Trying to fix the failing unit test

[soheilshahrouz]

I couldn't reproduce the unit test failure on a local machine, so I created this PR to trigger a CI run and hopefully locate the segault.

[AlexandreSinger]

@soheilshahrouz A suggestion which might make things easier is to increase the assert level for the unit test for your test and turning on the sanitizer so you can try and catch the bug in action.

Locally you can try building with:
CMAKE_PARAMS="-DVTR_ASSERT_LEVEL=3 -DVTR_ENABLE_SANITIZE=ON"
I set the assert level to 3, but you can increase it to 4 if you really want. I think the sanitizer will be the most help. It will slow things down tremendously, but since this is a unit test it should be pretty quick.

Edit:
The CI just does not seem to be consistent; so building and running locally may be better.

My guess is that this testcase has a memory leak; and specifically how the binary is built may change when it crashes and how (which explains why it crashes in different ways each time).

[vaughnbetz]

Suggest adding an example ...

[AlexandreSinger]

Hi, @soheilshahrouz , these changes LGTM.

My only comment is that I actually do not like the pairs() interface for a vector-like storage class. A vector is basically a contiguous array of values, where the index is not necessarily a part of the structure itself. The issue I see here is that you are generating the key of the pair when the iteration is happening; the key is not stored in the data structure directly. This is not going to be returned by reference (I think), or at least it really should not be since this is a reference to a temporary. I am not sure the performance impact of this. In my opinion the best way to iterate over a vector of values when you need the index as well as the value is to use a standard for loop.

Since this interface is optional to use though, I see no issue with adding it. But I do think it should be used sparingly (unless someone wants to dig into the assembly to see how this is being lowered lol).

[soheilshahrouz]

@vaughnbetz
Ready to be merged into master.