glib uses __extension__ in macros dealing with 64 bits integer such as
GUINT64_SWAP_LE_BE().
To quote the GCC manual:
`-pedantic' and other options cause warnings for many GNU C extensions. You
can prevent such warnings within one expression by writing `__extension__'
before the expression.
https://bugzilla.gnome.org/show_bug.cgi?id=605779
expression
: assignment_expression
| expression ',' assignment_expression
+ | EXTENSION expression
{
$$ = gi_source_symbol_new (CSYMBOL_TYPE_INVALID);
}