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Spot potential UB #371

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jcoupey opened this issue Jul 30, 2020 · 2 comments · Fixed by #372
Closed

Spot potential UB #371

jcoupey opened this issue Jul 30, 2020 · 2 comments · Fixed by #372
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bug enhancement internals
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v1.8.0

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@jcoupey
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jcoupey commented Jul 30, 2020

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 jcoupey added this to the v1.8.0 milestone Jul 30, 2020
@jcoupey jcoupey mentioned this issue Jul 30, 2020
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@jcoupey
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jcoupey commented Jul 31, 2020

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

@jcoupey
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jcoupey commented Jul 31, 2020

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

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Fix UBSan error reports VROOM-Project/vroom
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