https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84489
Bug ID: 84489
Summary: Non-type template parameter dependency
Product: gcc
Version: 7.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: vince.rev at gmail dot com
Target Milestone: ---
Created attachment 43475
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43475&action=edit
Example code of the bug
Consider the following code in C++11.
=========================================================
#include <iostream>
template <class T = int, T N = T(), T B = (N >> 1)>
constexpr T f0() {return 0;}
template <class T = int, T N = T(), bool B = (N >> 1)>
constexpr T f1() {return 0;}
int main()
{
f0(); // No bug
f1(); // Bug here
return 0;
}
=========================================================
It compiles well under g++ 4.7, 4.8, 4.9, 5.X but fails to compile under 6.X
and 7.X. It also compiles well under clang. The returned error is:
=========================================================
gcc_bug_template_bool.cpp: In function 'int main()':
gcc_bug_template_bool.cpp:12:8: error: no matching function for call to 'f1()'
f1();
^
gcc_bug_template_bool.cpp:7:13: note: candidate: template<class T, T N, bool B>
constexpr T f1()
constexpr T f1() {return 0;}
^~
gcc_bug_template_bool.cpp:7:13: note: template argument
deduction/substitution failed:
gcc_bug_template_bool.cpp:6:49: error: invalid use of template type parameter
'T'
template <class T = int, T N = T(), bool B = (N >> 1)>
~~~^~~~~
gcc_bug_template_bool.cpp:6:53: error: could not convert template argument
'<expression error>' from '<type error>' to 'bool'
template <class T = int, T N = T(), bool B = (N >> 1)>
=========================================================
