From 7ed49443c244d7a9e911f013fcdd70306a349866 Mon Sep 17 00:00:00 2001 From: Jim Blandy Date: Tue, 22 May 2001 21:02:41 +0000 Subject: Add support for the GNU V3 C++ ABI. (Includes changes by Dan Berlin.) * gnu-v3-abi.c: New file. * minsyms.c: #include "value.h" and "cp-abi.h". (install_minimal_symbols): Check the minimal symbol table for symbols that look mangled in the V3 style, and select the V3 ABI if we find any. * Makefile.in (SFILES): Add gnu-v3-abi.c. (COMMON_OBS): Add gnu-v3-abi.o. (gnu-v3-abi.o): Add new rule. (minsyms.o): Depend on $(cp_abi_h) and $(value_h). --- gdb/gnu-v3-abi.c | 355 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 355 insertions(+) create mode 100644 gdb/gnu-v3-abi.c (limited to 'gdb/gnu-v3-abi.c') diff --git a/gdb/gnu-v3-abi.c b/gdb/gnu-v3-abi.c new file mode 100644 index 0000000..1bd4ce6 --- /dev/null +++ b/gdb/gnu-v3-abi.c @@ -0,0 +1,355 @@ +/* Abstraction of GNU v3 abi. + Contributed by Jim Blandy + 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" + +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. */ +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. */ + if (field != field_list + 4) + abort (); + + 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); +} -- cgit v1.1