[Boost-users] [Boost.CircularBuffer] begin()/end() arithmetic not working out quite right

Hi, Firstly, thanks for the work on a circular buffer. This is very useful since many of my applications require it. I am having a problem though... I am using Boost 1.38.0. When I call push_back(), the iterator math makes it appear that begin() moves backwards and end() remains constant. (Based on other STL libraries, I expect that begin() will remain constant and end() will keep advancing as I call push_back()). In other words, this assertion fails (but I expect it to succeed): circular_buffer<int> buf(8); circular_buffer<int>::iterator a; circular_buffer<int>::iterator b; a = buf.begin(); buf.push_back(1); b = buf.begin(); assert(a == b); // Fails!! Also, this code fails too (but I expect it to succeed): circular_buffer<int> buf(8); circular_buffer<int>::iterator a; circular_buffer<int>::iterator b; a = buf.end(); buf.push_back(1); b = buf.end(); assert(a != b); // Also fails! Below is a full example that you can compile and try out: #include #include int main () { typedef boost::circular_buffer<int> buf_type; // Instead of "end" moving ahead, "begin" is moving backwards when // // using "push_back". { buf_type buf1(1024); buf_type::iterator a; buf_type::iterator b; a = buf1.end(); buf1.push_back(1); buf1.push_back(2); b = buf1.end(); printf ("%d\n", a == b); // >>> // got: 1 // expected: 0 printf ("%d, %d\n", a-buf1.begin(), b-buf1.begin()); // >>> // got: 2, 2 // expected: 0, 2 } { buf_type buf2(1024); buf_type::iterator c; buf_type::iterator d; c = buf2.begin(); buf2.push_back(1); buf2.push_back(2); d = buf2.begin(); printf ("%d\n", c == d); // >>> // got: 0 // expected: 1 // (i.e. "begin()" is not still pointing to first item!! // This is incorrect, isn't it?) printf ("%d, %d\n", buf2.end()-c, buf2.end()-d); // >>> // got: 0, 2 // expected: 2, 2 } return 0; } Thanks, David