+/* --- Context operations -------------------------------------------------- */
+
+#if SU_HAS_PERL(5, 8, 9)
+# define SU_SKIP_DB_MAX 2
+#else
+# define SU_SKIP_DB_MAX 3
+#endif
+
+/* Skip context sequences of 1 to SU_SKIP_DB_MAX (included) block contexts
+ * followed by a DB sub */
+
+#define SU_SKIP_DB(C) \
+ STMT_START { \
+ I32 skipped = 0; \
+ PERL_CONTEXT *base = cxstack; \
+ PERL_CONTEXT *cx = base + (C); \
+ while (cx >= base && (C) > skipped && CxTYPE(cx) == CXt_BLOCK) \
+ --cx, ++skipped; \
+ if (cx >= base && (C) > skipped) { \
+ switch (CxTYPE(cx)) { \
+ case CXt_SUB: \
+ if (skipped <= SU_SKIP_DB_MAX && cx->blk_sub.cv == GvCV(PL_DBsub)) \
+ (C) -= skipped + 1; \
+ break; \
+ default: \
+ break; \
+ } \
+ } \
+ } STMT_END
+
+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;
+ }
+
+ if (PL_DBsub)
+ SU_SKIP_DB(cxix);
+
+ return cxix;
+}
+