[llvm-bugs] [Bug 51695] New: Clang not emitting destructor call when assignment constructed with list

via llvm-bugs llvm-bugs at lists.llvm.org
Tue Aug 31 16:25:01 PDT 2021


https://bugs.llvm.org/show_bug.cgi?id=51695

            Bug ID: 51695
           Summary: Clang not emitting destructor call when assignment
                    constructed with list
           Product: clang
           Version: trunk
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++17
          Assignee: unassignedclangbugs at nondot.org
          Reporter: lxfind at gmail.com
                CC: blitzrakete at gmail.com, erik.pilkington at gmail.com,
                    llvm-bugs at lists.llvm.org, richard-llvm at metafoo.co.uk

In the following code: https://godbolt.org/z/TK7ersK1M

#include <string>
#include <utility>

void doSomething();

class FooClass {
 public:
  FooClass() noexcept : ptr_() {}

  FooClass(FooClass&& other) noexcept
      : ptr_(std::exchange(other.ptr_, {})) {}

  ~FooClass() {
    doSomething();
  }

  FooClass& operator=(FooClass other) noexcept {
    std::swap(ptr_, other.ptr_);
    return *this;
  }

 private:
  void *ptr_;
};

template <typename T>
class WrapperClass {
 public:
  void run() noexcept {
    wrapper_ = {};
  }

 private:
  FooClass wrapper_;
};

void foo(WrapperClass<std::string> &A) {
    A.run();
}


When compiled with either GCC (any std version) or Clang with C++14, the line
"wrapper_ = {};" in WrapperClass::run() will always generate a destructor call
in the end, which is expected.
However when compiled with Clang C++17, the destructor call is not generated,
which seems wrong to me.

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