add variable for clarity

src/vmod_re.c

@@ -206,6 +206,7 @@ backref(VRT_CTX, VCL_INT refnum, VCL_STRING fallback, struct vmod_priv *task)
 {
 	ov_t *ov;
 	char *substr;
+	const char *start;
 	int len;
 
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
@@ -234,11 +235,11 @@ backref(VRT_CTX, VCL_INT refnum, VCL_STRING fallback, struct vmod_priv *task)
 	if (ov->ovector[refnum] == -1)
 		return fallback;
 
+	start = ov->subject + ov->ovector[refnum];
 	len = ov->ovector[refnum+1] - ov->ovector[refnum];
 	assert(len <= ov->ovector[1] - ov->ovector[0]);
-	WS_Assert_Allocated(ctx->ws, ov->subject + ov->ovector[refnum], len);
-	substr = WS_Printf(ctx->ws, "%.*s", len,
-			   ov->subject + ov->ovector[refnum]);
+	WS_Assert_Allocated(ctx->ws, start, len);
+	substr = WS_Printf(ctx->ws, "%.*s", len, start);
 	if (substr == NULL) {
 		VSLb(ctx->vsl, SLT_VCL_Error,
 		     "vmod re: insufficient workspace");