[RFC] Encoding of modes in module exports

[Jose E. Marchesi]

Yet another version with ga68_export.  The .ga68_exports section would
contain an array (with total size sh_size) of them.  To traverse the
table shall be fast, therefore the 'size' field in ga68_export.

Ok now I stop for some discussion on this approach :)

---

load elf;

type ga68_str = offset<Elf_Word,B>;
type ga68_text_reloc = Elf64_Addr;
type ga68_data_reloc = Elf64_Addr;

var GA68_EXPORT_MODE = 1;

var GA68_MODE_VOID = 0,
    GA68_MODE_INT = 1,
    GA68_MODE_REAL = 2,
    GA68_MODE_CHAR = 3,
    GA68_MODE_CMPL = 4,
    GA68_MODE_ROW = 5,
    GA68_MODE_STRUCT = 6,
    GA68_MODE_UNION = 7,
    GA68_MODE_NAME = 8,
    GA68_MOID = 9;

type ga68_mode =
  struct
  {
    Elf_Word kind;
    Elf_Word mode_kind;
    union
    {
      struct
      {
        ga68_text_reloc name;
        ga68_data_reloc mode;
      } moid : kind == GA68_MODE_MOID;

      struct
      {
        Elf_Word flex;
        ga68_data_reloc mode;
      } name : kind == GA68_MODE_NAME;

      struct
      {
        Elf_Word dim;
        struct { ga68_text_reloc lb; ga68_text_reloc ub; Elf64_Off stride; }[dim] triplets;
        ga68_data_reloc row_of;
      } row : kind == GA68_MODE_ROW;

      struct
      {
        Elf_Word nfields;
        struct { ga68_str name; ga68_data_reloc mode }[nfields] fields;
      } sct : kind == GA68_MODE_STRUCT;

      struct
      {
        Elf_Word nmodes;
        ga68_data_reloc[nmodes] modes;
      } uni : kind == GA68_MODE_UNION;

      struct {};
    } data;
  };

/* The contents of the .ga68_exports section can be mapped as a
   ga68_export[sec.sh_size] */

type ga68_export =
  struct
  {
    Elf64_Off size;
    union
    {
      ga68_mode mode;
    } export : export'size == size;
  };