https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97388
Bug ID: 97388
Summary: constexpr evaluator incorrectly claims double delete
with function parameter
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: david at doublewise dot net
Target Milestone: ---
The following translation unit
```
struct S {
int * m_ptr;
constexpr S():
m_ptr(new int())
{
}
constexpr S(S && other) noexcept:
m_ptr(other.m_ptr)
{
other.m_ptr = nullptr;
}
constexpr ~S() noexcept {
delete m_ptr;
}
};
constexpr bool test(S v) {
auto x = static_cast<S &&>(v);
return true;
}
static_assert(test(S()));
```
is rejected with
```
<source>:23:19: error: non-constant condition for static assertion
23 | static_assert(test(S()));
| ~~~~^~~~~
Compiler returned: 1
```
This problem does not occur if `v` is turned into a local variable instead of a
function parameter.
The error message is also not helpful in this case. It gives a much more
helpful (but still erroneous) error message if `std::allocator` is used instead
of `new` and `delete`:
```
<source>:28:19: error: non-constant condition for static assertion
28 | static_assert(test(S()));
| ~~~~^~~~~
In file included from
/opt/compiler-explorer/gcc-trunk-20201012/include/c++/11.0.0/memory:64,
from <source>:1:
<source>:28:25: in 'constexpr' expansion of '(&<anonymous>)->S::~S()'
<source>:17:36: in 'constexpr' expansion of
'std::allocator<int>().std::allocator<int>::deallocate(((S*)this)->S::m_ptr,
1)'
/opt/compiler-explorer/gcc-trunk-20201012/include/c++/11.0.0/bits/allocator.h:183:30:
error: deallocation of already deallocated storage
183 | ::operator delete(__p);
| ~~~~~~~~~~~~~~~~~^~~~~
Compiler returned: 1
```
See it live: https://godbolt.org/z/hcv88h
