Are there examples for programming-languages support automatic management of resources besides memory?

Question

The idea of automatic memory management has gained big support with new programming languages. I'm interested if concepts exists for automatic management of other resources like files, network-sockets etc.?

Answer 1

For single threaded applications, the pattern of a resource being available for the extent of a block of code, with clean-up at the end, exists in several languages. Examples are the use of RAII in C++, or with-open-file in Common Lisp (and equivalent in newer Lisp-influenced languages - the same in Dylan, C#, Python and in Ruby you can pass a block to a file object).

I'm not aware of anything better suited for the multithreaded environments where modern garbage collection shines, short of combining RAII and reference counting or auto_ptr in C++, which isn't always a trivial combination.

One important distinction between automatic management of resources and automatic memory management is that memory management can often afford to be non-deterministic and only reclaimed when the process requires it, whereas often a resource is limited at an OS level, so should be reclaimed as soon as it is no longer used. Hence the choice of smart pointers rather than garbage collection as the management implementation. There's an intermediate level of resource - GDI objects, temporary file handles, threads - where an application wants to limit the total it uses, but doesn't care so much about releasing them to other processes - these are often pooled, which gets you some way towards automatic management.

Answer 2

One of the reasons we can automatically manage memory allocation now is we have so much of it.

Back in the days when memory was tight you had to squeeze the most out of every bite the system had.

Other resouces such as file handles and sockets are far fewer, and still need to be handled by hand (pun intended).

Consider also the .net compact framework, it’s not uncommon for windows mobile devices to have 32mb or 64mb of volatile memory to play with which - when you think about it - is still “lots”.

I wondering what the footprint of the .net compact framework is, and how would it perform on a Nokia phone with 4mb of volatile memory.

Anyone any ideas? (This is a wiki answer, feel free to correct or add more detail)

So, IMHIO we can afford to be slow reclaiming memory, because we're not going to run out of it in a hurry, which isn't the case with other resources.

Answer 3

perhaps you can look into boost::intrusive_ptr, where you take care of ref counting and deallocation

Answer 4

Object persistence and caching subsystems can be considered an automatic allocation of files and resources. If you apply a caching subsystem to a network connection you don't have to care about file opening, file deleting, and so on.

A way to manage automatically network connection could be done in parallel computing environment (i.e MPI), you can set programmatically the shape of the processors interconnections. Than you just send a message from a process to another, almost ignoring the way it's implemented. Sometimes those messages are translated in sockets.

If you have a function that let you get a page from its Url, would you consider it a sort of Automatic socket management?