Are std::vector elements guaranteed to be contiguous?

Question

My question is simple: are std::vector elements guaranteed to be contiguous? In order word, can I use the pointer to the first element of a std::vector as a C-array?

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Answer 1

I found this thread because I have a use case where vectors using contiguous memory is an advantage.

I am learning how to use vertex buffer objects in OpenGL. I created a wrapper class to contain the buffer logic, so all I need to do is pass an array of floats and a few config values to create the buffer. I want to be able to generate a buffer from a function based on user input, so the length is not known at compile time. Doing something like this would be the easiest solution:

void generate(std::vector<float> v)
{
  float f = generate_next_float();
  v.push_back(f);
}

Now I can pass the vector's floats as an array to OpenGL's buffer-related functions. This also removes the need for sizeof to determine the length of the array.

This is far better than allocating a huge array to store the floats and hoping I made it big enough, or making my own dynamic array with contiguous storage.