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binutils-gdb/gdb/gnu-v3-abi.c
Joel Brobecker 0fb0cc7590 Updated copyright notices for most files.
2009-01-03 05:58:08 +00:00

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/* Abstraction of GNU v3 abi.
Contributed by Jim Blandy <jimb@redhat.com>
Copyright (C) 2001, 2002, 2003, 2005, 2006, 2007, 2008, 2009
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 3 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, see <http://www.gnu.org/licenses/>. */
#include "defs.h"
#include "value.h"
#include "cp-abi.h"
#include "cp-support.h"
#include "demangle.h"
#include "objfiles.h"
#include "valprint.h"
#include "gdb_assert.h"
#include "gdb_string.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;
}
/* Determine architecture of class DOMAIN. This architecture is used
to query C++ ABI details (types, method pointer layout, etc.).
Note that we assume DOMAIN must have been allocated with an OBJFILE;
GDB does not provide any built-in class types. Thus we use the
architecture of that OBJFILE to define the C++ ABI. */
static struct gdbarch *
get_class_arch (struct type *domain)
{
gdb_assert (TYPE_CODE (domain) == TYPE_CODE_CLASS);
gdb_assert (TYPE_OBJFILE (domain) != NULL);
return get_objfile_arch (TYPE_OBJFILE (domain));
}
/* 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. */
static void *
build_gdb_vtable_type (struct gdbarch *arch)
{
struct type *t;
struct field *field_list, *field;
int offset;
struct type *void_ptr_type
= builtin_type (arch)->builtin_data_ptr;
struct type *ptr_to_void_fn_type
= builtin_type (arch)->builtin_func_ptr;
/* ARCH can't give us the true ptrdiff_t type, so we guess. */
struct type *ptrdiff_type
= init_type (TYPE_CODE_INT,
gdbarch_ptr_bit (arch) / 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_int32, 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_int32, 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 ptrdiff_t type used in the vtable type. */
static struct type *
vtable_ptrdiff_type (struct gdbarch *gdbarch)
{
struct type *vtable_type = gdbarch_data (gdbarch, vtable_type_gdbarch_data);
/* The "offset_to_top" field has the appropriate (ptrdiff_t) type. */
return TYPE_FIELD_TYPE (vtable_type, vtable_field_offset_to_top);
}
/* 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 gdbarch *gdbarch)
{
struct type *vtable_type = gdbarch_data (gdbarch, 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 gdbarch *gdbarch;
struct type *vtable_type;
struct type *values_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 type *run_time_type;
struct type *base_type;
LONGEST offset_to_top;
struct type *values_type_vptr_basetype;
int values_type_vptr_fieldno;
/* We only have RTTI for class objects. */
if (TYPE_CODE (values_type) != TYPE_CODE_CLASS)
return NULL;
/* This routine may be called for Java types that do not have
a proper objfile. Just return NULL for those. */
if (!TYPE_OBJFILE (values_type)
|| !TYPE_OBJFILE (values_type)->obfd)
return NULL;
/* Determine architecture. */
gdbarch = get_class_arch (values_type);
vtable_type = gdbarch_data (gdbarch, vtable_type_gdbarch_data);
/* If we can't find the virtual table pointer for values_type, we
can't find the RTTI. */
values_type_vptr_fieldno = get_vptr_fieldno (values_type,
&values_type_vptr_basetype);
if (values_type_vptr_fieldno == -1)
return NULL;
if (using_enc_p)
*using_enc_p = 0;
/* Fetch VALUE's virtual table pointer, and tweak it to point at
an instance of our imaginary gdb_gnu_v3_abi_vtable structure. */
base_type = check_typedef (values_type_vptr_basetype);
if (values_type != base_type)
{
value = value_cast (base_type, value);
if (using_enc_p)
*using_enc_p = 1;
}
vtable_address
= value_as_address (value_field (value, values_type_vptr_fieldno));
vtable
= value_at_lazy (vtable_type,
vtable_address - vtable_address_point_offset (gdbarch));
/* 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 (vtable_symbol_name == NULL
|| strncmp (vtable_symbol_name, "vtable for ", 11))
{
warning (_("can't find linker symbol for virtual table for `%s' value"),
TYPE_NAME (values_type));
if (vtable_symbol_name)
warning (_(" found `%s' instead"), vtable_symbol_name);
return NULL;
}
class_name = vtable_symbol_name + 11;
/* Try to look up the class name as a type name. */
/* FIXME: chastain/2003-11-26: block=NULL is bogus. See pr gdb/1465. */
run_time_type = cp_lookup_rtti_type (class_name, NULL);
if (run_time_type == NULL)
return NULL;
/* 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;
return run_time_type;
}
/* Find the vtable for CONTAINER and return a value of the correct
vtable type for this architecture. */
static struct value *
gnuv3_get_vtable (struct gdbarch *gdbarch, struct value *container)
{
struct type *vtable_type = gdbarch_data (gdbarch, vtable_type_gdbarch_data);
struct type *vtable_pointer_type;
struct value *vtable_pointer;
CORE_ADDR vtable_pointer_address, vtable_address;
/* We do not consult the debug information to find the virtual table.
