some fixes to the re2c change

configure.ac

@@ -67,7 +67,7 @@ AC_PROG_MAKE_SET
 
 AC_PATH_PROG(BZIP2_CMD, [bzip2])
 AC_PATH_PROG(RE2C_CMD, [re2c])
-AM_CONDITIONAL(HAVE_RE2C, test -n x"$RE2C_CMD")
+AM_CONDITIONAL(HAVE_RE2C, test x"$RE2C_CMD" != x"")
 
 AC_CHECK_SIZEOF(off_t)
 AC_CHECK_SIZEOF(size_t)

src/data_parser.hh

@@ -747,9 +747,12 @@ private:
 
         if (schema != NULL && this->dp_msg_format != NULL) {
             pcre_input &pi = this->dp_scanner->get_input();
-            pcre_context::capture_t last(this->dp_msg_format_begin, pi.pi_length);
+            if (this->dp_msg_format_begin < pi.pi_length) {
+                pcre_context::capture_t last(this->dp_msg_format_begin,
+                                             pi.pi_length);
 
-            *(this->dp_msg_format) += pi.get_substr(&last);
+                *(this->dp_msg_format) += pi.get_substr(&last);
+            }
         }
     };