xo-alloc/xo-refcnt/README.md

intrusive reference counting

Refcnt is a small shared library supplying intrusive reference counting.

Features

• base class ref::Refcounted. Application classes opt-in to reference counting by inheriting this class.
• common base simplifies connecting to common-base-object applications such as python, java etc.

Getting Started

build + install xo-cmake dependency (cmake macros)

see github/Rconybea/xo-cmake

Installs a few cmake ingredients, along with a build assistant for XO projects such as this one.

build + install XO deps

$ xo-build --clone --configure --build --install xo-indentlog

copy refcnt repository locally

$ xo-build --clone xo-refcnt

or equivalently

$ git clone git@github.com:Rconybea/refcnt.git xo-refcnt

build + install

$ xo-build --configure --build --install xo-refcnt

or equivalently:

$ mkdir xo-refcnt/.build
$ cmake -DCMAKE_INSTALL_PREFIX=${PREFIX} -S xo-refcnt -B xo-refcnt/.build
$ cmake --build xo-refcnt/.build
$ cmake --install xo-refcnt/.build

CMAKE_PREFIX_PATH should point to the prefix where xo-indentlog is installed

alternatively, if you're a nix user:

$ git clone git@github.com:rconybea/xo-nix.git
$ ls -d xo-nix
xo-nix
$ cd xo-nix
$ nix-build -A xo-refcnt

build for unit test coverage

$ cmake -DCMAKE_BUILD_TYPE=coverage -DCMAKE_PREFIX_PATH=${PREFIX} -S xo-refcnt -B xo-refcnt/.build-ccov
$ cmake --build xo-refcnt/.build-ccov

LSP support

$ cd xo-refcnt
$ ln -s build/compile_commands.json  # lsp will look for compile_commands.json in the root of the source tree

Examples

1

#include "xo/refcnt/Refcounted.hpp"

using xo::ref::Refcounted;

struct MyObject : public Refcounted {
     static rp<MyObject> make() { return new MyObject(); }

private:
     // intrusively-reference-counted objects should only be heap-allocated
     MyObject() { ... }
};

int main() {
     // create reference-counted instance
     auto x = MyObject::make();
     auto y = x;
     // x,y refer to the same instance.
     x = nullptr;
     // y holds last reference
     y = nullptr;
     // MyObject has been deleted
}

2

To log reference-counting activity

xo::ref::intrusive_ptr_set_debug(true);