356 lines
12 KiB
C
356 lines
12 KiB
C
/* Abstraction of GNU v3 abi.
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Contributed by Jim Blandy <jimb@redhat.com>
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Copyright 2001 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#include "defs.h"
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#include "value.h"
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#include "cp-abi.h"
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#include "demangle.h"
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struct cp_abi_ops gnu_v3_abi_ops;
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static int
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gnuv3_is_vtable_name (const char *name)
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{
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return strncmp (name, "_ZTV", 4) == 0;
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}
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static int
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gnuv3_is_operator_name (const char *name)
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{
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return strncmp (name, "operator", 8) == 0;
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}
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/* To help us find the components of a vtable, we build ourselves a
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GDB type object representing the vtable structure. Following the
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V3 ABI, it goes something like this:
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struct gdb_gnu_v3_abi_vtable {
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/ * An array of virtual call and virtual base offsets. The real
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length of this array depends on the class hierarchy; we use
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negative subscripts to access the elements. Yucky, but
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better than the alternatives. * /
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ptrdiff_t vcall_and_vbase_offsets[0];
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/ * The offset from a virtual pointer referring to this table
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to the top of the complete object. * /
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ptrdiff_t offset_to_top;
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/ * The type_info pointer for this class. This is really a
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std::type_info *, but GDB doesn't really look at the
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type_info object itself, so we don't bother to get the type
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exactly right. * /
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void *type_info;
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/ * Virtual table pointers in objects point here. * /
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/ * Virtual function pointers. Like the vcall/vbase array, the
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real length of this table depends on the class hierarchy. * /
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void (*virtual_functions[0]) ();
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};
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The catch, of course, is that the exact layout of this table
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depends on the ABI --- word size, endianness, alignment, etc. So
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the GDB type object is actually a per-architecture kind of thing.
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vtable_type_gdbarch_data is a gdbarch per-architecture data pointer
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which refers to the struct type * for this structure, laid out
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appropriately for the architecture. */
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struct gdbarch_data *vtable_type_gdbarch_data;
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/* Human-readable names for the numbers of the fields above. */
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enum {
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vtable_field_vcall_and_vbase_offsets,
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vtable_field_offset_to_top,
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vtable_field_type_info,
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vtable_field_virtual_functions
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};
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/* Return a GDB type representing `struct gdb_gnu_v3_abi_vtable',
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described above, laid out appropriately for ARCH.
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We use this function as the gdbarch per-architecture data
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initialization function. We assume that the gdbarch framework
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calls the per-architecture data initialization functions after it
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sets current_gdbarch to the new architecture. */
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static void *
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build_gdb_vtable_type (struct gdbarch *arch)
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{
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struct type *t;
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struct field *field_list, *field;
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int offset;
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struct type *void_ptr_type
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= lookup_pointer_type (builtin_type_void);
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struct type *ptr_to_void_fn_type
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= lookup_pointer_type (lookup_function_type (builtin_type_void));
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/* ARCH can't give us the true ptrdiff_t type, so we guess. */
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struct type *ptrdiff_type
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= init_type (TYPE_CODE_INT, TARGET_PTR_BIT / TARGET_CHAR_BIT, 0,
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"ptrdiff_t", 0);
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/* We assume no padding is necessary, since GDB doesn't know
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anything about alignment at the moment. If this assumption bites
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us, we should add a gdbarch method which, given a type, returns
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the alignment that type requires, and then use that here. */
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/* Build the field list. */
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field_list = xmalloc (sizeof (struct field [4]));
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memset (field_list, 0, sizeof (struct field [4]));
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field = &field_list[0];
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offset = 0;
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/* ptrdiff_t vcall_and_vbase_offsets[0]; */
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FIELD_NAME (*field) = "vcall_and_vbase_offsets";
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FIELD_TYPE (*field)
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= create_array_type (0, ptrdiff_type,
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create_range_type (0, builtin_type_int, 0, -1));
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FIELD_BITPOS (*field) = offset * TARGET_CHAR_BIT;
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offset += TYPE_LENGTH (FIELD_TYPE (*field));
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field++;
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/* ptrdiff_t offset_to_top; */
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FIELD_NAME (*field) = "offset_to_top";
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FIELD_TYPE (*field) = ptrdiff_type;
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FIELD_BITPOS (*field) = offset * TARGET_CHAR_BIT;
