[CExt] malloc vs ALLOC

thomthom

http://www.ruby-doc.org/docs/ProgrammingRuby/html/ext_ruby.html#S4

From that, it appear that Ruby Extension framework provides other methods of allocating memory. ALLOC_N, ALLOC, ALLOCA_N.

@unknownuser said:

You may sometimes need to allocate memory in an extension that won't be used for object storage---perhaps you've got a giant bitmap for a Bloom filter, or an image, or a whole bunch of little structures that Ruby doesn't use directly.

In order to work correctly with the garbage collector, you should use the following memory allocation routines. These routines do a little bit more work than the standard malloc. For instance, if ALLOC_N determines that it cannot allocate the desired amount of memory, it will invoke the garbage collector to try to reclaim some space. It will raise a NoMemError if it can't or if the requested amount of memory is invalid.

Is it that it's preferred to use these methods over malloc? For what purpose would I use these over malloc and free?

I also found this: http://zed.0xff.me/2010/01/17/you-must-free-memory-you-got-from-alloc-n-and-friends

@unknownuser said:

You MUST free memory you got from ALLOC_N & friends

So from the first link I got the impression that using ALLOC would make the GC take care of the data. But this second seem to indicate otherwise - which makes me wonder more on why I would use it.

I just made a test where I needed to make a dynamic C array to keep some data while doing calculations. I used malloc to create it and call free before I return. Would that be fine?