https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95307
Daniel Krügler <daniel.kruegler at googlemail dot com> changed:
What |Removed |Added
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--- Comment #1 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
(In reply to Vincent Hamp from comment #0)
> The following snippet allows using reinterpret_casts inside a constexpr.
>
> #include <cstdint>
> uint64_t v;
> constexpr auto p{reinterpret_cast<uint64_t>(&v) - 1u};
>
> Compiled with GCC 10.1 and 9.3 with -std=c++2a
>
>
> Interestingly subtracting 0u results in an error.
Here a library-free variant of the code including the compiler flags used:
-Wall -Wextra -std=gnu++2a -pedantic
tested using gcc 11.0.0 20200522 (experimental):
//<<<<<<<<<<<<<<<<<<<<<
using uint64_t = unsigned long;
static_assert(sizeof(uint64_t) * 8 == 64);
uint64_t v;
constexpr auto p{reinterpret_cast<uint64_t>(&v) - 1u};
int main()
{
}
//>>>>>>>>>>>>>>>>>>>>>>>
The essential part of the reproducer is the fact that we have a variable of
static storage duration involved. Using a local variable in main() does make
the compiler reject the code.
