[Bug c++/79679] New: [C++17] Missing destruction of temporary within constructor's mem-initializer-list

[sbergman at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79679

            Bug ID: 79679
           Summary: [C++17] Missing destruction of temporary within
                    constructor's mem-initializer-list
           Product: gcc
           Version: 7.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sbergman at redhat dot com
  Target Milestone: ---

At least with a recent GCC trunk build ("gcc (GCC) 7.0.1 20170221
(experimental)"), the below program does not print "dtor" when built with
-std=c++17 (but does when built with -std=c++14, or with an older GCC,
gcc-c++-6.3.1-1.fc25.x86_64).  Appears that in the U ctor, a temporary
shared_ptr<S> is copy-created but not destroyed.


#include <iostream>
#include <memory>
struct S { ~S() { std::cout << "dtor\n"; } };
struct T {
    std::shared_ptr<S> s_;
    T(std::shared_ptr<S> s): s_(s) {}
};
struct U {
    T t_;
    U(std::shared_ptr<S> const & s): t_(s) {}
};
int main() {
    auto s = std::make_shared<S>();
    U u(s);
}