Disabling the Garbage Collector

In embedded environments, often you just can’t afford a garbage collector.

Note

Of course, if you use the current SDK without the GC, it will just leak through every hole That said, since there are many people interested in an SDK that doesn’t rely on the GC, we’ll do something about it. I’m thinking maybe version(!gc) {} blocks would be useful here.

Command line options

Step 1: use -gc=off to avoid linking with libgc

If you want to compile without the gc, use the -nogc compiler flag, e.g.

That way, it won’t try to link with libgc.

Note

Remember, to see what commands ooc launches, use the -v compiler option

Aliasing gc_malloc

Step 2: change the definitions of gc_[malloc, realloc, free] in sdk/ooclib.ooc

A good example of that is the ooc-ti project (for running

ooc applications on a TI89/92/v200 calculator), which uses a custom SDK with no GC.

Here’s the part of the sdk/ooclib.ooc file with memory allocation related definitions:

gc_malloc: extern(malloc) func (size: SizeT) -> Pointer
gc_malloc_atomic: extern(malloc) func (size: SizeT) -> Pointer
gc_realloc: extern(realloc) func (ptr: Pointer, size: SizeT) -> Pointer
gc_calloc: extern(calloc) func (nmemb: SizeT, size: SizeT) -> Pointer

As you can see, aliasing gc_malloc to malloc etc. is very easy and has no runtime cost (e.g. occurences of gc_malloc are just replaced with malloc)

Note

To use a custom sdk, specify its path by setting the OOC_SDK environment variable before launching ooc.

Step 3: PROFIT!

If you’re disabling the GC just to manual memory management, you may want to check out alternative malloc implementations, such as TCMalloc