https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70505
Bug ID: 70505
Summary: Constexpr failure when template type specified
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: vince.rev at gmail dot com
Target Milestone: ---
This bug seems to affect g++ 4.9, 5.1, 5.2, 5.3 and 6.0 (tested on
gcc.godbolt.org), while the same code compiles under g++ 4.7.3, 4.8.1 and 4.8.2
as well as under clang.
The code is the following:
=============================================
#include <iostream>
template <class X>
struct s
{
template <class T>
static constexpr T f1(const T x) {return x;}
template <class T, T = f1<T>(sizeof(T))>
static constexpr T f2(const T x) {return x;}
static void f() {s<int>::f2(42);}
};
int main()
{
s<int>::f();
}
=============================================
and the error is:
=============================================
main.cpp:10:39: error: no matching function for call to ‘s<int>::f2(int)’
static void f() {s<int>::f2(42);}
^
main.cpp:9:28: note: candidate: template<class T, T <anonymous> > static
constexpr T s<X>::f2(T) [with T = T; T <anonymous> = <enumerator>; X = int]
static constexpr T f2(const T x) {return x;}
^
main.cpp:9:28: note: template argument deduction/substitution failed:
main.cpp:8:47: error: expression ‘f1<int>’ is not a constant-expression
template <class T, T = f1<T>(sizeof(T))>
^
main.cpp:8:47: note: in template argument for type ‘int’
=============================================
The bug does not show up when the line n°8 is modified to:
=============================================
#include <iostream>
template <class X>
struct s
{
template <class T>
static constexpr T f1(const T x) {return x;}
template <class T, T = f1(sizeof(T))>
static constexpr T f2(const T x) {return x;}
static void f() {s<int>::f2(42);}
};
int main()
{
s<int>::f();
}
=============================================