The ABI specifies that it is always at offset zero in any class,
and debug information may not represent it. We won't issue an
error if there's a class with virtual functions but no virtual table
pointer, but something's already gone seriously wrong if that
happens.
We avoid using value_contents on principle, because the object might
be large. */
/* Find the type "pointer to virtual table". */
vtable_pointer_type = lookup_pointer_type (vtable_type);
/* Load it from the start of the class. */
vtable_pointer_address = value_as_address (value_addr (container));
vtable_pointer = value_at (vtable_pointer_type, vtable_pointer_address);
vtable_address = value_as_address (vtable_pointer);
/* Correct it to point at the start of the virtual table, rather
than the address point. */
return value_at_lazy (vtable_type,
vtable_address - vtable_address_point_offset (gdbarch));
}
/* Return a function pointer for CONTAINER's VTABLE_INDEX'th virtual
function, of type FNTYPE. */
static struct value *
gnuv3_get_virtual_fn (struct gdbarch *gdbarch, struct value *container,
struct type *fntype, int vtable_index)
{
struct value *vtable = gnuv3_get_vtable (gdbarch, container);
struct value *vfn;
/* Fetch the appropriate function pointer from the vtable. */
vfn = value_subscript (value_field (vtable, vtable_field_virtual_functions),
value_from_longest (builtin_type_int32, vtable_index));
/* If this architecture uses function descriptors directly in the vtable,
then the address of the vtable entry is actually a "function pointer"
(i.e. points to the descriptor). We don't need to scale the index
by the size of a function descriptor; GCC does that before outputing
debug information. */
if (gdbarch_vtable_function_descriptors (gdbarch))
vfn = value_addr (vfn);
/* Cast the function pointer to the appropriate type. */
vfn = value_cast (lookup_pointer_type (fntype), vfn);
return vfn;
}
/* GNU v3 implementation of value_virtual_fn_field. See cp-abi.h
for a description of the arguments. */
static struct value *
gnuv3_virtual_fn_field (struct value **value_p,
struct fn_field *f, int j,
struct type *vfn_base, int offset)
{
struct type *values_type = check_typedef (value_type (*value_p));
struct gdbarch *gdbarch;
/* Some simple sanity checks. */
if (TYPE_CODE (values_type) != TYPE_CODE_CLASS)
error (_("Only classes can have virtual functions."));
/* Determine architecture. */
gdbarch = get_class_arch (values_type);
/* Cast our value to the base class which defines this virtual
function. This takes care of any necessary `this'
adjustments. */
if (vfn_base != values_type)
*value_p = value_cast (vfn_base, *value_p);
return gnuv3_get_virtual_fn (gdbarch, *value_p, TYPE_FN_FIELD_TYPE (f, j),
TYPE_FN_FIELD_VOFFSET (f, j));
}
/* Compute the offset of the baseclass which is
the INDEXth baseclass of class TYPE,
for value at VALADDR (in host) at ADDRESS (in target).
The result is the offset of the baseclass value relative
to (the address of)(ARG) + OFFSET.
