1c99907222
In C++20 constexpr virtual function is allowed. In C++17 although
non-pure virtual function is not allowed to be constexpr, pure virtual
function is allowed to be constexpr and is allowed to be overriden by
non-constexpr virtual function in the derived class.
The following code compiles as C++:
```
class A
{
public:
constexpr virtual int f() = 0;
};
class B : public A
{
public:
int f() override
{
return 42;
}
};
```
However, it fails to compile as CUDA or HIP code. The reason: A::f() is
implicitly host device function whereas B::f() is a host function. Since
they have different targets, clang does not treat B::f() as an override
of A::f(). Instead, it treats B::f() as a name-hiding non-virtual
function for A::f(), and diagnoses it.
This causes any CUDA/HIP program using C++ standard header file
`<format>` from g++-13 to fail to compile since such usage patten show
up there:
```
/usr/lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/format:3564:34: error: non-virtual member function marked 'override' hides virtual member function
3564 | _M_format_arg(size_t __id) override
| ^
/usr/lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/format:3538:30: note: hidden overloaded virtual function 'std::__format::_Scanner<char>::_M_format_arg' declared here
3538 | constexpr virtual void _M_format_arg(size_t __id) = 0;
| ^
```
This is a serious issue and there is no workaround.
This patch allows non-constexpr function to override constexpr virtual
function for CUDA and HIP. This should be OK since non-constexpr
function without explicit host or device attribute can only be called in
host functions.
Fixes: SWDEV-507350
29 lines
410 B
Plaintext
29 lines
410 B
Plaintext
// RUN: %clang_cc1 -triple nvptx64-nvidia-cuda -fsyntax-only \
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// RUN: -fcuda-is-device %s
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// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fsyntax-only %s
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// expected-no-diagnostics
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#include "Inputs/cuda.h"
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class A
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{
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public:
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constexpr virtual int f() = 0;
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};
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class B : public A
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{
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public:
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int f() override
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{
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return 42;
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}
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};
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int test()
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{
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B b;
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return b.f();
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}
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