This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 115e. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2024-11-11

49. Restriction on non-type, non-value template arguments

The example in 13.2 [temp.param] paragraph 8 is:

    template<int* a> struct R { /*...*/ };
    int* p;
    R<p> w;

I've been looking for the verbiage that specifies that this is an error and haven't found it. In particular, nothing in 13.2 [temp.param] ("Template parameters") nor 13.4.3 [temp.arg.nontype] ("Template non-type arguments") appears to rule out this case. (13.4.3 [temp.arg.nontype] paragraph 1 allows an argument to be "the name of an object or function with external linkage," with no limitation on the kinds of parameters such a name can match; "p" is, in fact, such a name.)

Should the resolution of the French comment include beefing up one or both of these sections to cover the applicable rules explicitly?

Proposed Resolution (04/99): Change the example in 13.2 [temp.param] paragraph 8 from:

    template<int *a> struct R { /* ... */ };
    template<int b[5]> struct S { /* ... */ };
    int *p;
    R<p> w; // OK
    S<p> x; // OK due to parameter adjustment
    int v[5];
    R<v> y; // OK due to implicit argument conversion
    S<v> z; // OK due to both adjustment and conversion

    template<int *a> struct R { /* ... */ };
    template<int b[5]> struct S { /* ... */ };
    int p;
    R<&p> w; // OK
    S<&p> x; // OK due to parameter adjustment
    int v[5];
    R<v> y; // OK due to implicit argument conversion
    S<v> z; // OK due to both adjustment and conversion

• the fourth bullet item should be changed from "...where the & is optional if the name refers to a function or array;" to "...where the & is optional if the name refers to a function or array, or if the corresponding template-parameter is a reference;"
• the third bullet item should be removed.