-1 is returned on error. */
static int
gnuv3_baseclass_offset (struct type *type, int index, const bfd_byte *valaddr,
CORE_ADDR address)
{
struct gdbarch *gdbarch;
struct type *vtable_type;
struct type *ptr_type;
struct value *vtable;
struct type *vbasetype;
struct value *offset_val, *vbase_array;
CORE_ADDR vtable_address;
long int cur_base_offset, base_offset;
int vbasetype_vptr_fieldno;
/* Determine architecture. */
gdbarch = get_class_arch (type);
vtable_type = gdbarch_data (gdbarch, vtable_type_gdbarch_data);
ptr_type = builtin_type (gdbarch)->builtin_data_ptr;
/* If it isn't a virtual base, this is easy. The offset is in the
type definition. */
if (!BASETYPE_VIA_VIRTUAL (type, index))
return TYPE_BASECLASS_BITPOS (type, index) / 8;
/* To access a virtual base, we need to use the vbase offset stored in
our vtable. Recent GCC versions provide this information. If it isn't
available, we could get what we needed from RTTI, or from drawing the
complete inheritance graph based on the debug info. Neither is
worthwhile. */
cur_base_offset = TYPE_BASECLASS_BITPOS (type, index) / 8;
if (cur_base_offset >= - vtable_address_point_offset (gdbarch))
error (_("Expected a negative vbase offset (old compiler?)"));
cur_base_offset = cur_base_offset + vtable_address_point_offset (gdbarch);
if ((- cur_base_offset) % TYPE_LENGTH (ptr_type) != 0)
error (_("Misaligned vbase offset."));
cur_base_offset = cur_base_offset / ((int) TYPE_LENGTH (ptr_type));
/* We're now looking for the cur_base_offset'th entry (negative index)
in the vcall_and_vbase_offsets array. We used to cast the object to
its TYPE_VPTR_BASETYPE, and reference the vtable as TYPE_VPTR_FIELDNO;
however, that cast can not be done without calling baseclass_offset again
if the TYPE_VPTR_BASETYPE is a virtual base class, as described in the
v3 C++ ABI Section 2.4.I.2.b. Fortunately the ABI guarantees that the
vtable pointer will be located at the beginning of the object, so we can
bypass the casting. Verify that the TYPE_VPTR_FIELDNO is in fact at the
start of whichever baseclass it resides in, as a sanity measure - iff
we have debugging information for that baseclass. */
vbasetype = TYPE_VPTR_BASETYPE (type);
vbasetype_vptr_fieldno = get_vptr_fieldno (vbasetype, NULL);
if (vbasetype_vptr_fieldno >= 0
&& TYPE_FIELD_BITPOS (vbasetype, vbasetype_vptr_fieldno) != 0)
error (_("Illegal vptr offset in class %s"),
TYPE_NAME (vbasetype) ? TYPE_NAME (vbasetype) : "<unknown>");
vtable_address = value_as_address (value_at_lazy (ptr_type, address));
vtable
= value_at_lazy (vtable_type,
vtable_address - vtable_address_point_offset (gdbarch));
offset_val = value_from_longest (builtin_type_int32, cur_base_offset);
vbase_array = value_field (vtable, vtable_field_vcall_and_vbase_offsets);
base_offset = value_as_long (value_subscript (vbase_array, offset_val));
return base_offset;
}
/* Locate a virtual method in DOMAIN or its non-virtual base classes
which has virtual table index VOFFSET. The method has an associated
"this" adjustment of ADJUSTMENT bytes. */
const char *
gnuv3_find_method_in (struct type *domain, CORE_ADDR voffset,
LONGEST adjustment)
{
int i;
const char *physname;
/* Search this class first. */
physname = NULL;
if (adjustment == 0)
{
int len;
len = TYPE_NFN_FIELDS (domain);
for (i = 0; i < len; i++)
{
int len2, j;
struct fn_field *f;
f = TYPE_FN_FIELDLIST1 (domain, i);
len2 = TYPE_FN_FIELDLIST_LENGTH (domain, i);
check_stub_method_group (domain, i);
for (j = 0; j < len2; j++)
if (TYPE_FN_FIELD_VOFFSET (f, j) == voffset)
return TYPE_FN_FIELD_PHYSNAME (f, j);
}
}
/* Next search non-virtual bases. If it's in a virtual base,
we're out of luck. */
for (i = 0; i < TYPE_N_BASECLASSES (domain); i++)
{
int pos;
struct type *basetype;
if (BASETYPE_VIA_VIRTUAL (domain, i))
continue;
pos = TYPE_BASECLASS_BITPOS (domain, i) / 8;
basetype = TYPE_FIELD_TYPE (domain, i);
