Use the return value from RE2::Set:Add to get the index of a set match.

src/vmod_re2.c

@@ -623,13 +623,12 @@ vmod_set_add(VRT_CTX, struct vmod_re2_set *set, VCL_STRING pattern,
 		     set->vcl_name, pattern, set->vcl_name);
 		return;
 	}
-	if ((err = vre2set_add(set->set, pattern)) != NULL) {
+	if ((err = vre2set_add(set->set, pattern, &n)) != NULL) {
 		VERR(ctx, ERR_PREFIX "Cannot compile '%.40s': %s",
 		     set->vcl_name, pattern, pattern, err);
 		return;
 	}
 
-	n = set->npatterns;
 	if (string != NULL) {
 		if ((set->string = realloc(set->string,
 					   (n + 1) * (sizeof(char *))))

src/vre2/vre2set.cpp

@@ -124,11 +124,11 @@ vre2set_init(vre2set **setp, anchor_e anchor, unsigned utf8,
 }
 
 const char *
-vre2set_add(vre2set *set, const char * const pattern)
+vre2set_add(vre2set *set, const char * const pattern, int * const idx)
 {
 	try {
 		string err;
-		if (set->add(pattern, &err) == -1)
+		if ((*idx = set->add(pattern, &err)) < 0)
 			throw runtime_error(err);
 		return NULL;
 	}

src/vre2/vre2set.h

@@ -69,7 +69,8 @@ extern "C" {
 				 unsigned case_sensitive, unsigned perl_classes,
 				 unsigned word_boundary, unsigned one_line);
 	const char *vre2set_fini(vre2set **vre2);
-	const char *vre2set_add(vre2set *set, const char *pattern);
+	const char *vre2set_add(vre2set *set, const char *pattern,
+				int * const idx);
 	const char *vre2set_compile(vre2set *set);
 	const char *vre2set_match(vre2set *set, const char *subject,
 				  int * const match, void *buf,