https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101295
Bug ID: 101295
Summary: constexpr destructor: ''result_decl' not supported by
dump_expr<expression error>' is not a constant
expression
Product: gcc
Version: 11.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: markus.kuehni at triviso dot ch
Target Milestone: ---
Trying to conceptualize a constexpr capable, optimizer friendly linked list
reference tracking smart pointer, I get this error:
<source>: In function 'int main()':
<source>:49:16: in 'constexpr' expansion of 'test()'
<source>:49:16: in 'constexpr' expansion of
'(&<anonymous>)->myptr<Obj>::~myptr()'
<source>:49:16: error: ''result_decl' not supported by dump_expr<expression
error>' is not a constant expression
49 | return test();
...
I'm not sure whether the code is standards compliant, but the error message is
broken anyway, it seems.
The same code works as I expect on clang, but creates an ICE on msvc. I tried
to create a minimal example that still shows the intention of the code.
https://godbolt.org/z/sod6oYE8T
```
// Minimized code of a linked list reference tracking smart pointer.
template<typename T>
struct myptr {
private:
T * p;
myptr * next;
public:
constexpr myptr(T * p) noexcept : p(p), next(p ? p->first : nullptr) {
if (p) {
p->first = this;
}
}
constexpr myptr(const myptr & other) noexcept : myptr(other.p) {}
constexpr ~myptr() noexcept {
if (p) {
myptr ** pnext = &(p->first);
while (*pnext != this) {
pnext = &((*pnext)->next);
}
*pnext = next;
next = nullptr;
if (!p->first) {
delete p;
}
p = nullptr;
}
}
};
struct Obj {
private:
struct myptr<Obj> * first{};
friend struct myptr<Obj>;
};
constexpr myptr<Obj> fun() {
myptr<Obj> obj(new Obj);
return obj;
}
// Force consteval to prove the myptr is constexpr capable.
consteval int test() {
fun();
return 42;
}
int main() {
return test();
}
```
