old-cross-binutils/gdb/value.c

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/* Low level packing and unpacking of values for GDB, the GNU Debugger.
Copyright (C) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
1996, 1997, 1998, 1999, 2000, 2002, 2003, 2004, 2005, 2006, 2007, 2008
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 "gdb_string.h"
#include "symtab.h"
#include "gdbtypes.h"
#include "value.h"
#include "gdbcore.h"
#include "command.h"
#include "gdbcmd.h"
#include "target.h"
#include "language.h"
#include "demangle.h"
#include "doublest.h"
#include "gdb_assert.h"
#include "regcache.h"
#include "block.h"
#include "dfp.h"
#include "objfiles.h"
/* Prototypes for exported functions. */
void _initialize_values (void);
struct value
{
/* Type of value; either not an lval, or one of the various
different possible kinds of lval. */
enum lval_type lval;
/* Is it modifiable? Only relevant if lval != not_lval. */
int modifiable;
/* Location of value (if lval). */
union
{
/* If lval == lval_memory, this is the address in the inferior.
If lval == lval_register, this is the byte offset into the
registers structure. */
CORE_ADDR address;
/* Pointer to internal variable. */
struct internalvar *internalvar;
} location;
/* Describes offset of a value within lval of a structure in bytes.
If lval == lval_memory, this is an offset to the address. If
lval == lval_register, this is a further offset from
location.address within the registers structure. Note also the
member embedded_offset below. */
int offset;
/* Only used for bitfields; number of bits contained in them. */
int bitsize;
/* Only used for bitfields; position of start of field. For
gdbarch_bits_big_endian=0 targets, it is the position of the LSB. For
gdbarch_bits_big_endian=1 targets, it is the position of the MSB. */
int bitpos;
/* Frame register value is relative to. This will be described in
the lval enum above as "lval_register". */
struct frame_id frame_id;
/* Type of the value. */
struct type *type;
/* If a value represents a C++ object, then the `type' field gives
the object's compile-time type. If the object actually belongs
to some class derived from `type', perhaps with other base
classes and additional members, then `type' is just a subobject
of the real thing, and the full object is probably larger than
`type' would suggest.
If `type' is a dynamic class (i.e. one with a vtable), then GDB
can actually determine the object's run-time type by looking at
the run-time type information in the vtable. When this
information is available, we may elect to read in the entire
object, for several reasons:
- When printing the value, the user would probably rather see the
full object, not just the limited portion apparent from the
compile-time type.
- If `type' has virtual base classes, then even printing `type'
alone may require reaching outside the `type' portion of the
object to wherever the virtual base class has been stored.
When we store the entire object, `enclosing_type' is the run-time
type -- the complete object -- and `embedded_offset' is the
offset of `type' within that larger type, in bytes. The
value_contents() macro takes `embedded_offset' into account, so
most GDB code continues to see the `type' portion of the value,
just as the inferior would.
If `type' is a pointer to an object, then `enclosing_type' is a
pointer to the object's run-time type, and `pointed_to_offset' is
the offset in bytes from the full object to the pointed-to object
-- that is, the value `embedded_offset' would have if we followed
the pointer and fetched the complete object. (I don't really see
the point. Why not just determine the run-time type when you
indirect, and avoid the special case? The contents don't matter
until you indirect anyway.)
If we're not doing anything fancy, `enclosing_type' is equal to
`type', and `embedded_offset' is zero, so everything works
normally. */
struct type *enclosing_type;
int embedded_offset;
int pointed_to_offset;
/* Values are stored in a chain, so that they can be deleted easily
over calls to the inferior. Values assigned to internal
variables or put into the value history are taken off this
list. */
struct value *next;
/* Register number if the value is from a register. */
short regnum;
/* If zero, contents of this value are in the contents field. If
nonzero, contents are in inferior. If the lval field is lval_memory,
the contents are in inferior memory at location.address plus offset.
The lval field may also be lval_register.
WARNING: This field is used by the code which handles watchpoints
(see breakpoint.c) to decide whether a particular value can be
watched by hardware watchpoints. If the lazy flag is set for
some member of a value chain, it is assumed that this member of
the chain doesn't need to be watched as part of watching the
value itself. This is how GDB avoids watching the entire struct
or array when the user wants to watch a single struct member or
array element. If you ever change the way lazy flag is set and
reset, be sure to consider this use as well! */
char lazy;
/* If nonzero, this is the value of a variable which does not
actually exist in the program. */
char optimized_out;
/* If value is a variable, is it initialized or not. */
int initialized;
/* Actual contents of the value. For use of this value; setting it
uses the stuff above. Not valid if lazy is nonzero. Target
byte-order. We force it to be aligned properly for any possible
value. Note that a value therefore extends beyond what is
declared here. */
union
{
gdb_byte contents[1];
DOUBLEST force_doublest_align;
LONGEST force_longest_align;
CORE_ADDR force_core_addr_align;
void *force_pointer_align;
} aligner;
/* Do not add any new members here -- contents above will trash
them. */
};
/* Prototypes for local functions. */
static void show_values (char *, int);
static void show_convenience (char *, int);
/* The value-history records all the values printed
by print commands during this session. Each chunk
records 60 consecutive values. The first chunk on
the chain records the most recent values.
