Checking if a function has C-linkage at compile-time [unsolvable]
- by scjohnno
Is there any way to check if a given function is declared with C-linkage (that is, with extern "C") at compile-time?
I am developing a plugin system. Each plugin can supply factory functions to the plugin-loading code. However, this has to be done via name (and subsequent use of GetProcAddress or dlsym). This requires that the functions be declared with C-linkage so as to prevent name-mangling. It would be nice to be able to throw a compiler error if the referred-to function is declared with C++-linkage (as opposed to finding out at runtime when a function with that name does not exist).
Here's a simplified example of what I mean:
extern "C" void my_func()
{
}
void my_other_func()
{
}
// Replace this struct with one that actually works
template<typename T>
struct is_c_linkage
{
static const bool value = true;
};
template<typename T>
void assertCLinkage(T *func)
{
static_assert(is_c_linkage<T>::value, "Supplied function does not have C-linkage");
}
int main()
{
assertCLinkage(my_func); // Should compile
assertCLinkage(my_other_func); // Should NOT compile
}
Is there a possible implementation of is_c_linkage that would throw a compiler error for the second function, but not the first? I'm not sure that it's possible (though it may exist as a compiler extension, which I'd still like to know of). Thanks.
