Compile-time constant for HEAP_GROWTH_FACTOR (patch attached)
The GC currently increases the size at which newly-created heaps by a factor of 1.8 for each heap. Some find it appropriate to modify this value (REE uses a value of 1 instead of 1.8, for example). In the trunk version of this code, that value is hard-coded in as a constant at 1.8 in gc.c:980.
I've included a patch to expose this as a compile-time constant (HEAP_GROW_FACTOR), and also included getters and setters in the style of the patch I submitted in Issue 1047: http://redmine.ruby-lang.org/issues/show/1047 .