[llvm-bugs] [Bug 37593] New: clang: diagnostics about constexpr misuse are nonexistant

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=37593

            Bug ID: 37593
           Summary: clang: diagnostics about constexpr misuse are
                    nonexistant
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Frontend
          Assignee: unassignedclangbugs at nondot.org
          Reporter: lebedev.ri at gmail.com
                CC: llvm-bugs at lists.llvm.org

https://godbolt.org/g/8jgtJU

struct A {
    struct B;
    static const B c;

    template <const B& d>
    static void theWork();
};

struct A::B {
    int e;
    explicit constexpr B(int e_) : e(e_) {}
};

constexpr auto A::c = A::B(0);

template <const A::B& d>
void A::theWork() {
    static_assert(d.e == 0, "can't stop the work!");
}

int main(int argc, char* argv[]) {
    A::theWork<A::c>();

    return 0;
}

clang happily accepts that code.
gcc chokes on it:

<source>:14:19: error: conflicting declaration 'constexpr const auto A::c'
 constexpr auto A::c = A::B(0);
                   ^
<source>:3:20: note: previous declaration as 'const A::B A::c'
     static const B c;
                    ^
<source>: In instantiation of 'static void A::theWork() [with const A::B& d =
A::c]':
<source>:22:22:   required from here
<source>:18:23: error: non-constant condition for static assertion
     static_assert(d.e == 0, "can't stop the work!");
                   ~~~~^~~~
<source>:18:23: error: the value of 'A::c' is not usable in a constant
expression
<source>:3:20: note: 'A::c' was not declared 'constexpr'
     static const B c;
                    ^
Compiler returned: 1

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20180525/48f0f124/attachment.html>