[llvm-dev] Clang++: No member name 'make_unique' in namespace 'std'

[users users via llvm-dev]

Dear LLVM Developers:

1.   Recently I built llvm/12.0 on IBM power8 using gcc/8.2.0. When I run
clang++ with an example from
https://en.cppreference.com/w/cpp/memory/unique_ptr/make_unique:

 #include <iostream>

#include <iomanip>#include <memory>
 struct Vec3{
    int x, y, z;

    // following constructor is no longer needed since C++20
    Vec3(int x = 0, int y = 0, int z = 0) noexcept : x(x), y(y), z(z) { }

    friend std::ostream
<http://en.cppreference.com/w/cpp/io/basic_ostream>&
operator<<(std::ostream
<http://en.cppreference.com/w/cpp/io/basic_ostream>& os, const Vec3&
v) {
        return os << "{ x=" << v.x << ", y=" << v.y << ", z=" << v.z << " }";
    }};
 int main(){
    // Use the default constructor.
    std::unique_ptr
<http://en.cppreference.com/w/cpp/memory/unique_ptr><Vec3> v1 =
std::make_unique<Vec3>();
    // Use the constructor that matches these arguments
    std::unique_ptr
<http://en.cppreference.com/w/cpp/memory/unique_ptr><Vec3> v2 =
std::make_unique<Vec3>(0,1,2);
    // Create a unique_ptr to an array of 5 elements
    std::unique_ptr
<http://en.cppreference.com/w/cpp/memory/unique_ptr><Vec3[]> v3 =
std::make_unique<Vec3[]>(5);

    std::cout <http://en.cppreference.com/w/cpp/io/cout> <<
"make_unique<Vec3>():      " << *v1 << '\n'
              << "make_unique<Vec3>(0,1,2): " << *v2 << '\n'
              << "make_unique<Vec3[]>(5):   ";
    for (int i = 0; i < 5; i++) {
        std::cout <http://en.cppreference.com/w/cpp/io/cout> <<
std::setw <http://en.cppreference.com/w/cpp/io/manip/setw>(i ? 30 : 0)
<< v3[i] << '\n';
    }}


It failed with the following errors:
    Error: no member named 'make_unique' in namespace 'std'
       std::unique_ptr<Vec3> v1 = std::make_unique<Vec3>();
    ... ...

Any idea and suggestion about what is going on? or have I missed something?
The command I used to compile the code above:
     $ clang++ a.cpp

2.  Comparing this llvm with my current gcc/8.2.0 on a project (openmp code
running 1 thread), it showed that llvm is almost twice as slow as gcc (both
compile with -O3) on my IBM power8 machine. Is it suppose to be with such
slower performance than gcc?

Thank you very much for any advice!

Best Regards,
Shelton
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