Write mutable fields through const objects (#520)

Author: lucic71

cpp2rust/converter/converter.cpp

@@ -3019,28 +3019,28 @@ bool Converter::ConvertIncAndDec(clang::UnaryOperator *expr) {
   auto *sub_expr = expr->getSubExpr();
   switch (opcode) {
   case clang::UO_PostInc: {
-    PushExprKind push(*this, ExprKind::RValue);
+    PushExprKind push(*this, ExprKind::LValue);
     Convert(sub_expr);
     StrCat(".postfix_inc()");
     SetFresh();
     return true;
   }
   case clang::UO_PostDec: {
-    PushExprKind push(*this, ExprKind::RValue);
+    PushExprKind push(*this, ExprKind::LValue);
     Convert(sub_expr);
     StrCat(".postfix_dec()");
     SetFresh();
     return true;
   }
   case clang::UO_PreInc: {
-    PushExprKind push(*this, ExprKind::RValue);
+    PushExprKind push(*this, ExprKind::LValue);
     Convert(sub_expr);
     StrCat(".prefix_inc()");
     SetFresh();
     return true;
   }
   case clang::UO_PreDec: {
-    PushExprKind push(*this, ExprKind::RValue);
+    PushExprKind push(*this, ExprKind::LValue);
     Convert(sub_expr);
     StrCat(".prefix_dec()");
     SetFresh();
@@ -3379,6 +3379,21 @@ bool Converter::VisitMemberExpr(clang::MemberExpr *expr) {
     str = std::move(buf).str();
   }
 
+  if (auto *field = clang::dyn_cast<clang::FieldDecl>(member);
+      field && field->isMutable()) {
+    auto *base = expr->getBase();
+    auto object_type = expr->isArrow() ? base->getType()->getPointeeType()
+                                       : base->getType().getNonReferenceType();
+    if (!isRValue() && object_type.isConstQualified()) {
+      if (isAddrOf()) {
+        StrCat(std::format("(&raw const {}).cast_mut()", str));
+        computed_expr_type_ = ComputedExprType::FreshPointer;
+        return false;
+      }
+      str = std::format("(*(&raw const {}).cast_mut())", str);
+    }
+  }
+
   if (isAddrOf()) {
     bool is_reference_type = member->getType()->isReferenceType();
     if (auto *method = clang::dyn_cast<clang::CXXMethodDecl>(member)) {
@@ -3427,22 +3442,12 @@ void Converter::SetUFCSReceiver(clang::Expr *base, bool is_arrow,
   }
   Buffer buf(*this);
   PushExprKind push(*this, ExprKind::LValue);
-  auto object_type = is_arrow ? base->getType()->getPointeeType()
-                              : base->getType().getNonReferenceType();
-  bool cast_mut =
-      MethodNeedsMutableReceiver(method) && object_type.isConstQualified();
   StrCat(MethodNeedsMutableReceiver(method) ? "&mut" : "&");
-  if (cast_mut) {
-    StrCat("*(&raw const");
-  }
   if (is_arrow) {
     ConvertArrow(base);
   } else {
     Convert(base);
   }
-  if (cast_mut) {
-    StrCat(").cast_mut()");
-  }
   ufcs_receiver_ = std::move(buf).str();
 }
 

cpp2rust/converter/converter_lib.cpp

@@ -609,12 +609,7 @@ bool IsRValueConvertingConstructor(const clang::CXXConstructorDecl *ctor) {
 }
 
 bool MethodNeedsMutableReceiver(const clang::CXXMethodDecl *method) {
-  if (!method->isConst()) {
-    return true;
-  }
-  return std::any_of(method->getParent()->field_begin(),
-                     method->getParent()->field_end(),
-                     [](const clang::FieldDecl *f) { return f->isMutable(); });
+  return !method->isConst();
 }
 
 bool IsPassThroughConstructor(const clang::CXXConstructorDecl *ctor) {

tests/unit/class.cpp

@@ -51,6 +51,20 @@ struct Counter {
   }
 };
 
