Context So I have a parser which can parse many different types of objects. I parse one file per object type using a function that has this typing: template <typename T> std::vector<T *> parseFeaturesfromFile(std::string) And when creating an object World, I use this function like this (in the constructor of World): const std::vector<C_type *> c_types ..
Category : allocator
I am reading some C++ code and specifically trying to understand a customised container. The container has following the template parameters: template<typename T, typename Alloc> class container{ … }; Where T is the type of data like float or int. The Alloc is the allocator and could be one of the standard libraries ones. Within ..
How can I use boost pool or some other similar allocator technique to allocate contiguous 512 byte sectors from a fixed block of memory. I am trying to emulate a memory filesystem in C++17. I assume that under the covers, when a user creates a new file of a specified length, a separate filesystem metadata ..
try { node = allocator.allocate(LIST_BASIC_UNIT); } catch (…) { allocator.deallocate(node); throw; } Should I call deallocator when an exception occurs in the STL allocator allocate? Source: Windows Que..
I’m implementing a basic std::vector by using an allocator, following PPP by Stroustrup, and in particular I’m sure that all the functions like resize, push_back, emplace_back, and so on are okay. What is really puzzling me a bit is the copy and move semantics: it works now, but I find it a bit too hard-coded ..
Autogenerated ROS (Robot Operating System) message C++ header files contain typedefs like this: typedef ::std_msgs::Header_<std::allocator<void> > Header; What does std::allocator<void> mean here? Why is the template type void? Here is the documentation for std::allocator<>: https://www.cplusplus.com/reference/memory/allocator/ https://en.cppreference.com/w/cpp/memory/allocator Here is the example autogenerated file to look at: http://docs.ros.org/en/electric/api/std_msgs/html/msg__gen_2cpp_2include_2std__msgs_2Header_8h_source.html. That first line above is line 116. This is ..
Suppose I have a custom stateful allocator that I want to use for a STL container. The container is going to use the rebind_alloc trait to allocate its internal elements, thus by default (or by defining rebind<T>::other), I can ask it to use my allocator class for the internals as well. However, I would like ..
I have the following toy code that works: #include <cstdlib> #include <vector> template <typename T> struct Dummy { using value_type = T; using size_type = size_t; using difference_type = ptrdiff_t; using pointer = value_type*; using const_pointer = const value_type*; using reference = value_type&; using const_reference = const value_type&; Dummy() = default; Dummy(const Dummy&) = default; ..
In a talk from 2015 Andrei Alexandrescu outlines some atrocities of the std::allocator interface, shortly highlighting how it’s not in fact about allocation and proposing a different way of thinking about these allocators that would make them more usable and modular. Or, to quote from the description: std::allocator has an inglorious past, murky present, and ..
I have started using pmr::allocators in my project, and I have seen a lot of performance boost and advantage from using them. I use allocator very similar to what I show int the simple example below: #include <array> #include <boost/container/flat_map.hpp> #include <cassert> #include <iostream> #include <memory_resource> #include <string> #include <vector> struct MessageBody { using map_t ..
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