The following piece of C++ code:
template <typename T>
static void execute(T& obj) {
obj.template operator()<int>();
}
when compiled with IBM's xlC 11.1 results in the error message: 1540-0063 (S) The text "operator" is unexpected. If I use a function instead of an operator, it works fine, but I do not want to rewrite a lot of library code. Is there any other way how to make the .template operator construct work with xlC?
The best way to get the .template operator construct to work would be to submit a bug report to IBM.
This code conforms to the C++ standard. It is, in fact, the only legal way to write this code.
When you file the report you can use the following as evidence:
§14.2/4 states:
When the name of a member template specialization appears after . or -> in a postfix-expression ... and the object expression of the postfix-expression is type-dependent ... the member template name must be prefixed by the keyword template. ...
The first part: "the name of a member template specialization", applies because because operator()<int> is the name of a member template specialization. There is evidence for this in §14.2/1:
A template specialization can be referred to by a template-id:
§14.2/1 then specifies a syntax for a template-id which matches operator()<int>.
The second part: "and the object expression of the _postfix-expression_ is
type-dependent", applies because obj is type-dependent. obj is type-dependent because of §14.6.2.2/3:
An id-expression is type-dependent if it contains: - an identifier associated by name lookup with one or more declarations declared with a dependent type, ...
In this case, obj is associated with T&, which is a dependent type (because T is a template parameter).
This is only half of a definitive answer, as I have not provided references for many claims that I made. I have been at this for an hour now though, so it is probably time to stop.
