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From: "marco.clemencic at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/107138] [12/13 regression] std::variant<std::string, ...>
 triggers false-positive 'may be used uninitialized' warning
Date: Thu, 17 Nov 2022 11:49:24 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107138

--- Comment #4 from Marco Clemencic <marco.clemencic at gmail dot com> ---
I have a similar problem with this chunk of code:
```
#include <map>
#include <memory>
#include <string>
#include <utility>
#include <variant>

struct Wrapper {
    using Map =3D std::map<std::string, std::string>;
    using Value =3D std::variant<std::string, Map>;
    Wrapper(Value v) : data{std::move(v)} {}
    Value data;
};

auto f() {
    Wrapper::Map r;
    return std::make_unique<Wrapper>(std::move(r)); // <- warning here
    // return std::make_unique<Wrapper>(r); // <- no warning
    // return Wrapper(std::move(r)); // <- no warning
}
```
but the uninitialized variable is coming from std::unique_ptr.

As in the original report it works with gcc 11.3, but it fails with gcc12.2=
 and
trunk (in my case already with -O1), see https://godbolt.org/z/bfo9vsEPc

I attached the .ii produced by my test case.=