/* Recurse with a modified adjustment. We don't need to adjust
voffset. */
if (adjustment >= pos && adjustment < pos + TYPE_LENGTH (basetype))
return gnuv3_find_method_in (basetype, voffset, adjustment - pos);
}
return NULL;
}
/* Decode GNU v3 method pointer. */
static int
gnuv3_decode_method_ptr (struct gdbarch *gdbarch,
const gdb_byte *contents,
CORE_ADDR *value_p,
LONGEST *adjustment_p)
{
struct type *funcptr_type = builtin_type (gdbarch)->builtin_func_ptr;
struct type *offset_type = vtable_ptrdiff_type (gdbarch);
CORE_ADDR ptr_value;
LONGEST voffset, adjustment;
int vbit;
/* Extract the pointer to member. The first element is either a pointer
or a vtable offset. For pointers, we need to use extract_typed_address
to allow the back-end to convert the pointer to a GDB address -- but
vtable offsets we must handle as integers. At this point, we do not
yet know which case we have, so we extract the value under both
interpretations and choose the right one later on. */
ptr_value = extract_typed_address (contents, funcptr_type);
voffset = extract_signed_integer (contents, TYPE_LENGTH (funcptr_type));
contents += TYPE_LENGTH (funcptr_type);
adjustment = extract_signed_integer (contents, TYPE_LENGTH (offset_type));
if (!gdbarch_vbit_in_delta (gdbarch))
{
vbit = voffset & 1;
voffset = voffset ^ vbit;
}
else
{
vbit = adjustment & 1;
adjustment = adjustment >> 1;
}
*value_p = vbit? voffset : ptr_value;
*adjustment_p = adjustment;
return vbit;
}
/* GNU v3 implementation of cplus_print_method_ptr. */
static void
gnuv3_print_method_ptr (const gdb_byte *contents,
struct type *type,
struct ui_file *stream)
{
struct type *domain = TYPE_DOMAIN_TYPE (type);
struct gdbarch *gdbarch = get_class_arch (domain);
CORE_ADDR ptr_value;
LONGEST adjustment;
int vbit;
/* Extract the pointer to member. */
vbit = gnuv3_decode_method_ptr (gdbarch, contents, &ptr_value, &adjustment);
/* Check for NULL. */
if (ptr_value == 0 && vbit == 0)
{
fprintf_filtered (stream, "NULL");
return;
}
/* Search for a virtual method. */
if (vbit)
{
CORE_ADDR voffset;
const char *physname;
/* It's a virtual table offset, maybe in this class. Search
for a field with the correct vtable offset. First convert it
to an index, as used in TYPE_FN_FIELD_VOFFSET. */
voffset = ptr_value / TYPE_LENGTH (vtable_ptrdiff_type (gdbarch));
physname = gnuv3_find_method_in (domain, voffset, adjustment);
/* If we found a method, print that. We don't bother to disambiguate
possible paths to the method based on the adjustment. */
if (physname)
{
char *demangled_name = cplus_demangle (physname,
DMGL_ANSI | DMGL_PARAMS);
if (demangled_name != NULL)
{
fprintf_filtered (stream, "&virtual ");
fputs_filtered (demangled_name, stream);
xfree (demangled_name);
return;
}
}
}
/* We didn't find it; print the raw data. */
if (vbit)
{
fprintf_filtered (stream, "&virtual table offset ");
print_longest (stream, 'd', 1, ptr_value);
}
else
print_address_demangle (ptr_value, stream, demangle);
if (adjustment)
{
fprintf_filtered (stream, ", this adjustment ");
print_longest (stream, 'd', 1, adjustment);
}
}
/* GNU v3 implementation of cplus_method_ptr_size. */
static int
gnuv3_method_ptr_size (struct type *type)
{
struct type *domain_type = check_typedef (TYPE_DOMAIN_TYPE (type));
struct gdbarch *gdbarch = get_class_arch (domain_type);
return 2 * TYPE_LENGTH (builtin_type (gdbarch)->builtin_data_ptr);
}
/* GNU v3 implementation of cplus_make_method_ptr. */
static void
gnuv3_make_method_ptr (struct type *type, gdb_byte *contents,
CORE_ADDR value, int is_virtual)
{
struct type *domain_type = check_typedef (TYPE_DOMAIN_TYPE (type));
struct gdbarch *gdbarch = get_class_arch (domain_type);
int size = TYPE_LENGTH (builtin_type (gdbarch)->builtin_data_ptr);
/* FIXME drow/2006-12-24: The adjustment of "this" is currently
always zero, since the method pointer is of the correct type.
