如果在lambda中捕获了独特的指针的元组，则潜在的内存泄漏

Question

clang-tidy和扫描构建警告此代码中的潜在内存泄漏：

#include <tuple>
#include <memory>

int main()
{
    auto lambda = [tuple = std::make_tuple(std::make_unique<int>(42))] {};
}

$ clang-tidy main.cpp -checks="clang*"
1 warning generated.
/foo/main.cpp:7:1: warning: Potential leak of memory pointed to by field '_M_head_impl' [clang-analyzer-cplusplus.NewDeleteLeaks]
}
^
/foo/main.cpp:6:44: note: Calling 'make_unique<int, int>'
    auto lambda = [tuple = std::make_tuple(std::make_unique<int>(42))] {};
                                           ^~~~~~~~~~~~~~~~~~~~~~~~~
/usr/bin/../lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/bits/unique_ptr.h:962:30: note: Memory is allocated
    { return unique_ptr<_Tp>(new _Tp(std::forward<_Args>(__args)...)); }
                             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/foo/main.cpp:6:44: note: Returned allocated memory
    auto lambda = [tuple = std::make_tuple(std::make_unique<int>(42))] {};
                                           ^~~~~~~~~~~~~~~~~~~~~~~~~
/foo/main.cpp:7:1: note: Potential leak of memory pointed to by field '_M_head_impl'
}
^

我看不到任何东西，还是是误报？

---

环境：Clang 13.0.0，GCC 11.3.1。

编译命令：

[
{
  "directory": "/foo",
  "command": "/usr/bin/g++ -std=c++17 /foo/main.cpp",
  "file": "/foo/main.cpp"
}
]

注意：问题可与-STD = C ++ 17和-STD = C ++ 20，但不使用-STD = C ++ 14。

Answer 1

lambda在范围耗尽后被摧毁，并被捕获 - 随着元组的捕获，它也被捕获，它也会被破坏，并与之一起弹性，因此智能指针将其存储在那里。

尝试查看：

#include <iostream>
#include <memory>
#include <tuple>

struct S
{
    S() { std::cout << "constructed" << std::endl; }
    ~S() { std::cout << "destructed" << std::endl; }
};

int main()
{
    auto lambda = [tuple = std::make_tuple(std::make_unique<S>())] {};
    return 0;
}

请参阅 godbolt 。

显然是一个假阳性...

Answer 2

clang-tidy中的一个未解决的错误：
https：//github.com/llvm/llvm/llvm/llvm/llvm-project/issues/552219

它与此注释。