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darling-gdb/gdb/gnu-v3-abi.c
Andrew Cagney 3d499020f6 s/abort/gdb_assert/
2001-06-07 14:51:20 +00:00

356 lines
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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);
}
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