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[clang] trigger -Wcast-qual on functional casts
-Wcast-qual does not trigger on the following code in Clang, but does in GCC. const auto i = 42; using T = int*; auto p = T(&i); The expected behavior is that a functional cast should trigger the warning the same as the equivalent C cast because the meaning is the same, and nothing about the functional cast makes it easier to recognize that a const_cast is occurring. Fixes llvm#62083 Differential Revision: https://reviews.llvm.org/D148276
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‎clang/docs/ReleaseNotes.rst

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@@ -231,6 +231,8 @@ Improvements to Clang's diagnostics
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- ``-Wformat`` now recognizes ``%lb`` for the ``printf``/``scanf`` family of
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functions.
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(`#62247: <https://github.com/llvm/llvm-project/issues/62247>`_).
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- ``-Wcast-qual`` now triggers on function-style casts.
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(`#62083 <https://github.com/llvm/llvm-project/issues/62083>`_)
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Bug Fixes in This Version
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-------------------------

‎clang/lib/Sema/SemaCast.cpp

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@@ -3332,6 +3332,9 @@ ExprResult Sema::BuildCXXFunctionalCastExpr(TypeSourceInfo *CastTypeInfo,
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if (auto *ConstructExpr = dyn_cast<CXXConstructExpr>(SubExpr))
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ConstructExpr->setParenOrBraceRange(SourceRange(LPLoc, RPLoc));
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// -Wcast-qual
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DiagnoseCastQual(Op.Self, Op.SrcExpr, Op.DestType);
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return Op.complete(CXXFunctionalCastExpr::Create(
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Context, Op.ResultType, Op.ValueKind, CastTypeInfo, Op.Kind,
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Op.SrcExpr.get(), &Op.BasePath, CurFPFeatureOverrides(), LPLoc, RPLoc));

