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/* Abstraction of GNU v3 abi.

   Contributed by Jim Blandy <jimb@redhat.com>

   Copyright 2001 Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or

   modify it under the terms of the GNU General Public License as

   published by the Free Software Foundation; either version 2 of the

   License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program; if not, write to the Free Software

   Foundation, Inc., 59 Temple Place - Suite 330,

   Boston, MA 02111-1307, USA.  */

#include "defs.h"

#include "value.h"

#include "cp-abi.h"

#include "demangle.h"

#include "gdb_assert.h"

static struct cp_abi_ops gnu_v3_abi_ops;

static int

gnuv3_is_vtable_name (const char *name)

{

  return strncmp (name, "_ZTV", 4) == 0;

}

static int

gnuv3_is_operator_name (const char *name)

{

  return strncmp (name, "operator", 8) == 0;

}

/* To help us find the components of a vtable, we build ourselves a

   GDB type object representing the vtable structure.  Following the

   V3 ABI, it goes something like this:

   struct gdb_gnu_v3_abi_vtable {

     / * An array of virtual call and virtual base offsets.  The real

         length of this array depends on the class hierarchy; we use

         negative subscripts to access the elements.  Yucky, but

         better than the alternatives.  * /

     ptrdiff_t vcall_and_vbase_offsets[0];

     / * The offset from a virtual pointer referring to this table

         to the top of the complete object.  * /

     ptrdiff_t offset_to_top;

     / * The type_info pointer for this class.  This is really a

         std::type_info *, but GDB doesn't really look at the

         type_info object itself, so we don't bother to get the type

         exactly right.  * /

     void *type_info;

     / * Virtual table pointers in objects point here.  * /

     / * Virtual function pointers.  Like the vcall/vbase array, the

         real length of this table depends on the class hierarchy.  * /

     void (*virtual_functions[0]) ();

   };

   The catch, of course, is that the exact layout of this table

   depends on the ABI --- word size, endianness, alignment, etc.  So

   the GDB type object is actually a per-architecture kind of thing.

   vtable_type_gdbarch_data is a gdbarch per-architecture data pointer

   which refers to the struct type * for this structure, laid out

   appropriately for the architecture.  */

static struct gdbarch_data *vtable_type_gdbarch_data;

/* Human-readable names for the numbers of the fields above.  */

enum {

  vtable_field_vcall_and_vbase_offsets,

  vtable_field_offset_to_top,

  vtable_field_type_info,

  vtable_field_virtual_functions

};

/* Return a GDB type representing `struct gdb_gnu_v3_abi_vtable',

   described above, laid out appropriately for ARCH.

   We use this function as the gdbarch per-architecture data

   initialization function.  We assume that the gdbarch framework

   calls the per-architecture data initialization functions after it

   sets current_gdbarch to the new architecture.  */

static void *

build_gdb_vtable_type (struct gdbarch *arch)

{

  struct type *t;

  struct field *field_list, *field;

  int offset;

  struct type *void_ptr_type

    = lookup_pointer_type (builtin_type_void);

  struct type *ptr_to_void_fn_type

    = lookup_pointer_type (lookup_function_type (builtin_type_void));

  /* ARCH can't give us the true ptrdiff_t type, so we guess.  */

  struct type *ptrdiff_type

    = init_type (TYPE_CODE_INT, TARGET_PTR_BIT / TARGET_CHAR_BIT, 0,

                 "ptrdiff_t", 0);

  /* We assume no padding is necessary, since GDB doesn't know

     anything about alignment at the moment.  If this assumption bites

     us, we should add a gdbarch method which, given a type, returns

     the alignment that type requires, and then use that here.  */

  /* Build the field list.  */

  field_list = xmalloc (sizeof (struct field [4]));

  memset (field_list, 0, sizeof (struct field [4]));

  field = &field_list[0];

  offset = 0;

  /* ptrdiff_t vcall_and_vbase_offsets[0]; */

  FIELD_NAME (*field) = "vcall_and_vbase_offsets";

  FIELD_TYPE (*field)

    = create_array_type (0, ptrdiff_type,

                         create_range_type (0, builtin_type_int, 0, -1));

  FIELD_BITPOS (*field) = offset * TARGET_CHAR_BIT;

  offset += TYPE_LENGTH (FIELD_TYPE (*field));

  field++;

  /* ptrdiff_t offset_to_top; */

  FIELD_NAME (*field) = "offset_to_top";

  FIELD_TYPE (*field) = ptrdiff_type;

