https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110358
Bug ID: 110358
Summary: requesting nicer suppression for Wdangling-reference
Product: gcc
Version: 13.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: barry.revzin at gmail dot com
Target Milestone: ---
As everyone is already aware, Wdangling-reference gives false positives for
reference-semantic classes. The compiler has special cases for the ones it
knows about, but not for mine. So:
template <typename T>
struct Span {
T* data_;
int len_;
[[nodiscard]] constexpr auto operator[](int n) const noexcept -> T& {
return data_[n]; }
[[nodiscard]] constexpr auto front() const noexcept -> T& { return
data_[0]; }
[[nodiscard]] constexpr auto back() const noexcept -> T& { return
data_[len_ - 1]; }
};
auto get() -> Span<int>;
auto f() -> int {
int const& a = get().front(); // warning
int const& b = get().back(); // warning
int const& c = get()[0]; // warning
return a + b + c;
}
The suppression for this is to #pragma around all my functions, which is a bit
of a tedious suppression, since this is two prefix lines and one postfix line
(but for libraries it's actually 4 prefix lines because we can't ignore
Wdangling-reference until gcc 13, so need to #ifdef that out).
It'd be nice if we could:
* add an attribute to a class to conditionally suppress the warning
* add an attribute to a function to conditionally suppress the warning
* both
Basically in this case to let me do something like:
template <typename T>
struct [[gnu::marek_is_awesome_but_this_warning_has_too_many_false_positives]]
Span {
// ...
};
And I say conditional so that I can do this (because Optional<int&> wants to
suppress the warning, but Optional<int> definitely does not!)
template <typename T>
struct
[[gnu::marek_is_awesome_but_this_warning_has_too_many_false_positives(std::is_reference_v<T>)]]
Optional {
// ...
};
Obviously I am not the best at naming.
