Today when I took part in the Round #740 solving problem D. Top-Notch Insertions, my submission failed on test 2 without knowing why. After asserting I found that rope contains unwanted contents and I didn't fix the problem during the contest.

However, when I replace all __gnu_cxx::rope.erase(x) into __gnu_cxx::rope.erase(x, 1), my code works fine (idk if it will pass system test or not; at least, it passes asserting that all elements are rolled back to the initial state).

Then! I found it unbelievable to see the following code from here:

Look at the line 2318, comments: Erase, single character.

However, it calls erase(__p, __p + 1);, who will erase __p + 1 characters starting from the position __p.

I found it incredible since it's part of libstdc++. I don't know if there's a way to report such failure. Could anyone can tell me if I can do something with it? (or instead, NEVER USE SUCH FUNCTION IN THE FUTURE)

Thank you!