This is the experimental C++ API for libpmemobj.

During the development of libpmemobj, many difficulties were encountered and compromises were made to make the C API as much user-friendly as possible. This is mostly due to the semantics of the C language. Since C++ is a more expressive language, it was natural to try and bridge the gap using native C++ features.

There are three main features of the C++ bindings:

the persistent_ptr<> smart pointer,
the transaction, which comes in two flavours - scoped and closure,
the p<> property.

The main issue with the C API is the generic PMEMoid and its typed counterpart, the TOID. For them to be conveniently used in transactions, a large set of macros has been defined. This made using the generic pointer easier, yet still unintuitive. In C++, the persistent_ptr<> template makes it a lot easier providing well known smart pointer semantics and built-in transactions support.

The other drawback of the C API is the transaction semantics. Manual usage of setjmp and jmpbuf is error prone, so they were once again wrapped in macros. They themselves have issues with undefined values of automatic variables (see the libpmemobj manpage for more details). The transactions defined in the C++ bindings try to fix the inadequacies of their C counterparts.

The p<>, which is called the persistent property, was designed with seamless persistent memory integration in mind. It is designed to be used with basic types within classes, to signify that these members in fact reside in persistent memory and need to be handled appropriately.

If you find any issues or have suggestion about these bindings please file an issue in https://github.com/pmem/issues. There are also blog articles in http://pmem.io/blog/ which you might find helpful.

Have fun! The NVML team

Compiler notice

The C++ bindings require a C++11 compliant compiler, therefore the minimal versions of GCC and Clang are 4.8.1 and 3.3 respectively. However the nvml::obj::transaction::automatic class requires C++17, so you need a more recent version for this to be available(GCC 6.1/Clang 3.7). It is recommended to use these or newer versions of GCC or Clang.

Important classes/functions

Transactional allocations - make_persistent.hpp
Transactional array allocations - make_persistent_array.hpp
Atomic allocations - make_persistent_atomic.hpp
Atomic array allocations - make_persistent_array_atomic.hpp
Resides on persistent memory property - p
Persistent smart pointer - persistent_ptr
Persistent memory transactions - transaction
Persistent memory resident mutex - mutex
Persistent memory pool - pool