+/* --- Context operations -------------------------------------------------- */
+
+/* Remove sequences of BLOCKs having DB for stash, followed by a SUB context
+ * for the debugger callback. */
+
+STATIC I32 su_context_skip_db(pTHX_ I32 cxix) {
+#define su_context_skip_db(C) su_context_skip_db(aTHX_ (C))
+ I32 i;
+
+ if (!PL_DBsub)
+ return cxix;
+
+ for (i = cxix; i > 0; --i) {
+ PERL_CONTEXT *cx = cxstack + i;
+
+ switch (CxTYPE(cx)) {
+ case CXt_BLOCK:
+ if (cx->blk_oldcop && CopSTASH(cx->blk_oldcop) == GvSTASH(PL_DBgv))
+ continue;
+ break;
+ case CXt_SUB:
+ if (cx->blk_sub.cv == GvCV(PL_DBsub)) {
+ cxix = i - 1;
+ continue;
+ }
+ break;
+ default:
+ break;
+ }
+
+ break;
+ }
+
+ return cxix;
+}
+
+STATIC I32 su_context_up(pTHX_ I32 cxix) {
+#define su_context_up(C) su_context_up(aTHX_ (C))
+ PERL_CONTEXT *cx;
+
+ if (cxix <= 0)
+ return 0;
+
+ cx = cxstack + cxix;
+ if (CxTYPE(cx) == CXt_BLOCK) {
+ PERL_CONTEXT *prev = cx - 1;
+
+ switch (CxTYPE(prev)) {
+#if SU_HAS_PERL(5, 10, 0)
+ case CXt_GIVEN:
+ case CXt_WHEN:
+#endif
+#if SU_HAS_PERL(5, 11, 0)
+ /* That's the only subcategory that can cause an extra BLOCK context */
+ case CXt_LOOP_PLAIN:
+#else
+ case CXt_LOOP:
+#endif
+ if (cx->blk_oldcop == prev->blk_oldcop)
+ cxix -= 2;
+ else
+ --cxix;
+ break;
+ case CXt_SUBST:
+ if (cx->blk_oldcop && cx->blk_oldcop->op_sibling
+ && cx->blk_oldcop->op_sibling->op_type == OP_SUBST)
+ cxix -= 2;
+ else
+ --cxix;
+ break;
+ default:
+ --cxix;
+ break;
+ }
+ } else {
+ --cxix;
+ }
+
+ return cxix;
+}
+