[llvm-bugs] [Bug 25911] New: -Wpessimizing-move doesn't trigger inside template instantiations

via llvm-bugs llvm-bugs at lists.llvm.org
Mon Dec 21 12:05:33 PST 2015


            Bug ID: 25911
           Summary: -Wpessimizing-move doesn't trigger inside template
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++11
          Assignee: unassignedclangbugs at nondot.org
          Reporter: dcheng at google.com
                CC: dgregor at apple.com, llvm-bugs at lists.llvm.org
    Classification: Unclassified

https://llvm.org/bugs/show_bug.cgi?id=9679 is a bug that indicates that it's
generally unsafe to emit fix-its inside template instantiations.

However, this leads to omission of a pessimizing-move warning in some
circumstances where it could apply. One example:

dcheng at nausicaa:~/src/chrome/src$ cat test.cc                                   
#include <utility>

template<typename T>
class my_scoped_ptr {
  explicit my_scoped_ptr(T* ptr) : ptr_(ptr) {}
  ~my_scoped_ptr() { delete ptr_; }

  my_scoped_ptr(my_scoped_ptr&& other) : ptr_(nullptr) { 
    using std::swap;
    swap(ptr_, other.ptr_);

  static my_scoped_ptr New() { return std::move(my_scoped_ptr(nullptr)); }

  T* ptr_;

int main() {
  my_scoped_ptr<int> scoper = my_scoped_ptr<int>::New();
dcheng at nausicaa:~/src/chrome/src$
third_party/llvm-build/Release+Asserts/bin/clang++ -std=c++11 -W
all test.cc
dcheng at nausicaa:~/src/chrome/src$

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