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<head>
<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Clang-cl link error exported class with template as base"
href="https://bugs.llvm.org/show_bug.cgi?id=37998">37998</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Clang-cl link error exported class with template as base
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>6.0
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Windows NT
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>-New Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>jvapen@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=20495" name="attach_20495" title="Reproduction">attachment 20495</a> <a href="attachment.cgi?id=20495&action=edit" title="Reproduction">[details]</a></span>
Reproduction
Using MSVC 2017 and Clang-cl 6.0.0
Given link error:
u.clang.obj : error LNK2019: unresolved external symbol "private: int * __cdecl
NS::A<struct N::S>::get<int>(void)" (??$get@H@?$A@US@N@@@NS@@AEAAPEAHXZ)
referenced in function "int __cdecl func(int,char * *)" (?func@@YAHHPEAPEAD@Z)
In attachment, you can find the same files as below.
run.cmd
-------
cl.exe /nologo /c /GR /EHsc /fp:precise /FS /std:c++17 /diagnostics:caret /O2
/I. /MDd /Zc:forScope /bigobj /Zc:wchar_t t.cpp
cl.exe /nologo /c /GR /EHsc /fp:precise /FS /std:c++17 /diagnostics:caret /O2
/I. /MDd /Zc:forScope /bigobj /Zc:wchar_t u.cpp
cl.exe /nologo /c /GR /EHsc /fp:precise /FS /std:c++17 /diagnostics:caret /O2
/I. /MDd /Zc:forScope /bigobj /Zc:wchar_t m.cpp
move t.obj t.msvc.obj
move u.obj u.msvc.obj
move m.obj m.msvc.obj
link m.msvc.obj t.msvc.obj u.msvc.obj
clang-cl.exe -fms-compatibility-version=19.11 /DBOOST_USE_WINDOWS_H -w
-Wno-unused-command-line-argument /nologo /c /GR /EHsc /fp:precise /FS
/std:c++17 /diagnostics:caret /O2 /I. /MDd /Zc:forScope /bigobj /Zc:wchar_t
t.cpp
clang-cl.exe -fms-compatibility-version=19.11 /DBOOST_USE_WINDOWS_H -w
-Wno-unused-command-line-argument /nologo /c /GR /EHsc /fp:precise /FS
/std:c++17 /diagnostics:caret /O2 /I. /MDd /Zc:forScope /bigobj /Zc:wchar_t
u.cpp
clang-cl.exe -fms-compatibility-version=19.11 /DBOOST_USE_WINDOWS_H -w
-Wno-unused-command-line-argument /nologo /c /GR /EHsc /fp:precise /FS
/std:c++17 /diagnostics:caret /O2 /I. /MDd /Zc:forScope /bigobj /Zc:wchar_t
m.cpp
move t.obj t.clang.obj
move u.obj u.clang.obj
move m.obj m.clang.obj
link m.clang.obj t.clang.obj u.clang.obj
t.h
---
#include <type_traits>
#ifdef EXPORT_DLL
#define EXPORT __declspec(dllexport)
#else
#define EXPORT __declspec(dllimport)
#endif
namespace N {
struct S {};
} // namespace N
namespace NS {
struct I {
virtual ~I() = default;
virtual int *f() = 0;
};
template <typename T> class A : public I {
public:
explicit A() = default;
virtual ~A() = default;
A(const A &) = default;
A(A &&) = default;
A &operator=(const A &) = default;
A &operator=(A &&) = default;
virtual int *f() override { return get<int>(); }
private:
template <typename Q, bool selection = std::is_base_of<Q, T>::value>
struct Impl {
Q *get();
};
template <typename Q> struct Impl<Q, false> {
Q *get() { return nullptr; }
};
//! Wrapper method
template <typename Q> Q *get();
};
} // namespace NS
namespace N {
class EXPORT B : public NS::A<S> {
public:
explicit B();
virtual ~B();
B(const B &) = default;
B(B &&) = default;
B &operator=(const B &) = default;
B &operator=(B &&) = default;
};
} // namespace N
t.cpp
-----
#define EXPORT_DLL
#include "t.h"
namespace NS {
template <typename T>
template <typename Q, bool selection>
Q *A<T>::Impl<Q, selection>::get() {
static int i = 42;
return &i;
}
template <typename T> template <typename Q> Q *A<T>::get() {
return Impl<Q>().get();
}
} // namespace NS
using namespace N;
using namespace NS;
B::B() = default;
B::~B() = default;
template class EXPORT NS::A<S>;
u.cpp
-----
#define EXPORT_DLL
#include "t.h"
using namespace N;
int func(int, char **) {
auto b = B{};
return *b.f();
}
m.cpp
-----
#include "t.h"
using namespace N;
int main(int, char **) {
auto b = B{};
return *b.f();
}</pre>
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