https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109538
Bug ID: 109538
Summary: Spurious -Werror=dangling-reference false positive
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: [email protected]
Target Milestone: ---
gcc 13.0.1 would like to register a complaint:
t.C:17:14: error: possibly dangling reference to a temporary
[-Werror=dangling-reference]
17 | const int &v=optional_arg_or(def, 0);
| ^
t.C:17:31: note: the temporary was destroyed at the end of the full expression
‘optional_arg_or(def, 0)’
17 | const int &v=optional_arg_or(def, 0);
| ~~~~~~~~~~~~~~~^~~~~~~~
for:
#include <optional>
#include <utility>
const int &optional_arg_or(std::optional<int> &def,
int &&def_val)
{
def = def_val;
return *def;
}
int gimme()
{
std::optional<int> def;
const int &v=optional_arg_or(def, 0);
int bologna=v;
return bologna;
}
Changing optional_arg_or's parameter to "int def_val" silences the complaint.
gcc appears to be voicing an objection that optional_arg_or returns a reference
to a temporary that gets created during the function call and destroyed at the
conclusion of the function call. However that temporary gets placed into a
std::optional, and then a reference to the std::optional gets returned.