The total number of values is in value_history_count. */
#define VALUE_HISTORY_CHUNK 60
struct value_history_chunk
{
struct value_history_chunk *next;
struct value *values[VALUE_HISTORY_CHUNK];
};
/* Chain of chunks now in use. */
static struct value_history_chunk *value_history_chain;
static int value_history_count; /* Abs number of last entry stored */
/* List of all value objects currently allocated
(except for those released by calls to release_value)
This is so they can be freed after each command. */
static struct value *all_values;
/* Allocate a value that has the correct length for type TYPE. */
struct value *
allocate_value (struct type *type)
{
struct value *val;
struct type *atype = check_typedef (type);
val = (struct value *) xzalloc (sizeof (struct value) + TYPE_LENGTH (atype));
val->next = all_values;
all_values = val;
val->type = type;
val->enclosing_type = type;
VALUE_LVAL (val) = not_lval;
VALUE_ADDRESS (val) = 0;
VALUE_FRAME_ID (val) = null_frame_id;
val->offset = 0;
val->bitpos = 0;
val->bitsize = 0;
VALUE_REGNUM (val) = -1;
val->lazy = 0;
val->optimized_out = 0;
val->embedded_offset = 0;
val->pointed_to_offset = 0;
val->modifiable = 1;
val->initialized = 1; /* Default to initialized. */
return val;
}
/* Allocate a value that has the correct length
for COUNT repetitions of type TYPE. */
struct value *
allocate_repeat_value (struct type *type, int count)
{
int low_bound = current_language->string_lower_bound; /* ??? */
/* FIXME-type-allocation: need a way to free this type when we are
done with it. */
struct type *range_type
= create_range_type ((struct type *) NULL, builtin_type_int,
low_bound, count + low_bound - 1);
/* FIXME-type-allocation: need a way to free this type when we are
done with it. */
return allocate_value (create_array_type ((struct type *) NULL,
type, range_type));
}
/* Accessor methods. */
struct value *
value_next (struct value *value)
{
return value->next;
}
struct type *
value_type (struct value *value)
{
return value->type;
}
void
deprecated_set_value_type (struct value *value, struct type *type)
{
value->type = type;
}
int
value_offset (struct value *value)
{
return value->offset;
}
void
set_value_offset (struct value *value, int offset)
{
value->offset = offset;
}
int
value_bitpos (struct value *value)
{
return value->bitpos;
}
void
set_value_bitpos (struct value *value, int bit)
{
value->bitpos = bit;
}
int
value_bitsize (struct value *value)
{
return value->bitsize;
}
void
set_value_bitsize (struct value *value, int bit)
{
value->bitsize = bit;
}
gdb_byte *
value_contents_raw (struct value *value)
{
return value->aligner.contents + value->embedded_offset;
}
gdb_byte *
value_contents_all_raw (struct value *value)
{
return value->aligner.contents;
}
struct type *
value_enclosing_type (struct value *value)
{
return value->enclosing_type;
}
const gdb_byte *
value_contents_all (struct value *value)
{
if (value->lazy)
value_fetch_lazy (value);
return value->aligner.contents;
}
int
value_lazy (struct value *value)
{
return value->lazy;
}
void
set_value_lazy (struct value *value, int val)
{
value->lazy = val;
}
const gdb_byte *
value_contents (struct value *value)
{
return value_contents_writeable (value);
}
gdb_byte *
value_contents_writeable (struct value *value)
{
if (value->lazy)
value_fetch_lazy (value);
return value_contents_raw (value);
}
/* Return non-zero if VAL1 and VAL2 have the same contents. Note that
this function is different from value_equal; in C the operator ==
can return 0 even if the two values being compared are equal. */
int
value_contents_equal (struct value *val1, struct value *val2)
{
struct type *type1;
struct type *type2;
int len;
type1 = check_typedef (value_type (val1));
type2 = check_typedef (value_type (val2));
len = TYPE_LENGTH (type1);
if (len != TYPE_LENGTH (type2))
return 0;
return (memcmp (value_contents (val1), value_contents (val2), len) == 0);
}
int
value_optimized_out (struct value *value)
{
return value->optimized_out;
}
void
set_value_optimized_out (struct value *value, int val)
{
value->optimized_out = val;
}
int
value_embedded_offset (struct value *value)
{
return value->embedded_offset;
}
void
set_value_embedded_offset (struct value *value, int val)
