https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110401
Bug ID: 110401
Summary: Unhelpful "goto is not a constant expression" in
ill-formed constexpr function template
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: xry111 at gcc dot gnu.org
Target Milestone: ---
#include <array>
template <int N>
constexpr std::array<int, N> get_sqr()
{
std::array<int, N> ret;
for (int i = 0; i < N; i++)
ret[i] = i * i;
return ret;
}
constexpr auto sqr = get_sqr<10000>();
GCC says "error: 'goto' is not a constant expression". This is puzzling
because there is no "goto" in the function.
Note that if it's not a template, GCC outputs the correct message:
#include <array>
constexpr std::array<int, 10000> get_sqr()
{
std::array<int, 10000> ret;
for (int i = 0; i < 10000; i++)
ret[i] = i * i;
return ret;
}
constexpr auto sqr = get_sqr();
t.cc: In function 'constexpr std::array<int, 10000> get_sqr()':
t.cc:5:28: error: uninitialized variable 'ret' in 'constexpr' function
5 | std::array<int, 10000> ret;
| ^~~
