<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/63199>63199</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            clang CUDA. error: no matching constructor for initialization of std::shared_ptr
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          burlen
      </td>
    </tr>
</table>

<pre>
    It seems that clang cuda wrappers overload `free` from the C stdlib in a way that causes some valid C++ code to fail when compiling for cuda. The issue specifically is with overload resolution in the `std::shared_ptr` constructor when using `free` as the deleter.

Here is small reproducer:
```C++
#include <cstdlib>

// note: the noinline issue was fixed in clang may '23
#undef __noinline__
#include <memory>
#define __noinline__ __attribute__((noinline))

int main(int, char**)
{
    unsigned int *tmp = (unsigned int*)malloc(16*sizeof(unsigned int));

    // fails with -x cuda
    auto ptr = std::shared_ptr<unsigned int>(tmp, free);

    return 0;
}
```

To reproduce compile this with:
```
clang++ -std=c++17 -x cuda --cuda-gpu-arch=sm_75 test.cpp
```

The errors are:
```
test.cpp:14:16: error: no matching constructor for initialization of 'std::shared_ptr<unsigned int>'
    auto ptr = std::shared_ptr<unsigned int>(tmp, free);
 ^ ~~~~~~~~~
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/shared_ptr.h:535:7: note: candidate constructor not viable: no known conversion from 'unsigned int *' to 'const weak_ptr<unsigned int>' for 1st argument
 shared_ptr(const weak_ptr<_Tp>& __r, std::nothrow_t) noexcept
 ^
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/shared_ptr.h:231:2: note: candidate template ignored: couldn't infer template argument '_Deleter'
        shared_ptr(_Yp* __p, _Deleter __d)
 ^
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/shared_ptr.h:248:2: note: candidate template ignored: couldn't infer template argument '_Deleter'
        shared_ptr(nullptr_t __p, _Deleter __d)
 ^
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/shared_ptr.h:311:2: note: candidate template ignored: could not match 'shared_ptr<_Yp>' against 'unsigned int *'
        shared_ptr(const shared_ptr<_Yp>& __r, element_type* __p) noexcept
 ^
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/shared_ptr.h:463:2: note: candidate template ignored: could not match '_Sp_alloc_shared_tag<_Alloc>' against 'unsigned int *'
 shared_ptr(_Sp_alloc_shared_tag<_Alloc> __tag, _Args&&... __args)
 ^
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/shared_ptr.h:204:7: note: candidate constructor not viable: requires 1 argument, but 2 were provided
      shared_ptr(const shared_ptr&) noexcept = default; ///< Copy constructor
 ^
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/shared_ptr.h:214:2: note: candidate constructor template not viable: requires single argument '__p', but 2 arguments were provided
        shared_ptr(_Yp* __p) : __shared_ptr<_Tp>(__p) { }
 ^
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/shared_ptr.h:351:2: note: candidate constructor template not viable: requires single argument '__r', but 2 arguments were provided
        shared_ptr(const shared_ptr<_Yp>& __r) noexcept
 ^
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/shared_ptr.h:359:7: note: candidate constructor not viable: requires single argument '__r', but 2 arguments were provided
      shared_ptr(shared_ptr&& __r) noexcept
 ^
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/shared_ptr.h:368:2: note: candidate constructor template not viable: requires single argument '__r', but 2 arguments were provided
        shared_ptr(shared_ptr<_Yp>&& __r) noexcept
 ^
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/shared_ptr.h:380:11: note: candidate constructor template not viable: requires single argument '__r', but 2 arguments were provided
        explicit shared_ptr(const weak_ptr<_Yp>& __r)
 ^
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/shared_ptr.h:387:2: note: candidate constructor template not viable: requires single argument '__r', but 2 arguments were provided
        shared_ptr(auto_ptr<_Yp>&& __r);
 ^
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/shared_ptr.h:395:2: note: candidate constructor template not viable: requires single argument '__r', but 2 arguments were provided
        shared_ptr(unique_ptr<_Yp, _Del>&& __r)
 ^
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/shared_ptr.h:412:17: note: candidate constructor not viable: requires 1 argument, but 2 were provided
      constexpr shared_ptr(nullptr_t) noexcept : shared_ptr() { }
 ^
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/shared_ptr.h:268:2: note: candidate constructor template not viable: requires 3 arguments, but 2 were provided
        shared_ptr(_Yp* __p, _Deleter __d, _Alloc __a)
 ^
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/shared_ptr.h:287:2: note: candidate constructor template not viable: requires 3 arguments, but 2 were provided
        shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a)
 ^
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/shared_ptr.h:202:17: note: candidate constructor not viable: requires 0 arguments, but 2 were provided
      constexpr shared_ptr() noexcept : __shared_ptr<_Tp>() { }
                ^
```
After a bit of digging I found that clang cuda wrappers overload free for use on the device. For instance:

``` C++
#include <cstdlib>

int main(int, char**)
{
    // this line give some additional info. it seems the CUDA
    // wrappers overload free and type of free cannot be deduced.
    using free_t = decltype(free);

    return 0;
}   
```

errors out with:
```
test.cpp:18:29: error: reference to overloaded function could not be resolved; did you mean to call it?
    using free_t = decltype(free);
 ^~~~
/home/bloring/work/llvm/llvm-17_5_25-install/lib/clang/17/include/__clang_cuda_runtime_wrapper.h:405:17: note: possible target for call
__device__ void free(void *) __attribute((nothrow));
                ^
/usr/include/stdlib.h:568:13: note: possible target for call
extern void free (void *__ptr) __THROW;
```
Showing the device overload. Adding an explicit cast on free can be used to help the compiler find the right overload, `auto ptr = std::shared_ptr<unsigned int>(tmp, (void (*)(void *) noexcept(true))free);`
</pre>
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