Question

Is there any chance for a call to std::vector<T>::clear() to throw an exception?

Answer 1

No.

[2003: 21.2.1/11 | n3290: 21.2.1/10]: Unless otherwise specified
(see 23.2.4.1, 23.2.5.1, 23.3.3.4, and 23.3.6.5) all container types
defined in this Clause meet the following additional requirements:
[..] — no erase(), clear(), pop_back() or pop_front()
function throws an exception. [..]

---

What happens if my element type destructor throws?

In C++11, std::vector<T>::clear() is marked noexcept ([n3290: 23.3.6/1]).

Any exceptions falling out of ~T could be caught by the implementation, so that clear() itself may not throw anything. If they’re not, and it does, the exception is “unexpected” and terminates the process rather than propagating:

struct T {
   ~T() { throw "lol"; }
};

int main() {
   try {
      vector<T> v{T()};
      v.clear();
   }
   catch (...) {
      cout << "caught";
   }
}

// Output: "terminated by exception: lol" (GCC 4.7.0 20111108)

[n3290: 15.5.1]: In some situations exception handling must be
abandoned for less subtle error handling techniques. [..] — when the
search for a handler (15.3) encounters the outermost block of a
function with a no-except-specification that does not allow the
exception (15.4) [..]