https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82657
Bug ID: 82657
Summary: when using a template function pointer as a non-type
template parameters, the template function will not be
defined in some situation
Product: gcc
Version: new-ra
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: niqiuha at gmail dot com
Target Milestone: ---
typedef bool(*func)(int);
//template<typename T = int>
//class TC1{
// public:
// static bool test_func(T t){
// return true;
// }
//};
template<typename T=int>
bool test_func(T){
return true;
}
template< func f = &test_func>
class TC2{
public:
TC2(){
//uncomment the line below ,compile will pass
//test_func(3);
f(3);
}
};
template<typename T = char>
class TC3{
public:
TC2<> mc;
TC3() = default;
};
int main(){
TC3<> tc3;
//uncomment the line below ,compile will pass
//TC2<> mc;
}
This piece of code compile ok on clang 7.3.0 , But fail to compile (
https://www.ideone.com/Dd092k ) on gcc 4.8.2, 5.2.0, 6.3 .
Gcc error information :
/tmp/ccW3jgBm.o: In function `TC2<&(bool test_func<int>(int))>::TC2()':
tempdef.cpp:(.text._ZN3TC2IXadL_Z9test_funcIiEbT_EEEC2Ev[_ZN3TC2IXadL_Z9test_funcIiEbT_EEEC5Ev]+0x12):
undefined reference to `bool test_func<int>(int)'
collect2: error: ld returned 1 exit status
I did some test , and found:
1. uncomment either line in code with special introduction will make this code
pass compile on gcc
2. change test_func from template function to static function of template
class, the error is same .
