Spot potential UB

[jcoupey]

Using GCC Undefined Behavior Sanitizer (enable by compiling with -fsanitize=undefined) on an instance of the Solomon benchmark results in:

/usr/include/c++/7/bits/stl_vector.h:816:34: runtime error: reference binding to null pointer of type 'const struct value_type'
structures/vroom/tw_route.cpp:453:43: runtime error: reference binding to null pointer of type 'const struct Break'

Because there is no break in input, the mentioned line:

vroom/src/structures/vroom/tw_route.cpp

Line 453 in b5dd59d

const auto& b = v.breaks[current_break];

defines a reference to the first element of an empty vector. In that case, the surrounding loop is designed in such a way that this reference is not actually used when the vector is empty, but this is still UB all right.

We should:

• investigate other potential runtime reports using other input examples
• fix spotted UB
• setup a way to check this periodically in the long run

No really sure how to go for that last point because setting -fsanitize=undefined slows down things to such a degree that it is totally not practically usable in dev mode.

[jcoupey]

Running across the usual academic/ad-hoc benchmarks, the error reported above is the only one we get.

[jcoupey]

For what it's worth, I also did a few checks raising no error with -fsanitize=address and -fsanitize=thread.