But if the method pointer came from a base class, this is
incorrect - it should be the offset to the base. The best
fix might be to create the pointer to member pointing at the
base class and cast it to the derived class, but that requires
support for adjusting pointers to members when casting them -
not currently supported by GDB. */
if (!gdbarch_vbit_in_delta (gdbarch))
{
store_unsigned_integer (contents, size, value | is_virtual);
store_unsigned_integer (contents + size, size, 0);
}
else
{
store_unsigned_integer (contents, size, value);
store_unsigned_integer (contents + size, size, is_virtual);
}
}
/* GNU v3 implementation of cplus_method_ptr_to_value. */
static struct value *
gnuv3_method_ptr_to_value (struct value **this_p, struct value *method_ptr)
{
struct gdbarch *gdbarch;
const gdb_byte *contents = value_contents (method_ptr);
CORE_ADDR ptr_value;
struct type *domain_type, *final_type, *method_type;
LONGEST adjustment;
struct value *adjval;
int vbit;
domain_type = TYPE_DOMAIN_TYPE (check_typedef (value_type (method_ptr)));
final_type = lookup_pointer_type (domain_type);
method_type = TYPE_TARGET_TYPE (check_typedef (value_type (method_ptr)));
/* Extract the pointer to member. */
gdbarch = get_class_arch (domain_type);
vbit = gnuv3_decode_method_ptr (gdbarch, contents, &ptr_value, &adjustment);
/* First convert THIS to match the containing type of the pointer to
member. This cast may adjust the value of THIS. */
*this_p = value_cast (final_type, *this_p);
/* Then apply whatever adjustment is necessary. This creates a somewhat
strange pointer: it claims to have type FINAL_TYPE, but in fact it
might not be a valid FINAL_TYPE. For instance, it might be a
base class of FINAL_TYPE. And if it's not the primary base class,
then printing it out as a FINAL_TYPE object would produce some pretty
garbage.
But we don't really know the type of the first argument in
METHOD_TYPE either, which is why this happens. We can't
dereference this later as a FINAL_TYPE, but once we arrive in the
called method we'll have debugging information for the type of
"this" - and that'll match the value we produce here.
You can provoke this case by casting a Base::* to a Derived::*, for
instance. */
*this_p = value_cast (builtin_type (gdbarch)->builtin_data_ptr, *this_p);
adjval = value_from_longest (builtin_type (gdbarch)->builtin_long,
adjustment);
*this_p = value_ptradd (*this_p, adjval);
*this_p = value_cast (final_type, *this_p);
if (vbit)
{
LONGEST voffset;
voffset = ptr_value / TYPE_LENGTH (vtable_ptrdiff_type (gdbarch));
return gnuv3_get_virtual_fn (gdbarch, value_ind (*this_p),
method_type, voffset);
}
else
return value_from_pointer (lookup_pointer_type (method_type), ptr_value);
}
/* Determine if we are currently in a C++ thunk. If so, get the address
of the routine we are thunking to and continue to there instead. */
static CORE_ADDR
gnuv3_skip_trampoline (struct frame_info *frame, CORE_ADDR stop_pc)
{
CORE_ADDR real_stop_pc, method_stop_pc;
struct gdbarch *gdbarch = get_frame_arch (frame);
struct minimal_symbol *thunk_sym, *fn_sym;
struct obj_section *section;
char *thunk_name, *fn_name;
real_stop_pc = gdbarch_skip_trampoline_code (gdbarch, frame, stop_pc);
if (real_stop_pc == 0)
real_stop_pc = stop_pc;
/* Find the linker symbol for this potential thunk. */
thunk_sym = lookup_minimal_symbol_by_pc (real_stop_pc);
section = find_pc_section (real_stop_pc);
if (thunk_sym == NULL || section == NULL)
return 0;
/* The symbol's demangled name should be something like "virtual
thunk to FUNCTION", where FUNCTION is the name of the function
being thunked to. */
thunk_name = SYMBOL_DEMANGLED_NAME (thunk_sym);
if (thunk_name == NULL || strstr (thunk_name, " thunk to ") == NULL)
return 0;
fn_name = strstr (thunk_name, " thunk to ") + strlen (" thunk to ");
fn_sym = lookup_minimal_symbol (fn_name, NULL, section->objfile);
if (fn_sym == NULL)
return 0;
method_stop_pc = SYMBOL_VALUE_ADDRESS (fn_sym);
real_stop_pc = gdbarch_skip_trampoline_code
(gdbarch, frame, method_stop_pc);
if (real_stop_pc == 0)
real_stop_pc = method_stop_pc;
return real_stop_pc;
}
/* Return nonzero if a type should be passed by reference.