+struct Tally {
+  mutable int calls;
+
+  int SameNameBetweenConstAndNonConst() {
+    calls += 1;
+    return 1;
+  }
+
+  int SameNameBetweenConstAndNonConst() const {
+    calls += 10;
+    return 2;
+  }
+};
+
 int RandomRoute(Route &route) {
   if (route.path.first % 2) {
     return route.path.SetFirst(route.path.SetSecond(10));
@@ -74,5 +88,13 @@ int main() {
   assert(c2 == c1);
   assert(c1.calls == 3);
   assert(c2.calls == 2);
+  Tally t{0};
+  const Tally ct{0};
+  const Tally &rt = t;
+  assert(t.SameNameBetweenConstAndNonConst() == 1);
+  assert(ct.SameNameBetweenConstAndNonConst() == 2);
+  assert(rt.SameNameBetweenConstAndNonConst() == 2);
+  assert(t.calls == 11);
+  assert(ct.calls == 10);
   return 0;
 }

tests/unit/copy_ctor.cpp

@@ -47,6 +47,18 @@ struct OutOfLine {
 
 OutOfLine::OutOfLine(const OutOfLine &o) : v(o.v + 100) { ++copies; }
 
+struct Tracked {
+  mutable int copied_from = 0;
+  Tracked() = default;
+  Tracked(const Tracked &o) { ++o.copied_from; }
+  Tracked &operator=(const Tracked &o) {
+    ++o.copied_from;
+    return *this;
+  }
+};
+
+static void touch(const Tracked *t) { ++t->copied_from; }
+
 static int by_value(Counted c) { return c.v; }
 
 static Counted make(int v) {
@@ -108,5 +120,14 @@ int main() {
   NonConst n2(cn);
   assert(n1.mark == 1);
   assert(n2.mark == 10);
+
+  Tracked t1;
+  Tracked t2(t1);
+  t2 = t1;
+  assert(t1.copied_from == 2);
+  const Tracked ct;
+  Tracked t3(ct);
+  touch(&ct);
+  assert(ct.copied_from == 2);
   return 0;
 }

tests/unit/out/refcount/class.rs

@@ -50,6 +50,12 @@ impl std::cmp::PartialEq for Counter {
     }
 }
 impl std::cmp::Eq for Counter {}
+#[derive(Clone, Record, ByteRepr, VaArg, FnPtrArg, Default)]
+#[byte_size(4)]
+pub struct Tally {
+    #[offset(0)]
+    pub calls: i32,
+}
 pub fn RandomRoute_0(route: Ptr<Route>) -> i32 {
     if ((route.with(|__s| __s.path.first) % 2) != 0) {
         return ({
@@ -105,6 +111,14 @@ fn main_0() -> i32 {
     assert!(({ CounterImpl::operator_eq(&c2.as_pointer(), c1.as_pointer(),) }));
     assert!(({ (*c1.borrow()).calls } == 3));
     assert!(({ (*c2.borrow()).calls } == 2));
+    let t: Value<Tally> = Rc::new(RefCell::new(Tally { calls: 0 }));
+    let ct: Value<Tally> = Rc::new(RefCell::new(Tally { calls: 0 }));
+    let rt: Ptr<Tally> = t.as_pointer();
+    assert!((({ TallyImpl::SameNameBetweenConstAndNonConst_1(&t.as_pointer(),) }) == 1));
+    assert!((({ TallyImpl::SameNameBetweenConstAndNonConst_2(&ct.as_pointer(),) }) == 2));
+    assert!((({ TallyImpl::SameNameBetweenConstAndNonConst_2(&rt,) }) == 2));
+    assert!(({ (*t.borrow()).calls } == 11));
+    assert!(({ (*ct.borrow()).calls } == 10));
     return 0;
 }
 pub trait CounterImpl {
@@ -168,4 +182,22 @@ impl RouteImpl for Ptr<Route> {
         return old_cost;
     }
 }
+pub trait TallyImpl {
+    fn SameNameBetweenConstAndNonConst_1(&self) -> i32;
+    fn SameNameBetweenConstAndNonConst_2(&self) -> i32;
+}
+impl TallyImpl for Ptr<Tally> {
+    fn SameNameBetweenConstAndNonConst_1(&self) -> i32 {
+        {
+            field!((*self), calls).with_mut(|__v| *__v = *__v + 1)
+        };
+        return 1;
+    }
+    fn SameNameBetweenConstAndNonConst_2(&self) -> i32 {
+        {
+            field!((*self), calls).with_mut(|__v| *__v = *__v + 10)
+        };
+        return 2;
+    }
+}
 pub fn __cpp2rust_init_globals() {}

