safe_range can consume all available memory on Python 2

[alekseyev]

safe_range has previously used xrange to get the length of a sequence.

    rng = xrange(*args)
    if len(rng) > MAX_RANGE:
        raise OverflowError('range too big, maximum size for range is %d' %
                            MAX_RANGE)

However since porting to Python 3 it uses range which behaves differently in Python 2 and 3. On Python 2 it will try to generate the whole sequence in memory before measuring the length -- which can cause an out of memory error.

---

Expected Behavior

safe_range(100000000000) should raise an OverflowError

Actual Behavior

safe_range(100000000000) attempts to generate a huge list in memory

Template Code

{%for n in range(100000000000) %}{{n}}{% endfor %}

Your Environment

• Python version: 2.7
• Jinja version: 2.10

[mitsuhiko]

Looks like this was an oversight on my part when I pulled in some Python 3 changes. This should be changed to use xrange again on 2.x