http://llvm.org/bugs/show_bug.cgi?id=14855
Bug #: 14855
Summary: clang does not diagnose reference-to-member types
Product: clang
Version: trunk
Platform: All
OS/Version: All
Status: NEW
Severity: normal
Priority: P
Component: C++11
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected], [email protected]
Classification: Unclassified
There is no such thing as a reference-to-member type in C++. There is no syntax
for using them, no syntax for initializing them, and normally no syntax for
declaring them.
However with the following type aliases clang is perfectly happy to allow such
types to be created and used to a limited degree:
template<typename T>
using ref = T&;
template<typename T, typename C>
using mem = T C::;
Clang allows these reference-to-member types to be used like this:
#include <cstdio>
#include <type_traits>
struct S {
ref<mem<int,S>> x;
};
int main() {
std::printf("%i\n", (int)sizeof(S));
std::aligned_storage<S>::type X;
}
Additionally clang permits the mem type alias to be used in ways that it does
not permit for the equivalent member syntax:
struct S {};
mem<int, S> foo = 1;
int S::foo2 = 1; // error
int main() {
mem<int, S> foo3 = 3;
int S::foo4 = 4; // error
return foo3;
}
Clang treats these 'member' variables as though they are variables of type T.
int main() {
mem<int, S> foo;
int S::*foo2 = &foo; // error
}
error: cannot initialize a variable of type 'int S::*' with an rvalue of type
'mem<int, S> *' (aka 'int *')
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