[Bug c++/69852] New: std::vector out of bounds access does not crash

["adtieni at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69852

            Bug ID: 69852
           Summary: std::vector out of bounds access does not crash
           Product: gcc
           Version: 5.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: adtieni at gmail dot com
  Target Milestone: ---

#include <iostream>
#include <string>
#include <vector>

int main() {
    std::vector<std::string> words(6);
    std::vector<std::string> words2;

    std::cout << "Before assignment: size " << words.size() << " capacity " <<
words.capacity() << std::endl;

    words = words2;

    std::cout << "After assignment: size " << words.size() << " capacity " <<
words.capacity() << std::endl;

    words[1] = "I should crash here";

    std::cout << "I did not crash. Words contains:" << std::endl;
    for (auto& el : words) {
        std::cout << el << ' ';
    }
}

Ran both
$ clang++ -v -std=c++14 -Wall -Wextra -pedantic -pthread test_vector.cpp
clang version 3.7.1 (tags/RELEASE_371/final)

$ g++ -v -std=c++14 -Wall -Wextra -pedantic -pthread test_vector.cpp
GNU C++14 (GCC) version 5.3.0 (x86_64-unknown-linux-gnu)


Outputs:

Before assignment: size 6 capacity 6
After assignment: size 0 capacity 6
I did not crash. Words contains: