i: Value<i32> = Rc::new(RefCell::new(0));
     'loop_: while ((*i.borrow()) < (*N.borrow())) {
         assert!(
             (((v4.as_pointer() as Ptr<i32>)
-                .offset(((*i.borrow()) as usize) as isize)
+                .offset(((*i.borrow()) as usize))
                 .read())
                 == ((*i.borrow()) + 2))
         );
         assert!(
             (((v2.as_pointer() as Ptr<i32>)
-                .offset(((*i.borrow()) as usize) as isize)
+                .offset(((*i.borrow()) as usize))
                 .read())
                 == ((*i.borrow()) + 1))
         );