cannot compile on ubuntu 19.04

[songmaotian]

download a 5.12.3 qt sdk, and using g++ to build the project, and get the following error

In file included from trace.cpp:3:
base.h:10:34: error: expected ‘,’ or ‘...’ before ‘default’
E to_enum(const QString &name, E default) {
^~~~~~~
base.h: In function ‘E xi::to_enum(const QString&, E)’:
base.h:17:12: error: expected primary-expression before ‘default’
return default;
^~~~~~~
base.h:17:11: error: expected ‘;’ before ‘default’
return default;
^~~~~~~~
;
base.h:17:12: error: case label not within a switch statement
return default;
^~~~~~~
base.h:17:19: error: expected ‘:’ before ‘;’ token
return default;
^
: