+#ifdef PERL_IMPLICIT_CONTEXT
+
+/* implements the MY_CXT_INIT macro. The first time a module is loaded,
+the global PL_my_cxt_index is incremented, and that value is assigned to
+that module's static my_cxt_index (who's address is passed as an arg).
+Then, for each interpreter this function is called for, it makes sure a
+void* slot is available to hang the static data off, by allocating or
+extending the interpreter's PL_my_cxt_list array */
+
+void *
+Perl_my_cxt_init(pTHX_ int *index, size_t size)
+{
+ dVAR;
+ void *p;
+ if (*index == -1) {
+ /* this module hasn't been allocated an index yet */
+ MUTEX_LOCK(&PL_my_ctx_mutex);
+ *index = PL_my_cxt_index++;
+ MUTEX_UNLOCK(&PL_my_ctx_mutex);
+ }
+
+ /* make sure the array is big enough */
+ if (PL_my_cxt_size <= *index) {
+ if (PL_my_cxt_size) {
+ while (PL_my_cxt_size <= *index)
+ PL_my_cxt_size *= 2;
+ Renew(PL_my_cxt_list, PL_my_cxt_size, void *);
+ }
+ else {
+ PL_my_cxt_size = 16;
+ Newx(PL_my_cxt_list, PL_my_cxt_size, void *);
+ }
+ }
+ /* newSV() allocates one more than needed */
+ p = (void*)SvPVX(newSV(size-1));
+ PL_my_cxt_list[*index] = p;
+ Zero(p, size, char);
+ return p;
+}
+#endif
+