hell.c

#include "libinternalevents.h"

st_table *object_counts;

void newobj_callback(VALUE tracepoint, void* data) {
    rb_trace_arg_t *trace_arg = rb_tracearg_from_tracepoint(tracepoint);

    st_data_t count = 0;

    VALUE obj   = rb_tracearg_object(trace_arg);
    VALUE klass = RBASIC_CLASS(obj);

    /* These aren't actually allocated so there's no point in tracking them. */
    if ( klass == Qtrue || klass == Qfalse || klass == Qnil ) {
        return;
    }

    st_lookup(object_counts, (st_data_t) klass, &count);
    st_insert(object_counts, (st_data_t) klass, count + 1);
}

void freeobj_callback(VALUE tracepoint, void* data) {
    rb_trace_arg_t *trace_arg = rb_tracearg_from_tracepoint(tracepoint);

    st_data_t count;

    VALUE obj   = rb_tracearg_object(trace_arg);
    VALUE klass = RBASIC_CLASS(obj);

    if ( st_lookup(object_counts, (st_data_t) klass, &count) ) {
        if ( count > 0 && (count - 1) > 0) {
            st_insert(object_counts, (st_data_t) klass, count - 1);
        }
        /* Remove the entry if the count is now 0 */
        else {
            st_delete(object_counts, (st_data_t*) &klass, NULL);
        }
    }
}

static int each_count(st_data_t key, st_data_t value, st_data_t hash_ptr) {
    VALUE rb_hash = (VALUE) hash_ptr;
    VALUE rb_key  = (VALUE) key;
    long count    = (long) value;

    rb_hash_aset(rb_hash, rb_key, INT2NUM(count));

    return ST_CONTINUE;
}

VALUE to_hash(VALUE self) {
    VALUE hash = rb_hash_new();

    st_foreach(object_counts, each_count, (st_data_t) hash);

    return hash;
}

void Init_libinternalevents() {
    VALUE new_tracer = rb_tracepoint_new(Qnil, RUBY_INTERNAL_EVENT_NEWOBJ,
                                         newobj_callback, NULL);

    VALUE free_tracer = rb_tracepoint_new(Qnil, RUBY_INTERNAL_EVENT_FREEOBJ,
                                          freeobj_callback, NULL);

    VALUE mInternalEvents = rb_define_module_under(rb_cObject, "InternalEvents");

    rb_define_singleton_method(mInternalEvents, "to_hash", to_hash, 0);

    object_counts = st_init_numtable();

    rb_tracepoint_enable(new_tracer);
    rb_tracepoint_enable(free_tracer);
}