  FIELD_BITPOS (*field) = offset * TARGET_CHAR_BIT;

  offset += TYPE_LENGTH (FIELD_TYPE (*field));

  field++;

  /* void *type_info; */

  FIELD_NAME (*field) = "type_info";

  FIELD_TYPE (*field) = void_ptr_type;

  FIELD_BITPOS (*field) = offset * TARGET_CHAR_BIT;

  offset += TYPE_LENGTH (FIELD_TYPE (*field));

  field++;

  /* void (*virtual_functions[0]) (); */

  FIELD_NAME (*field) = "virtual_functions";

  FIELD_TYPE (*field)

    = create_array_type (0, ptr_to_void_fn_type,

                         create_range_type (0, builtin_type_int, 0, -1));

  FIELD_BITPOS (*field) = offset * TARGET_CHAR_BIT;

  offset += TYPE_LENGTH (FIELD_TYPE (*field));

  field++;

  /* We assumed in the allocation above that there were four fields.  */

  gdb_assert (field == (field_list + 4));

  t = init_type (TYPE_CODE_STRUCT, offset, 0, 0, 0);

  TYPE_NFIELDS (t) = field - field_list;

  TYPE_FIELDS (t) = field_list;

  TYPE_TAG_NAME (t) = "gdb_gnu_v3_abi_vtable";

  return t;

}

/* Return the offset from the start of the imaginary `struct

   gdb_gnu_v3_abi_vtable' object to the vtable's "address point"

   (i.e., where objects' virtual table pointers point).  */

static int

vtable_address_point_offset ()

{

  struct type *vtable_type = gdbarch_data (vtable_type_gdbarch_data);

  return (TYPE_FIELD_BITPOS (vtable_type, vtable_field_virtual_functions)

          / TARGET_CHAR_BIT);

}

static struct type *

gnuv3_rtti_type (struct value *value,

                 int *full_p, int *top_p, int *using_enc_p)

{

  struct type *vtable_type = gdbarch_data (vtable_type_gdbarch_data);

  struct type *value_type = check_typedef (VALUE_TYPE (value));

  CORE_ADDR vtable_address;

  struct value *vtable;

  struct minimal_symbol *vtable_symbol;

  const char *vtable_symbol_name;

  const char *class_name;

  struct symbol *class_symbol;

  struct type *run_time_type;

  LONGEST offset_to_top;

  /* We only have RTTI for class objects.  */

  if (TYPE_CODE (value_type) != TYPE_CODE_CLASS)

    return NULL;

  /* If we can't find the virtual table pointer for value_type, we

     can't find the RTTI.  */

  fill_in_vptr_fieldno (value_type);

  if (TYPE_VPTR_FIELDNO (value_type) == -1)

    return NULL;

  /* Fetch VALUE's virtual table pointer, and tweak it to point at

     an instance of our imaginary gdb_gnu_v3_abi_vtable structure.   */

  vtable_address

    = value_as_pointer (value_field (value, TYPE_VPTR_FIELDNO (value_type)));

  vtable = value_at_lazy (vtable_type,

                          vtable_address - vtable_address_point_offset (),

                          VALUE_BFD_SECTION (value));

  /* Find the linker symbol for this vtable.  */

  vtable_symbol

    = lookup_minimal_symbol_by_pc (VALUE_ADDRESS (vtable)

                                   + VALUE_OFFSET (vtable)

                                   + VALUE_EMBEDDED_OFFSET (vtable));

  if (! vtable_symbol)

    return NULL;

  /* The symbol's demangled name should be something like "vtable for

     CLASS", where CLASS is the name of the run-time type of VALUE.

     If we didn't like this approach, we could instead look in the

     type_info object itself to get the class name.  But this way

     should work just as well, and doesn't read target memory.  */

  vtable_symbol_name = SYMBOL_DEMANGLED_NAME (vtable_symbol);

  if (strncmp (vtable_symbol_name, "vtable for ", 11))

    error ("can't find linker symbol for virtual table for `%s' value",

           TYPE_NAME (value_type));

  class_name = vtable_symbol_name + 11;

  /* Try to look up the class name as a type name.  */

  class_symbol = lookup_symbol (class_name, 0, STRUCT_NAMESPACE, 0, 0);

  if (! class_symbol)

    error ("can't find class named `%s', as given by C++ RTTI", class_name);

  /* Make sure the type symbol is sane.  (An earlier version of this

     code would find constructor functions, who have the same name as

     the class.)  */

  if (SYMBOL_CLASS (class_symbol) != LOC_TYPEDEF

      || TYPE_CODE (SYMBOL_TYPE (class_symbol)) != TYPE_CODE_CLASS)

    error ("C++ RTTI gives a class name of `%s', but that isn't a type name",

           class_name);

  /* This is the object's run-time type!  */

  run_time_type = SYMBOL_TYPE (class_symbol);

  /* Get the offset from VALUE to the top of the complete object.

