Monday, January 19, 2009

Garbage collection - it's not about lazyness

There seems to be a common belief amongst a number of Delphi programmers (and c++ programmers etc) that garbage collection is all about being too lazy to do your own clean-up.

E.g. Babnik asks "What is it about Garbage Collection?" (kudos for actually asking the question) and his post has the implicit assumption that advocates are trying to avoid doing a bit of minor work.

Others have posted far more stronger comments (check the responses to Babnik's post) straight out stating that gc = lazyness, bad coding and a slack attitude to life. I find this attitude condescending and offensive. The reason I want gc, is not because I write bad code, but because i want to write better code.

I would like to see garbage collection in native Delphi, not as a mandatory feature, but as an option. It's not something I am holding my breath for, but if there was one thing I could add, that would be it.

I know I am repeating myself, but here are my main reasons for wanting a gc (expanded from an earlier post on the subject):

  • Better code: In a non gc language, you end up with a number of idioms and practices to guard against memory leaks. Delphi has several of these.
    It is rare to return an object from a function. Typically you would create an object and then pass it to a procedure to be modified.
    The use of assign rather than :=
    The use of Owner, Owned and the like to solve object destruction problems)

  • Less code: I performed a naive analysis on my most recent project by removing most .Free calls and the supporting destructors and try … finally blocks. The result was about 4% fewer lines of code. More importantly, the code I removed was boring, boilerplate which solved no business problems and added no value (other than preventing leaks)

  • Faster development: There are some minor time savings to be had simply by typing less code. However when I was regularly programming in c# I found my productivity improved due to the change of coding style that gc allowed.

  • Fewer memory leaks: By reducing the need for manually freeing memory, a gc significantly reduces the scope for memory leaks. It is still possible to leak memory, but much harder.
  • There are some problems that it is difficult to solve without a GC. Linq is often given as an example. Class operators (as opposed to record operators) is another
One of the main reasons I see for Delphi to have a gc, is that it's competitors have it. If we are to persuade people to write applications in Delphi as opposed to C#, Java etc then requiring manual memory is at best a speed bump.

Finally garbage collection definitely falls into the "Your kilometreage may vary" category. If you are working in memory constrained environments then manual management is the way to go. If you are writing database driven business apps or web apps (as I usually am) then manual management offers little or no advantage over a garbage collector.