[llvm-bugs] [Bug 52044] New: non-type template argument constexpr when passed by reference

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=52044

            Bug ID: 52044
           Summary: non-type template argument constexpr when passed by
                    reference
           Product: clang
           Version: 12.0
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: alexeytech at gmail.com
                CC: blitzrakete at gmail.com, dgregor at apple.com,
                    erik.pilkington at gmail.com, llvm-bugs at lists.llvm.org,
                    richard-llvm at metafoo.co.uk

Hi,

the following code does not work with clang++ 12 and trunk version

***

#include<cstring>
#include<array>

template<size_t N> struct S {
    static constexpr size_t n = N;
};

template<size_t N>
void foo(const S<N> &s) {
    std::array<char, s.n> arr;
}

int main() {
    foo(S<3>{});
}

***

It fails with error

error: non-type template argument is not a constant expression
    std::array<char, s.n> arr;

The gcc and msvc compile this snippet without issues
(https://godbolt.org/z/ffGna7xE8)

Interestingly, if I remove the reference in foo argument type - it works.

Surprisingly the clang 12 from the LLVM windows bundle also works.


Regards,
Alex

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