http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54430
Bug #: 54430
Summary: [C++11] Range Based For Loop lhs scoping issue
Classification: Unclassified
Product: gcc
Version: 4.7.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: [email protected]
ReportedBy: [email protected]
The scope of the iterating variable begins too early, i.e. it is already
available in the expression of the rhs.
This is a problem if the rhs expression includes the same identifier which is
shadowed by this issue.
Simple case:
int i[] = { };
for (int i : i);
fails to compile because the rhs 'i' will be the same as the lhs 'i' which is
not a valid expression for the range-based for-loop.
The range-based for-loop is equivalent to some for-construct. According to the
standard the above should compile because the scope of the lhs begins inside
the body of this substituted for-loop.
Just for completeness: The Evil case:
class MyType {
std::vector<MyType*> vec;
public:
const std::vector<MyType*>& foo() { return vec; }
};
MyType * t = new MyType;
for (MyType * t : t->foo());
this will not refuse to compile since everything is well-formed. The real
problem is that foo isn't called on the previously defined t but on the new
uninitialized t.
