+#ifndef SCM_INLINE_C_INCLUDING_INLINE_H
+SCM_C_EXTERN_INLINE
+#endif
+SCM
+scm_immutable_double_cell (scm_t_bits car, scm_t_bits cbr,
+ scm_t_bits ccr, scm_t_bits cdr)
+{
+ SCM z;
+
+ z = SCM_PACK ((scm_t_bits) (GC_MALLOC_STUBBORN (2 * sizeof (scm_t_cell))));
+ /* Initialize the type slot last so that the cell is ignored by the
+ GC until it is completely initialized. This is only relevant
+ when the GC can actually run during this code, which it can't
+ since the GC only runs when all other threads are stopped.
+ */
+ SCM_GC_SET_CELL_WORD (z, 1, cbr);
+ SCM_GC_SET_CELL_WORD (z, 2, ccr);
+ SCM_GC_SET_CELL_WORD (z, 3, cdr);
+ SCM_GC_SET_CELL_WORD (z, 0, car);
+
+ GC_END_STUBBORN_CHANGE ((void *) z);
+
+ /* When this function is inlined, it's possible that the last
+ SCM_GC_SET_CELL_WORD above will be adjacent to a following
+ initialization of z. E.g., it occurred in scm_make_real. GCC
+ from around version 3 (e.g., certainly 3.2) began taking
+ advantage of strict C aliasing rules which say that it's OK to
+ interchange the initialization above and the one below when the
+ pointer types appear to differ sufficiently. We don't want that,
+ of course. GCC allows this behaviour to be disabled with the
+ -fno-strict-aliasing option, but would also need to be supplied
+ by Guile users. Instead, the following statements prevent the
+ reordering.
+ */