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From: "loximann at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug sanitizer/102095] New: Returned reference to temporary not
 caught by -fsanitize=undefined
Date: Fri, 27 Aug 2021 11:28:18 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102095

            Bug ID: 102095
           Summary: Returned reference to temporary not caught by
                    -fsanitize=3Dundefined
           Product: gcc
           Version: 11.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: sanitizer
          Assignee: unassigned at gcc dot gnu.org
          Reporter: loximann at gmail dot com
                CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
                    jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxi=
n at gcc dot gnu.org
  Target Milestone: ---

The following code results in undefined behaviour (I believe), but it is not
caught by -fsanitize=3Dundefined:

#include <functional>
#include <iostream>
#include <tuple>

template <typename T>
std::function<const T&()> constant(const T& c) {
  return [c]() noexcept -> const T&{ return c; };
}

template <typename T>
std::function<std::tuple<T>()> zip_good(const std::function<T()>& f) {
  return [f]() { return std::tuple<T>{f()}; };
}

template <typename T>
std::function<std::tuple<T>()> zip_bad(const std::function<T()>& f) {
  return [f]() { return std::tuple{f()}; }; // <- UNDEFINED if T is const r=
ef
}

int main() {
    std::cout << std::get<0>(zip_good(constant(1.0))()) << std::endl;
    std::cout << std::get<0>(zip_bad(constant(1.0))()) << std::endl;
}=