I want to append a new value to a c++ std::vector and this new value is relative to the last value in the vector. Can this code result in undefined behaviour?
std::vector<int> vector;
vector.push_back(1);
vector.push_back(vector.back() + 1);
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Skipper HUN
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What specifically about this code are you concerned about? – François Andrieux May 28 '20 at 18:02
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@FrançoisAndrieux if the parameter of push_back is evaluated during the function call, it might try to read the value that is being appended to the vector. – Skipper HUN May 28 '20 at 18:07
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It [can be a problem](https://stackoverflow.com/questions/47253016/stdvectoremplace-back-bug-when-returning-references-c17) but not in this configuration. – François Andrieux May 28 '20 at 18:11
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The vector isn't empty, so you're not invoking undefined behavior because of that.
The parameter to push_back is fully evaluated before the call is made, so that's not undefined behavior either.
Mark Ransom
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For details about claim 2 see https://stackoverflow.com/a/4638386/5987. – Mark Ransom May 29 '20 at 16:03