Conversation

Nov 26, 2018

Any C++ experts in my timeline? Here's a problem: I have some code that uses a vector and references the start of the buffer with &v[0]. Seems to be common practice. However in some situations the vector is of size zero.

hanno

@hanno

Nov 26, 2018

So we end up having calls to functions that will reference the vector buffer as a target with an expected output size of zero. But UBSAN will throw warnings, which kinda makes sense: there is no v[0] in a vector of size zero.

hanno

@hanno

Nov 26, 2018

Is there any elegant solution beyond "if (size > 0) do this;"?

Daniel Micay

@DanielMicay

Replying to

@hanno

Using an iterator and comparing with end before using it. Using vec.begin() with a zero size array is fine though, just not dereferencing it since it already equals vec.end(). Maybe those functions should be getting passed a pair of iterators or a range, not a pointer and a size.

11:26 AM · Nov 26, 2018Twitter Web Client

Replying to

and

There's std::vector::data() instead of the &v[0] anti-pattern but using a pointer and pointer arithmetic to access a collection isn't idiomatic C++. Iterators are the old idiomatic style and ranges are the new modern style.