https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104594
Bug ID: 104594
Summary: narrowing conversion of -1 to unsigned char at compile
time not detected
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: raffael at casagrande dot ch
Target Milestone: ---
The current gcc trunk compiles the following piece of code:
------------------------------------------------------------
template <unsigned char DIM_FROM>
concept Geometry = (DIM_FROM == -1);
template <class INIT>
requires Geometry<INIT::n>
auto GaussNewton(const INIT& init) -> void {}
template<int N>
struct X {
static constexpr int n = N;
};
int main() { GaussNewton(X<-1>{}); }
--------------------------------------
I think this should NOT compile since it entails a narrowing conversion of -1
to an unsigned char type at compile time. Clang as well as MSVC fail to compile
the code.
(In many other cases, gcc also fails to compile if such a narrowing conversion
happens at compile time.)