The rule in the v3 ABI document comes from section 3.1.1. If the
type has a non-trivial copy constructor or destructor, then the
caller must make a copy (by calling the copy constructor if there
is one or perform the copy itself otherwise), pass the address of
the copy, and then destroy the temporary (if necessary).
For return values with non-trivial copy constructors or
destructors, space will be allocated in the caller, and a pointer
will be passed as the first argument (preceding "this").
We don't have a bulletproof mechanism for determining whether a
constructor or destructor is trivial. For GCC and DWARF2 debug
information, we can check the artificial flag.
We don't do anything with the constructors or destructors,
but we have to get the argument passing right anyway. */
static int
gnuv3_pass_by_reference (struct type *type)
{
int fieldnum, fieldelem;
CHECK_TYPEDEF (type);
/* We're only interested in things that can have methods. */
if (TYPE_CODE (type) != TYPE_CODE_STRUCT
&& TYPE_CODE (type) != TYPE_CODE_CLASS
&& TYPE_CODE (type) != TYPE_CODE_UNION)
return 0;
for (fieldnum = 0; fieldnum < TYPE_NFN_FIELDS (type); fieldnum++)
for (fieldelem = 0; fieldelem < TYPE_FN_FIELDLIST_LENGTH (type, fieldnum);
fieldelem++)
{
struct fn_field *fn = TYPE_FN_FIELDLIST1 (type, fieldnum);
char *name = TYPE_FN_FIELDLIST_NAME (type, fieldnum);
struct type *fieldtype = TYPE_FN_FIELD_TYPE (fn, fieldelem);
/* If this function is marked as artificial, it is compiler-generated,
and we assume it is trivial. */
if (TYPE_FN_FIELD_ARTIFICIAL (fn, fieldelem))
continue;
/* If we've found a destructor, we must pass this by reference. */
if (name[0] == '~')
return 1;
/* If the mangled name of this method doesn't indicate that it
is a constructor, we're not interested.
FIXME drow/2007-09-23: We could do this using the name of
the method and the name of the class instead of dealing
with the mangled name. We don't have a convenient function
to strip off both leading scope qualifiers and trailing
template arguments yet. */
if (!is_constructor_name (TYPE_FN_FIELD_PHYSNAME (fn, fieldelem)))
continue;
/* If this method takes two arguments, and the second argument is
a reference to this class, then it is a copy constructor. */
if (TYPE_NFIELDS (fieldtype) == 2
&& TYPE_CODE (TYPE_FIELD_TYPE (fieldtype, 1)) == TYPE_CODE_REF
&& check_typedef (TYPE_TARGET_TYPE (TYPE_FIELD_TYPE (fieldtype, 1))) == type)
return 1;
}
/* Even if all the constructors and destructors were artificial, one
of them may have invoked a non-artificial constructor or
destructor in a base class. If any base class needs to be passed
by reference, so does this class. Similarly for members, which
are constructed whenever this class is. We do not need to worry
about recursive loops here, since we are only looking at members
of complete class type. */
for (fieldnum = 0; fieldnum < TYPE_NFIELDS (type); fieldnum++)
if (gnuv3_pass_by_reference (TYPE_FIELD_TYPE (type, fieldnum)))
return 1;
return 0;
}
static void
init_gnuv3_ops (void)
{
vtable_type_gdbarch_data = gdbarch_data_register_post_init (build_gdb_vtable_type);
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 =
(enum dtor_kinds (*) (const char *))is_gnu_v3_mangled_dtor;
gnu_v3_abi_ops.is_constructor_name =
(enum ctor_kinds (*) (const char *))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;
gnu_v3_abi_ops.baseclass_offset = gnuv3_baseclass_offset;
gnu_v3_abi_ops.print_method_ptr = gnuv3_print_method_ptr;
gnu_v3_abi_ops.method_ptr_size = gnuv3_method_ptr_size;
gnu_v3_abi_ops.make_method_ptr = gnuv3_make_method_ptr;
gnu_v3_abi_ops.method_ptr_to_value = gnuv3_method_ptr_to_value;
gnu_v3_abi_ops.skip_trampoline = gnuv3_skip_trampoline;
gnu_v3_abi_ops.pass_by_reference = gnuv3_pass_by_reference;
}
extern initialize_file_ftype _initialize_gnu_v3_abi; /* -Wmissing-prototypes */
void
_initialize_gnu_v3_abi (void)
{
init_gnuv3_ops ();
register_cp_abi (&gnu_v3_abi_ops);
}
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