How does one specialize a template function to generate an error at compile-time if a user attempts to call said function with a given template parameter?
I was able to get this behavior for a template class by using the following idiom...
template <typename T>
class MyClass< std::vector<T> >;
The basic signature of the function which I am trying to modify is...
template <typename T>
T bar(const int arg) const {
...
}
If I use the same paradigm that I used to disallow certain template classes...
template<>
std::string foo::bar(const int arg) const;
I can generate a linker error, which I suppose is more desirable than a runtime error, but still not really what I'm looking for.
Since I am not able to use C++11, I cannot use static_assert, as described here. Instead, I am trying to use BOOST_STATIC_ASSERT like so...
template<>
std::string foo::bar(const int arg) const {
BOOST_STATIC_ASSERT(false);
return "";
}
However, this generates the following compile-time error, even when I am not trying to call an instance of the function with the template parameter I am attempting to disallow...
error: invalid application of 'sizeof' to incomplete type 'boost::STATIC_ASSERTION_FAILURE<false>'
I found this post, but it doesn't really offer any insight that I feel applies to me. Can anyone help?
Use boost::is_same to generate a compile-time boolean value that can then be used with BOOST_STATIC_ASSERT to perform the check.
template <typename T>
T bar(const int)
{
BOOST_STATIC_ASSERT_MSG((!boost::is_same<T, std::string>::value),
"T cannot be std::string");
return T();
}
bar<int>(10);
bar<std::string>(10); // fails static assertion