Size in Perl6 is not the same that the C one for : gumbo_element_s -- C size : 96 ; NC size : 104
Compiling a test file, this assume field name are the same
gumbo_element_s: GumboElement

For   HAS gumbo_vector_s children : c-size=16 / nc-size=16
For   has int32 tag : c-size=4 / nc-size=4
For   has int32 tag_namespace : c-size=4 / nc-size=4
For   HAS gumbo_string_piece_s original_tag : c-size=16 / nc-size=16
For   HAS gumbo_string_piece_s original_end_tag : c-size=16 / nc-size=16
For   HAS gumbo_source_position start_pos : c-size=12 / nc-size=12
For   HAS gumbo_source_position end_pos : c-size=12 / nc-size=12
For   HAS gumbo_vector_s attributes : c-size=16 / nc-size=16
Total C/NC sizes : 96/96
(skardev)root@pinkpony:~/p6/perl6-gumbo#