https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80544
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
See Also| |https://gcc.gnu.org/bugzill
| |a/show_bug.cgi?id=49395
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I tried to add a warning like this:
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -6633,6 +6633,10 @@ maybe_warn_about_useless_cast (tree type, tree expr,
tsubst_flags_t complain)
|| same_type_p (TREE_TYPE (expr), type))
warning (OPT_Wuseless_cast, "useless cast to type %qT", type);
}
+ else if (complain & tf_warning && !CLASS_TYPE_P (type)
+ && (TREE_CODE (type) != ARRAY_TYPE)
+ && (CP_TYPE_CONST_P (type) || CP_TYPE_VOLATILE_P (type)))
+ warning (0, "cv-qualifier ignored in cast");
}
/* Convert EXPR (an expression with pointer-to-member type) to TYPE
The warning works for the examples above, but also produces warnings for this
valid C++17 code:
enum class E { };
E e{1};
It also causes a dozen or so FAILs in the testsuite, which in some cases are
due to useless cv-qualifiers that should be ignroed, and in some cases might
need to be suppressed with a -Wno-xxx option (because the test is intentionally
casting to a const type).
This attempts to fix the actual bug, and seems to work OK:
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -6708,6 +6708,10 @@ build_static_cast_1 (tree type, tree expr, bool
c_cast_p,
/* Save casted types in the function's used types hash table. */
used_types_insert (type);
+ /* Result of cast to pointer is prvalue of cv-unqualified type. */
+ if (TREE_CODE (type) == POINTER_TYPE)
+ type = cv_unqualified (type);
+
/* [expr.static.cast]
An lvalue of type "cv1 B", where B is a class type, can be cast
@@ -7070,6 +7074,10 @@ build_reinterpret_cast_1 (tree type, tree expr, bool
c_cast_p,
/* Save casted types in the function's used types hash table. */
used_types_insert (type);
+ /* Result of cast to pointer is prvalue of cv-unqualified type. */
+ if (TREE_CODE (type) == POINTER_TYPE)
+ type = cv_unqualified (type);
+
/* [expr.reinterpret.cast]
An lvalue expression of type T1 can be cast to the type
"reference to T2" if an expression of type "pointer to T1" can be
@@ -7300,6 +7308,10 @@ build_const_cast_1 (tree dst_type, tree expr,
tsubst_flags_t complain,
/* Save casted types in the function's used types hash table. */
used_types_insert (dst_type);
+ /* Result of cast to pointer is prvalue of cv-unqualified type. */
+ if (TREE_CODE (dst_type) == POINTER_TYPE)
+ dst_type = cv_unqualified (dst_type);
+
src_type = TREE_TYPE (expr);
/* Expressions do not really have reference types. */
if (TREE_CODE (src_type) == REFERENCE_TYPE)