     NOTE: this is the reverse of the meaning of *TOP_P.  */

  offset_to_top

    = value_as_long (value_field (vtable, vtable_field_offset_to_top));

  if (full_p)

    *full_p = (- offset_to_top == VALUE_EMBEDDED_OFFSET (value)

               && (TYPE_LENGTH (VALUE_ENCLOSING_TYPE (value))

                   >= TYPE_LENGTH (run_time_type)));

  if (top_p)

    *top_p = - offset_to_top;

  if (using_enc_p)

    *using_enc_p = 0;

  return run_time_type;

}

static struct value *

gnuv3_virtual_fn_field (struct value **value_p,

                        struct fn_field *f, int j,

                        struct type *type, int offset)

{

  struct type *vtable_type = gdbarch_data (vtable_type_gdbarch_data);

  struct value *value = *value_p;

  struct type *value_type = check_typedef (VALUE_TYPE (value));

  struct type *vfn_base;

  CORE_ADDR vtable_address;

  struct value *vtable;

  struct value *vfn;

  /* Some simple sanity checks.  */

  if (TYPE_CODE (value_type) != TYPE_CODE_CLASS)

    error ("Only classes can have virtual functions.");

  /* Find the base class that defines this virtual function.  */

  vfn_base = TYPE_FN_FIELD_FCONTEXT (f, j);

  if (! vfn_base)

    /* In programs compiled with G++ version 1, the debug info doesn't

       say which base class defined the virtual function.  We'll guess

       it's the same base class that has our vtable; this is wrong for

       multiple inheritance, but it's better than nothing.  */

    vfn_base = TYPE_VPTR_BASETYPE (type);

  /* This type may have been defined before its virtual function table

     was.  If so, fill in the virtual function table entry for the

     type now.  */

  if (TYPE_VPTR_FIELDNO (vfn_base) < 0)

    fill_in_vptr_fieldno (vfn_base);

  /* Now that we know which base class is defining our virtual

     function, cast our value to that baseclass.  This takes care of

     any necessary `this' adjustments.  */

  if (vfn_base != value_type)

    /* It would be nicer to simply cast the value to the appropriate

       base class (and I think that is supposed to be legal), but

       value_cast only does the right magic when casting pointers.  */

    value = value_ind (value_cast (vfn_base, value_addr (value)));

  /* Now value is an object of the appropriate base type.  Fetch its

     virtual table.  */

  vtable_address

    = value_as_pointer (value_field (value, TYPE_VPTR_FIELDNO (vfn_base)));

  vtable = value_at_lazy (vtable_type,

                          vtable_address - vtable_address_point_offset (),

                          VALUE_BFD_SECTION (value));

  /* Fetch the appropriate function pointer from the vtable.  */

  vfn = value_subscript (value_field (vtable, vtable_field_virtual_functions),

                         value_from_longest (builtin_type_int,

                                             TYPE_FN_FIELD_VOFFSET (f, j)));

  /* Cast the function pointer to the appropriate type.  */

  vfn = value_cast (lookup_pointer_type (TYPE_FN_FIELD_TYPE (f, j)),

                    vfn);

  return vfn;

}

static void

init_gnuv3_ops (void)

{

  vtable_type_gdbarch_data = register_gdbarch_data (build_gdb_vtable_type, 0);

  gnu_v3_abi_ops.shortname = "gnu-v3";

  gnu_v3_abi_ops.longname = "GNU G++ Version 3 ABI";

  gnu_v3_abi_ops.doc = "G++ Version 3 ABI";

  gnu_v3_abi_ops.is_destructor_name = is_gnu_v3_mangled_dtor;

  gnu_v3_abi_ops.is_constructor_name = is_gnu_v3_mangled_ctor;

  gnu_v3_abi_ops.is_vtable_name = gnuv3_is_vtable_name;

  gnu_v3_abi_ops.is_operator_name = gnuv3_is_operator_name;

  gnu_v3_abi_ops.rtti_type = gnuv3_rtti_type;

  gnu_v3_abi_ops.virtual_fn_field = gnuv3_virtual_fn_field;

}

void

_initialize_gnu_v3_abi (void)

{

  init_gnuv3_ops ();

  register_cp_abi (gnu_v3_abi_ops);

}