// ------------------------------------
// Fields below are used during GC only
// During GC, if we are collecting this step, blocks and n_blocks
// are copied into the following two fields. After GC, these blocks
// are freed.
// ------------------------------------
// Fields below are used during GC only
// During GC, if we are collecting this step, blocks and n_blocks
// are copied into the following two fields. After GC, these blocks
// are freed.