Routines

This section describes some of the routines used in the C++ front-end.

build_vtable and prepare_fresh_vtable is used only within the `cp-class.c' file, and only in finish_struct and modify_vtable_entries.

build_vtable, prepare_fresh_vtable, and finish_struct are the only routines that set DECL_VPARENT.

finish_struct can steal the virtual function table from parents, this prohibits related_vslot from working. When finish_struct steals, we know that

get_binfo (DECL_FIELD_CONTEXT (CLASSTYPE_VFIELD (t)), t, 0)

will get the related binfo.

layout_basetypes does something with the VIRTUALS.

Supposedly (according to Tiemann) most of the breadth first searching done, like in get_base_distance and in get_binfo was not because of any design decision. I have since found out the at least one part of the compiler needs the notion of depth first binfo searching, I am going to try and convert the whole thing, it should just work. The term left-most refers to the depth first left-most node. It uses MAIN_VARIANT == type as the condition to get left-most, because the things that have BINFO_OFFSETs of zero are shared and will have themselves as their own MAIN_VARIANTs. The non-shared right ones, are copies of the left-most one, hence if it is its own MAIN_VARIANT, we know it IS a left-most one, if it is not, it is a non-left-most one.

get_base_distance's path and distance matters in its use in:

• prepare_fresh_vtable (the code is probably wrong)
• init_vfields Depends upon distance probably in a safe way, build_offset_ref might use partial paths to do further lookups, hack_identifier is probably not properly checking access.
• get_first_matching_virtual probably should check for get_base_distance returning -2.
• resolve_offset_ref should be called in a more deterministic manner. Right now, it is called in some random contexts, like for arguments at build_method_call time, default_conversion time, convert_arguments time, build_unary_op time, build_c_cast time, build_modify_expr time, convert_for_assignment time, and convert_for_initialization time. But, there are still more contexts it needs to be called in, one was the ever simple:

  if (obj.*pmi != 7)
     ...
  

  Seems that the problems were due to the fact that TREE_TYPE of the OFFSET_REF was not a OFFSET_TYPE, but rather the type of the referent (like INTEGER_TYPE). This problem was fixed by changing default_conversion to check TREE_CODE (x), instead of only checking TREE_CODE (TREE_TYPE (x)) to see if it was OFFSET_TYPE.

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