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offset += TYPE_LENGTH (FIELD_TYPE (*field));
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field++;
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/* void *type_info; */
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FIELD_NAME (*field) = "type_info";
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FIELD_TYPE (*field) = void_ptr_type;
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FIELD_BITPOS (*field) = offset * TARGET_CHAR_BIT;
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offset += TYPE_LENGTH (FIELD_TYPE (*field));
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field++;
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/* void (*virtual_functions[0]) (); */
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FIELD_NAME (*field) = "virtual_functions";
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FIELD_TYPE (*field)
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= create_array_type (0, ptr_to_void_fn_type,
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create_range_type (0, builtin_type_int, 0, -1));
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FIELD_BITPOS (*field) = offset * TARGET_CHAR_BIT;
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offset += TYPE_LENGTH (FIELD_TYPE (*field));
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field++;
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/* We assumed in the allocation above that there were four fields. */
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if (field != field_list + 4)
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abort ();
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t = init_type (TYPE_CODE_STRUCT, offset, 0, 0, 0);
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TYPE_NFIELDS (t) = field - field_list;
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TYPE_FIELDS (t) = field_list;
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TYPE_TAG_NAME (t) = "gdb_gnu_v3_abi_vtable";
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return t;
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}
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/* Return the offset from the start of the imaginary `struct
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gdb_gnu_v3_abi_vtable' object to the vtable's "address point"
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(i.e., where objects' virtual table pointers point). */
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static int
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vtable_address_point_offset ()
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{
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struct type *vtable_type = gdbarch_data (vtable_type_gdbarch_data);
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return (TYPE_FIELD_BITPOS (vtable_type, vtable_field_virtual_functions)
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/ TARGET_CHAR_BIT);
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}
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static struct type *
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gnuv3_rtti_type (struct value *value,
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int *full_p, int *top_p, int *using_enc_p)
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{
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struct type *vtable_type = gdbarch_data (vtable_type_gdbarch_data);
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struct type *value_type = check_typedef (VALUE_TYPE (value));
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CORE_ADDR vtable_address;
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struct value *vtable;
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struct minimal_symbol *vtable_symbol;
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const char *vtable_symbol_name;
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const char *class_name;
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struct symbol *class_symbol;
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struct type *run_time_type;
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LONGEST offset_to_top;
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/* We only have RTTI for class objects. */
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if (TYPE_CODE (value_type) != TYPE_CODE_CLASS)
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return NULL;
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/* If we can't find the virtual table pointer for value_type, we
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can't find the RTTI. */
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fill_in_vptr_fieldno (value_type);
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if (TYPE_VPTR_FIELDNO (value_type) == -1)
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return NULL;
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/* Fetch VALUE's virtual table pointer, and tweak it to point at
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an instance of our imaginary gdb_gnu_v3_abi_vtable structure. */
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vtable_address
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= value_as_pointer (value_field (value, TYPE_VPTR_FIELDNO (value_type)));
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vtable = value_at_lazy (vtable_type,
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vtable_address - vtable_address_point_offset (),
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VALUE_BFD_SECTION (value));
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/* Find the linker symbol for this vtable. */
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vtable_symbol
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= lookup_minimal_symbol_by_pc (VALUE_ADDRESS (vtable)
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+ VALUE_OFFSET (vtable)
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+ VALUE_EMBEDDED_OFFSET (vtable));
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if (! vtable_symbol)
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return NULL;
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/* The symbol's demangled name should be something like "vtable for
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CLASS", where CLASS is the name of the run-time type of VALUE.
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If we didn't like this approach, we could instead look in the
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type_info object itself to get the class name. But this way
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should work just as well, and doesn't read target memory. */
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vtable_symbol_name = SYMBOL_DEMANGLED_NAME (vtable_symbol);
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if (strncmp (vtable_symbol_name, "vtable for ", 11))
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error ("can't find linker symbol for virtual table for `%s' value",
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TYPE_NAME (value_type));
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class_name = vtable_symbol_name + 11;
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/* Try to look up the class name as a type name. */
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class_symbol = lookup_symbol (class_name, 0, STRUCT_NAMESPACE, 0, 0);
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if (! class_symbol)
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error ("can't find class named `%s', as given by C++ RTTI", class_name);
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/* Make sure the type symbol is sane. (An earlier version of this
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code would find constructor functions, who have the same name as
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the class.) */
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if (SYMBOL_CLASS (class_symbol) != LOC_TYPEDEF
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|| TYPE_CODE (SYMBOL_TYPE (class_symbol)) != TYPE_CODE_CLASS)
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error ("C++ RTTI gives a class name of `%s', but that isn't a type name",
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class_name);
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/* This is the object's run-time type! */
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run_time_type = SYMBOL_TYPE (class_symbol);
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/* Get the offset from VALUE to the top of the complete object.
