severity, summary changed

Markus Dreseler — Sat, 21 Jul 2018 15:19:17 GMT

severity Cosmetic → Problem
summary Documentation of monotonic_buffer_resource looks wrong → monotonic_buffer_resource current_buffer() possibly broken and documentation wrong

Looking at this again, it looks like current_buffer itself is also broken. Instead of returning a pointer to the start of the current buffer, it returns a pointer to where the next allocation should go:

// clang++ -std=c++1z -lboost_container mbr.cpp
#include <boost/container/pmr/monotonic_buffer_resource.hpp>
#include <boost/container/pmr/polymorphic_allocator.hpp>
#include <iostream>
int main() {
	auto buffer = boost::container::pmr::monotonic_buffer_resource(size_t{100});
	auto allocator = boost::container::pmr::polymorphic_allocator<char>{&buffer};
	allocator.allocate(1);
	auto start_ptr = buffer.current_buffer();
	allocator.allocate(50);
	auto end_ptr = buffer.current_buffer();
	std::cout << (reinterpret_cast<uintptr_t>(end_ptr) - reinterpret_cast<uintptr_t>(start_ptr)) << std::endl;
	// prints 50, but should be 0
}

Using clang 6.0 on OSX with boost 1.67.0_1.

Boost C++ Libraries: Ticket #13639: monotonic_buffer_resource current_buffer() possibly broken and documentation wrong

severity, summary changed