tests/unit/out/refcount/copy_ctor.rs

@@ -175,10 +175,39 @@ impl Clone for OutOfLine {
     }
 }
 impl OutOfLine {}
-pub fn by_value_1(mut c: Counted) -> i32 {
+#[derive(Record, ByteRepr, VaArg, FnPtrArg)]
+#[byte_size(4)]
+pub struct Tracked {
+    #[offset(0)]
+    pub copied_from: i32,
+}
+impl Tracked {
+    pub fn copy_from(o: Ptr<Tracked>) -> Self {
+        let __this: Tracked = Self { copied_from: 0 };
+        field!(o, copied_from).with_mut(|__v| __v.prefix_inc());
+        __this
+    }
+}
+impl Clone for Tracked {
+    fn clone(&self) -> Self {
+        let __src: Value<Tracked> = Rc::new(RefCell::new(Tracked {
+            copied_from: self.copied_from.clone(),
+        }));
+        Tracked::copy_from(__src.as_pointer())
+    }
+}
+impl Default for Tracked {
+    fn default() -> Self {
+        { Tracked { copied_from: 0 } }
+    }
+}
+pub fn touch_1(mut t: Ptr<Tracked>) {
+    field!(t, copied_from).with_mut(|__v| __v.prefix_inc());
+}
+pub fn by_value_2(mut c: Counted) -> i32 {
     return c.v;
 }
-pub fn make_2(mut v: i32) -> Counted {
+pub fn make_3(mut v: i32) -> Counted {
     let c: Value<Counted> = Rc::new(RefCell::new(Counted::new({ v })));
     return Counted::copy_from({ c.as_pointer() });
 }
@@ -193,9 +222,9 @@ fn main_0() -> i32 {
     let mut d: Counted = Counted::copy_from({ a.as_pointer() });
     assert!((copies_0.with(|rc| *rc.borrow()) == 3));
     assert!(((b.v == 1) && (c.v == 1)) && (d.v == 1));
-    assert!((({ by_value_1(Counted::copy_from({ a.as_pointer() },),) }) == 1));
+    assert!((({ by_value_2(Counted::copy_from({ a.as_pointer() },),) }) == 1));
     assert!((copies_0.with(|rc| *rc.borrow()) == 4));
-    let mut e: Counted = ({ make_2(5) });
+    let mut e: Counted = ({ make_3(5) });
     assert!((e.v == 5));
     assert!((copies_0.with(|rc| *rc.borrow()) == 5));
     let mut f: Counted = Counted::new({ 6 });
@@ -255,8 +284,25 @@ fn main_0() -> i32 {
     let mut n2: NonConst = NonConst::new_2({ cn.as_pointer() });
     assert!((n1.mark == 1));
     assert!((n2.mark == 10));
+    let t1: Value<Tracked> = Rc::new(RefCell::new(<Tracked>::default()));
+    let t2: Value<Tracked> = Rc::new(RefCell::new(Tracked::copy_from({ t1.as_pointer() })));
+    ({ TrackedImpl::copy_assign(&t2.as_pointer(), t1.as_pointer()) });
+    assert!(({ (*t1.borrow()).copied_from } == 2));
+    let ct: Value<Tracked> = Rc::new(RefCell::new(<Tracked>::default()));
+    let mut t3: Tracked = Tracked::copy_from({ ct.as_pointer() });
+    ({ touch_1((ct.as_pointer())) });
+    assert!(({ (*ct.borrow()).copied_from } == 2));
     return 0;
 }
+pub trait TrackedImpl {
+    fn copy_assign(&self, o: Ptr<Tracked>) -> Ptr<Tracked>;
+}
+impl TrackedImpl for Ptr<Tracked> {
+    fn copy_assign(&self, o: Ptr<Tracked>) -> Ptr<Tracked> {
+        field!(o, copied_from).with_mut(|__v| __v.prefix_inc());
+        return (*self).clone();
+    }
+}
 pub fn __cpp2rust_init_globals() {
     let _ = copies_0.with(|_| ());
 }

