Tuesday coding tips are super short posts about various tidbits mainly from C++, but also from other programming languages I use. You can also follow the #TuesdayCodingTips hashtag on Mastodon and Linkedin.
C++ allows you to scrap your OS’ memory allocators, get yourself a huge chunk of memory and write your own allocators (they can be used with the standard library). It’s a hardcore optimization, but here’s a related tip that might be handy in normal projects as well.
When using the operator new, one can provide it with an already allocated memory, so it runs a constructor for a particular type in there. After that, reinterpret that memory as a pointer to your desired object and use it normally. However, deletion is a bit more complicated, as you have to call the destructor on that object manually (because delete must be called on the original memory, not the object).
// using some template type T
auto&& buffer = static_cast<std::byte*>(::operator new(sizeof(T)));
if (!buffer) throw std::bad_alloc();
new (buffer) T();
auto&& object = reinterpret_cast<T*>(buffer);
// ...
object->~T(); // call destructor
delete[] buffer; // properly release memory
I used this trick when implementing a resource manager that needs to hold any user data type (that is still default-constructible in my case): link