In tree.def:329 it is written that

 DECL_RESULT holds a RESULT_DECL node for the value of a function,
    or it is 0 for a function that returns no value.
    (C functions returning void have zero here.)

but C functions returning void have void_type_node in DECL_RESULT. Also note 
that allocate_struct_function calls aggregate_value_p on the DECL_RESULT and 
aggregate_value_p assumes that its argument is not null.

Should DECL_RESULT be allowed to be null or should the comment be fixed? If 
DECL_RESULT can be null, should aggregate_value_p return false if its 
argument is null? 

Thanks,
Rafael