tests/unit/out/unsafe/class.rs

@@ -61,23 +61,36 @@ pub struct Counter {
     pub calls: i32,
 }
 impl Counter {
-    pub unsafe fn Get(&mut self) -> i32 {
-        self.calls.prefix_inc();
+    pub unsafe fn Get(&self) -> i32 {
+        (*(&raw const self.calls).cast_mut()).prefix_inc();
         return self.v;
     }
-    pub unsafe fn operator_eq(&mut self, o: *const Counter) -> bool {
-        self.calls.prefix_inc();
+    pub unsafe fn operator_eq(&self, o: *const Counter) -> bool {
+        (*(&raw const self.calls).cast_mut()).prefix_inc();
         return ((self.v) == ((*o).v));
     }
 }
 impl std::cmp::PartialEq for Counter {
     fn eq(&self, other: &Self) -> bool {
-        unsafe {
-            Counter::operator_eq(&mut *(&raw const *self).cast_mut(), other as *const Counter)
-        }
+        unsafe { Counter::operator_eq(self, other as *const Counter) }
     }
 }
 impl std::cmp::Eq for Counter {}
+#[repr(C)]
+#[derive(Copy, Clone, VaArg, FnPtrArg, Default)]
+pub struct Tally {
+    pub calls: i32,
+}
+impl Tally {
+    pub unsafe fn SameNameBetweenConstAndNonConst_1(&mut self) -> i32 {
+        self.calls += 1;
+        return 1;
+    }
+    pub unsafe fn SameNameBetweenConstAndNonConst_2(&self) -> i32 {
+        (*(&raw const self.calls).cast_mut()) += 10;
+        return 2;
+    }
+}
 pub unsafe fn RandomRoute_0(route: *mut Route) -> i32 {
     if ((((*route).path.first) % (2)) != 0) {
         return (unsafe {
@@ -128,13 +141,21 @@ unsafe fn main_0() -> i32 {
     let mut c1: Counter = Counter { v: 3, calls: 0 };
     let c2: Counter = Counter { v: 3, calls: 0 };
     let mut pc: *const Counter = (&mut c1 as *mut Counter).cast_const();
-    assert!(((unsafe { Counter::Get(&mut *(&raw const c1).cast_mut(),) }) == (3)));
-    assert!(((unsafe { Counter::Get(&mut *(&raw const c2).cast_mut(),) }) == (3)));
-    assert!(((unsafe { Counter::Get(&mut *(&raw const (*pc)).cast_mut(),) }) == (3)));
-    assert!((unsafe { Counter::operator_eq(&mut *(&raw const c1).cast_mut(), &c2,) }));
-    assert!((unsafe { Counter::operator_eq(&mut *(&raw const c2).cast_mut(), &c1,) }));
+    assert!(((unsafe { Counter::Get(&c1,) }) == (3)));
+    assert!(((unsafe { Counter::Get(&c2,) }) == (3)));
+    assert!(((unsafe { Counter::Get(&(*pc),) }) == (3)));
+    assert!((unsafe { Counter::operator_eq(&c1, &c2,) }));
+    assert!((unsafe { Counter::operator_eq(&c2, &c1,) }));
     assert!(((c1.calls) == (3)));
     assert!(((c2.calls) == (2)));
+    let mut t: Tally = Tally { calls: 0 };
+    let ct: Tally = Tally { calls: 0 };
+    let rt: *const Tally = &t;
+    assert!(((unsafe { Tally::SameNameBetweenConstAndNonConst_1(&mut t,) }) == (1)));
+    assert!(((unsafe { Tally::SameNameBetweenConstAndNonConst_2(&ct,) }) == (2)));
+    assert!(((unsafe { Tally::SameNameBetweenConstAndNonConst_2(&(*rt),) }) == (2)));
+    assert!(((t.calls) == (11)));
+    assert!(((ct.calls) == (10)));
     return 0;
 }
 pub unsafe fn __cpp2rust_init_globals() {}