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NOTE: this is the reverse of the meaning of *TOP_P. */
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offset_to_top
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= value_as_long (value_field (vtable, vtable_field_offset_to_top));
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if (full_p)
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*full_p = (- offset_to_top == VALUE_EMBEDDED_OFFSET (value)
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&& (TYPE_LENGTH (VALUE_ENCLOSING_TYPE (value))
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>= TYPE_LENGTH (run_time_type)));
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if (top_p)
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*top_p = - offset_to_top;
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if (using_enc_p)
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*using_enc_p = 0;
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return run_time_type;
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}
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static struct value *
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gnuv3_virtual_fn_field (struct value **value_p,
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struct fn_field *f, int j,
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struct type *type, int offset)
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{
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struct type *vtable_type = gdbarch_data (vtable_type_gdbarch_data);
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struct value *value = *value_p;
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struct type *value_type = check_typedef (VALUE_TYPE (value));
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struct type *vfn_base;
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CORE_ADDR vtable_address;
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struct value *vtable;
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struct value *vfn;
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/* Some simple sanity checks. */
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if (TYPE_CODE (value_type) != TYPE_CODE_CLASS)
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error ("Only classes can have virtual functions.");
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/* Find the base class that defines this virtual function. */
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vfn_base = TYPE_FN_FIELD_FCONTEXT (f, j);
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if (! vfn_base)
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/* In programs compiled with G++ version 1, the debug info doesn't
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say which base class defined the virtual function. We'll guess
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it's the same base class that has our vtable; this is wrong for
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multiple inheritance, but it's better than nothing. */
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vfn_base = TYPE_VPTR_BASETYPE (type);
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/* This type may have been defined before its virtual function table
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was. If so, fill in the virtual function table entry for the
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type now. */
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if (TYPE_VPTR_FIELDNO (vfn_base) < 0)
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fill_in_vptr_fieldno (vfn_base);
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/* Now that we know which base class is defining our virtual
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function, cast our value to that baseclass. This takes care of
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any necessary `this' adjustments. */
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if (vfn_base != value_type)
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/* It would be nicer to simply cast the value to the appropriate
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base class (and I think that is supposed to be legal), but
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value_cast only does the right magic when casting pointers. */
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value = value_ind (value_cast (vfn_base, value_addr (value)));
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/* Now value is an object of the appropriate base type. Fetch its
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virtual table. */
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vtable_address
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= value_as_pointer (value_field (value, TYPE_VPTR_FIELDNO (vfn_base)));
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vtable = value_at_lazy (vtable_type,
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vtable_address - vtable_address_point_offset (),
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VALUE_BFD_SECTION (value));
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/* Fetch the appropriate function pointer from the vtable. */
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vfn = value_subscript (value_field (vtable, vtable_field_virtual_functions),
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value_from_longest (builtin_type_int,
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TYPE_FN_FIELD_VOFFSET (f, j)));
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/* Cast the function pointer to the appropriate type. */
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vfn = value_cast (lookup_pointer_type (TYPE_FN_FIELD_TYPE (f, j)),
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vfn);
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return vfn;
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}
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static void
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init_gnuv3_ops (void)
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{
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vtable_type_gdbarch_data = register_gdbarch_data (build_gdb_vtable_type, 0);
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gnu_v3_abi_ops.shortname = "gnu-v3";
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gnu_v3_abi_ops.longname = "GNU G++ Version 3 ABI";
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gnu_v3_abi_ops.doc = "G++ Version 3 ABI";
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gnu_v3_abi_ops.is_destructor_name = is_gnu_v3_mangled_dtor;
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gnu_v3_abi_ops.is_constructor_name = is_gnu_v3_mangled_ctor;
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gnu_v3_abi_ops.is_vtable_name = gnuv3_is_vtable_name;
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gnu_v3_abi_ops.is_operator_name = gnuv3_is_operator_name;
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gnu_v3_abi_ops.rtti_type = gnuv3_rtti_type;
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gnu_v3_abi_ops.virtual_fn_field = gnuv3_virtual_fn_field;
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}
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void
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_initialize_gnu_v3_abi (void)
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{
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init_gnuv3_ops ();
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register_cp_abi (gnu_v3_abi_ops);
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}
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