+ /* A devious `function' could either:
+ - insert garbage into the list in front of us, causing XCDR to crash
+ - amputate the list behind us using (setcdr), causing the remaining
+ elts to lose their GCPRO status.
+
+ if (vals != 0) we avoid this by copying the elts into the
+ `vals' array. By a stroke of luck, `vals' is exactly large
+ enough to hold the elts left to be traversed as well as the
+ results computed so far.
+
+ if (vals == 0) we don't have any free space available and
+ don't want to eat up any more stack with alloca().
+ So we use EXTERNAL_LIST_LOOP_3 and GCPRO the tail. */
+
+ if (vals)