It's ignored:
[C++11: 14.1/4]: A non-type template-parameter shall have one of the following (optionally cv-qualified) types:
- integral or enumeration type,
- pointer to object or pointer to function,
- lvalue reference to object or lvalue reference to function,
- pointer to member,
std::nullptr_t.
[C++11: 14.1/5]: [ Note: Other types are disallowed either explicitly below or implicitly by the rules governing the form of template-arguments (14.3). —end note ] The top-level cv-qualifiers on the template-parameter are ignored when determining its type.
The same wording is present at the same location in C++03.
This is partially because template arguments must be known at compile-time anyway. So, whether you have the const there or not, you may not pass some variable value:
template
void f()
{
N = 42;
}
template
void g()
{
N = 42;
}
int main()
{
f<0>();
g<0>();
static const int h = 1;
f();
g();
}
prog.cpp: In function ‘void f() [with int N = 0]’:
prog.cpp:15: instantiated from here
prog.cpp:4: error: lvalue required as left operand of assignment
prog.cpp: In function ‘void g() [with int N = 0]’:
prog.cpp:16: instantiated from here
prog.cpp:10: error: lvalue required as left operand of assignment
prog.cpp: In function ‘void f() [with int N = 1]’:
prog.cpp:19: instantiated from here
prog.cpp:4: error: lvalue required as left operand of assignment
prog.cpp: In function ‘void g() [with int N = 1]’:
prog.cpp:20: instantiated from here
prog.cpp:10: error: lvalue required as left operand of assignment
