https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117155
Bug ID: 117155
Summary: Bogus -Wdangling-reference warning after
r13-3511-gd2249cd9adf
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: dimi...@unified-streaming.com
Target Milestone: ---
After r15-3941-g2531f014fb2364 ("c++: Implement -Wdangling-reference
[PR106393]") for 106393, we are now seeing bogus instances of this new warning.
Since the commit message marks this as an "experimental warning", I would
suggest to not put this under -Wall, at least until it is no longer
experimental, and false positives have been ferreted out.
Reduced test case:
$ cat dangling-ref.cpp
#include <algorithm>
#include <stdexcept>
#include <string>
#include <vector>
template <typename Predicate>
std::string const &
find (std::vector<std::string> const &vec, Predicate predicate)
{
if (auto iter = std::find_if (vec.begin (), vec.end (), predicate);
iter != vec.end ())
{
return *iter;
}
throw std::runtime_error ("stream not found");
}
struct match_t
{
match_t (std::string name) : name_ (std::move (name)) {}
bool
operator() (std::string const &s) const
{
return s == name_;
}
private:
std::string name_;
};
void f (std::string const &);
void
g (std::string const &name, std::vector<std::string> const &vec)
{
match_t match (name);
auto const &s = find (vec, match);
f (s);
}
$ ~/ins/gcc-13-3510-gf896c13489d/bin/g++ -Wall -c dangling-ref.cpp
$ ~/ins/gcc-13-3511-gd2249cd9adf/bin/g++ -Wall -c dangling-ref.cpp
dangling-ref.cpp: In function 'void g(const std::string&, const
std::vector<std::__cxx11::basic_string<char> >&)':
dangling-ref.cpp:39:15: warning: possibly dangling reference to a temporary
[-Wdangling-reference]
39 | auto const &s = find (vec, match);
| ^
dangling-ref.cpp:39:24: note: the temporary was destroyed at the end of the
full expression 'find<match_t>((* & vec), match_t(match))'
39 | auto const &s = find (vec, match);
| ~~~~~^~~~~~~~~~~~
Clearly, there is no dangling reference here, and not even a temporary. And
even if there was a temporary, its lifetime should have been extended.
