+ /* Push enough of the current stack eagerly to */
+ /* ensure that callee-save registers saved in */
+ /* GC frames are scanned. */
+ /* In the non-threads case, schedule entire */
+ /* stack for scanning. */
+ /* The second argument is a pointer to the */
+ /* (possibly null) thread context, for */
+ /* (currently hypothetical) more precise */
+ /* stack scanning. */