‎clang/test/SemaCXX/warn-cast-qual.cpp

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@@ -34,6 +34,17 @@ void foo_0() {
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const int &a6 = (int &)((int &)a); // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}}
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const int &a7 = (int &)((const int &)a); // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}}
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const int &a8 = (const int &)((int &)a); // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}}
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using T = int&;
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using T2 = const int&;
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const int &a11 =T2(a); // no warning
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int a22 = T(a); // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}}
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const int &a33 = T(a); // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}}
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int &a44 = T(T2(a)); // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}}
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int &a55 = T(T(a)); // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}}
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const int &a66 = T(T(a)); // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}}
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int &a77 = T(T2(a)); // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}}
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const int &a88 = T2(T(a)); // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}}
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}
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void foo_1() {
@@ -49,6 +60,17 @@ void foo_1() {
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volatile int &a6 = (int &)((int &)a); // expected-warning {{cast from 'volatile int' to 'int &' drops volatile qualifier}}
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volatile int &a7 = (int &)((volatile int &)a); // expected-warning {{cast from 'volatile int' to 'int &' drops volatile qualifier}}
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volatile int &a8 = (volatile int &)((int &)a); // expected-warning {{cast from 'volatile int' to 'int &' drops volatile qualifier}}
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using T = int&;
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using T2 = volatile int&;
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volatile int &a11 =T2(a); // no warning
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int a22 = T(a); // expected-warning {{cast from 'volatile int' to 'int &' drops volatile qualifier}}
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volatile int &a33 = T(a); // expected-warning {{cast from 'volatile int' to 'int &' drops volatile qualifier}}
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int &a44 = T(T2(a)); // expected-warning {{cast from 'volatile int' to 'int &' drops volatile qualifier}}
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int &a55 = T(T(a)); // expected-warning {{cast from 'volatile int' to 'int &' drops volatile qualifier}}
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volatile int &a66 = T(T(a)); // expected-warning {{cast from 'volatile int' to 'int &' drops volatile qualifier}}
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int &a77 = T(T2(a)); // expected-warning {{cast from 'volatile int' to 'int &' drops volatile qualifier}}
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volatile int &a88 = T2(T(a)); // expected-warning {{cast from 'volatile int' to 'int &' drops volatile qualifier}}
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}
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void foo_2() {
@@ -64,6 +86,17 @@ void foo_2() {
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const volatile int &a6 = (int &)((int &)a); // expected-warning {{cast from 'const volatile int' to 'int &' drops const and volatile qualifiers}}
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const volatile int &a7 = (int &)((const volatile int &)a); // expected-warning {{cast from 'const volatile int' to 'int &' drops const and volatile qualifiers}}
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const volatile int &a8 = (const volatile int &)((int &)a); // expected-warning {{cast from 'const volatile int' to 'int &' drops const and volatile qualifiers}}
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using T = int&;
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using T2 = const volatile int&;
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const volatile int &a11 =T2(a); // no warning
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int a22 = T(a); // expected-warning {{cast from 'const volatile int' to 'int &' drops const and volatile qualifiers}}
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const volatile int &a33 = T(a); // expected-warning {{cast from 'const volatile int' to 'int &' drops const and volatile qualifiers}}
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int &a44 = T(T2(a)); // expected-warning {{cast from 'const volatile int' to 'int &' drops const and volatile qualifiers}}
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int &a55 = T(T(a)); // expected-warning {{cast from 'const volatile int' to 'int &' drops const and volatile qualifiers}}
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const volatile int &a66 = T(T(a)); // expected-warning {{cast from 'const volatile int' to 'int &' drops const and volatile qualifiers}}
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const volatile int &a77 = T(T2(a)); // expected-warning {{cast from 'const volatile int' to 'int &' drops const and volatile qualifiers}}
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const volatile int &a88 = T2(T(a)); // expected-warning {{cast from 'const volatile int' to 'int &' drops const and volatile qualifiers}}
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}
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void bar_0() {
@@ -78,6 +111,16 @@ void bar_0() {
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const int **a4 = (const int **)((int **)a); // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}} expected-warning {{cast from 'int **' to 'const int **' must have all intermediate pointers const qualified to be safe}}
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const int **a5 = (const int **)((const int **)a); // no warning
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using T = int**;
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using T2 = const int**;
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int **a00 = T(T2(a)) ; // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}}
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int **a11 = T(T(a)); // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}}
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const int **a44 = T2(T(a)); // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}} expected-warning {{cast from 'T' (aka 'int **') to 'T2' (aka 'const int **') must have all intermediate pointers const qualified to be safe}}
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const int **a55 = T2(T2(a)); // no warning
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}
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void bar_1() {
@@ -92,6 +135,15 @@ void bar_1() {
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const int *&a4 = (const int *&)((int *&)a); // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}} expected-warning {{cast from 'int *' to 'const int *&' must have all intermediate pointers const qualified to be safe}}
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const int *&a5 = (const int *&)((const int *&)a); // no warning
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using T = int*&;
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using T2 = const int*&;
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int *&a00 = T(T2(a)); // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}}
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int *&a11 = T(T(a)); // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}}
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const int *&a44 = T2(T(a)); // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}} expected-warning {{cast from 'int *' to 'T2' (aka 'const int *&') must have all intermediate pointers const qualified to be safe}}
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const int *&a55 = T2(T2(a)); // no warning
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}
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void baz_0() {
@@ -108,6 +160,14 @@ void baz_0() {
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((C *)&S)->B(); // expected-warning {{cast from 'const C *' to 'C *' drops const qualifier}}
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((C *)&S)->A(); // expected-warning {{cast from 'const C *' to 'C *' drops const qualifier}}
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using T = C&;
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using T2 = C*;
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T(S).B(); // expected-warning {{cast from 'const C' to 'C &' drops const qualifier}}
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T(S).A(); // expected-warning {{cast from 'const C' to 'C &' drops const qualifier}}
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T2(&S)->B(); // expected-warning {{cast from 'const C *' to 'C *' drops const qualifier}}
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T2(&S)->A(); // expected-warning {{cast from 'const C *' to 'C *' drops const qualifier}}
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}
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void baz_1() {
@@ -127,6 +187,14 @@ void baz_1() {
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*(int *)(&S.a) = 0; // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}}
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*(int *)(&S.b) = 0; // no warning
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using T = int&;
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using T2 = int*;
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T(S.a) = 0; // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}}
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T(S.b) = 0; // no warning
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*T2(&S.a) = 0; // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}}
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*T2(&S.b) = 0; // no warning
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}
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{
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const C S;
@@ -136,5 +204,39 @@ void baz_1() {
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*(int *)(&S.a) = 0; // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}}
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*(int *)(&S.b) = 0; // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}}
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using T = int&;
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using T2 = int*;
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T(S.a) = 0; // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}}
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T(S.b) = 0; // expected-warning {{cast from 'const int' to 'int &' drops const qualifier}}
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*T2(&S.a) = 0; // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}}
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*T2(&S.b) = 0; // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}}
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}
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}
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void qux_0() {
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const auto i = 42;
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using T = int*;
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auto p = T(&i); // expected-warning {{cast from 'const int *' to 'int *' drops const qualifier}}
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const auto i2 = 42;
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using T2 = const int*;
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auto p2 = T2(&i2);
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volatile auto i3 = 42;
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using T3= int*;
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auto p3 = T3(&i3); // expected-warning {{cast from 'volatile int *' to 'int *' drops volatile qualifier}}
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volatile auto i4 = 42;
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using T4 = volatile int*;
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auto p4 = T4(&i4);
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const volatile auto i5 = 42;
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using T5= int*;
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auto p5 = T5(&i5); // expected-warning {{cast from 'const volatile int *' to 'int *' drops const and volatile qualifiers}}
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const volatile auto i6 = 42;
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using T6= const volatile int*;
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auto p6 = T6(&i6);
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}

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