[Bug c++/109671] New: Spurious dangling reference warning in GCC 13

[lopresti at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109671

            Bug ID: 109671
           Summary: Spurious dangling reference warning in GCC 13
           Product: gcc
           Version: 13.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: lopresti at gmail dot com
  Target Milestone: ---

#include <string>

struct Foo;

extern Foo &get_foo_by_name(const std::string &name);

const Foo &bug(bool x)
{
  const Foo &f = get_foo_by_name(x ? "x" : "y");
  return f;
}

---

Compile with "-O2 -Wall" to get the incorrect warning:

<source>: In function 'const Foo& bug(bool)':
<source>:9:14: warning: possibly dangling reference to a temporary
[-Wdangling-reference]
    9 |   const Foo &f = get_foo_by_name(x ? "x" : "y");
      |              ^
<source>:9:33: note: the temporary was destroyed at the end of the full
expression 'get_foo_by_name(std::__cxx11::basic_string<char>(((const char*)(x ?
"x" : "y")), std::allocator<char>()))'
    9 |   const Foo &f = get_foo_by_name(x ? "x" : "y");
      |                  ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~

--

Godbolt: https://godbolt.org/z/cn4W7ohGb

The code is fine. (And no other compiler warns about this, including earlier
GCC versions.)