https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80642
Bug ID: 80642
Summary: lambdas made constexpr in cases where they don't
satisfy the requirements for it
Product: gcc
Version: 7.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: mathias at gaunard dot com
Target Milestone: ---
Since C++17, lambdas are automatically constexpr whenever they can.
It seems however that GCC 7.1 tries to make lambdas constexpr in cases where it
actually can not.
Testcase, built with -std=c++1z
#include <array>
int main()
{
[](auto&& i)
{
if(i)
{
std::array<char, 4> array;
return i + array.size();
}
return i;
}(std::size_t(0));
}
Expected behaviour: everything compiles fine
What I get instead:
test.cpp: In instantiation of ‘main()::<lambda(auto:1&&)> [with auto:1 = long
unsigned int]’:
test.cpp:13:21: required from here
test.cpp:9:33: error: uninitialized variable ‘array’ in ‘constexpr’ function
std::array<char, 4> array;
^~~~~
In file included from test.cpp:1:0:
/usr/local/gcc-7.1.0/include/c++/7.1.0/array:94:12: note: ‘struct
std::array<char, 4>’ has no user-provided default constructor
struct array
^~~~~
/usr/local/gcc-7.1.0/include/c++/7.1.0/array:110:56: note: and the
implicitly-defined constructor does not initialize ‘char std::array<char,
4>::_M_elems [4]’
typename _AT_Type::_Type _M_elems;
^~~~~~~~
