https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68070
Bug ID: 68070
Summary: Undefined reference to default constructor of member
template class
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: frrrwww at gmail dot com
Target Milestone: ---
Hello,
When compiling the following simple program with `g++ prog.cc -Wall -Wextra
-std=c++14`
-----
#include <vector>
template<typename Value>
struct A
{
A() = default;
std::vector<Value> m_content;
};
void func(A<int> a = {})
{
}
int main()
{
func();
}
-----
We get the following error:
-----
/tmp/ccr6nbUo.o: In function `main':
prog.cc:(.text+0x1b): undefined reference to `std::vector<int,
std::allocator<int> >::vector()'
collect2: error: ld returned 1 exit status
-----
That error happens on gcc 4.9, 5.2 and 6.0, it does not happen on clang for
this specific code.
An alternative version of the code:
-----
#include <vector>
template<typename Value>
struct A
{
A() = default;
A(int) {}
std::vector<Value> m_content;
};
struct B { A<int> a; };
void func(B b = {})
{
}
int main()
{
func();
}
-----
gets this error:
-----
/tmp/ccvOFE5O.o: In function `main':
prog.cc:(.text+0x33): undefined reference to `A<int>::A()'
collect2: error: ld returned 1 exit status
-----