{
value->embedded_offset = val;
}
int
value_pointed_to_offset (struct value *value)
{
return value->pointed_to_offset;
}
void
set_value_pointed_to_offset (struct value *value, int val)
{
value->pointed_to_offset = val;
}
enum lval_type *
deprecated_value_lval_hack (struct value *value)
{
return &value->lval;
}
CORE_ADDR *
deprecated_value_address_hack (struct value *value)
{
return &value->location.address;
}
struct internalvar **
deprecated_value_internalvar_hack (struct value *value)
{
return &value->location.internalvar;
}
struct frame_id *
deprecated_value_frame_id_hack (struct value *value)
{
return &value->frame_id;
}
short *
deprecated_value_regnum_hack (struct value *value)
{
return &value->regnum;
}
int
deprecated_value_modifiable (struct value *value)
{
return value->modifiable;
}
void
deprecated_set_value_modifiable (struct value *value, int modifiable)
{
value->modifiable = modifiable;
}
/* Return a mark in the value chain. All values allocated after the
mark is obtained (except for those released) are subject to being freed
if a subsequent value_free_to_mark is passed the mark. */
struct value *
value_mark (void)
{
return all_values;
}
/* Free all values allocated since MARK was obtained by value_mark
(except for those released). */
void
value_free_to_mark (struct value *mark)
{
struct value *val;
struct value *next;
for (val = all_values; val && val != mark; val = next)
{
next = val->next;
value_free (val);
}
all_values = val;
}
/* Free all the values that have been allocated (except for those released).
Called after each command, successful or not. */
void
free_all_values (void)
{
struct value *val;
struct value *next;
for (val = all_values; val; val = next)
{
next = val->next;
value_free (val);
}
all_values = 0;
}
/* Remove VAL from the chain all_values
so it will not be freed automatically. */
void
release_value (struct value *val)
{
struct value *v;
if (all_values == val)
{
all_values = val->next;
return;
}
for (v = all_values; v; v = v->next)
{
if (v->next == val)
{
v->next = val->next;
break;
}
}
}
/* Release all values up to mark */
struct value *
value_release_to_mark (struct value *mark)
{
struct value *val;
struct value *next;
for (val = next = all_values; next; next = next->next)
if (next->next == mark)
{
all_values = next->next;
next->next = NULL;
return val;
}
all_values = 0;
return val;
}
/* Return a copy of the value ARG.
It contains the same contents, for same memory address,
but it's a different block of storage. */
struct value *
value_copy (struct value *arg)
{
struct type *encl_type = value_enclosing_type (arg);
struct value *val = allocate_value (encl_type);
val->type = arg->type;
VALUE_LVAL (val) = VALUE_LVAL (arg);
val->location = arg->location;
val->offset = arg->offset;
val->bitpos = arg->bitpos;
val->bitsize = arg->bitsize;
VALUE_FRAME_ID (val) = VALUE_FRAME_ID (arg);
VALUE_REGNUM (val) = VALUE_REGNUM (arg);
val->lazy = arg->lazy;
val->optimized_out = arg->optimized_out;
val->embedded_offset = value_embedded_offset (arg);
val->pointed_to_offset = arg->pointed_to_offset;
val->modifiable = arg->modifiable;
if (!value_lazy (val))
{
memcpy (value_contents_all_raw (val), value_contents_all_raw (arg),
TYPE_LENGTH (value_enclosing_type (arg)));
}
return val;
}
/* Access to the value history. */
/* Record a new value in the value history.
Returns the absolute history index of the entry.
Result of -1 indicates the value was not saved; otherwise it is the
value history index of this new item. */
int
record_latest_value (struct value *val)
{
int i;
/* We don't want this value to have anything to do with the inferior anymore.
In particular, "set $1 = 50" should not affect the variable from which
the value was taken, and fast watchpoints should be able to assume that
a value on the value history never changes. */
if (value_lazy (val))
value_fetch_lazy (val);
/* We preserve VALUE_LVAL so that the user can find out where it was fetched
from. This is a bit dubious, because then *&$1 does not just return $1
but the current contents of that location. c'est la vie... */
val->modifiable = 0;
release_value (val);
/* Here we treat value_history_count as origin-zero
and applying to the value being stored now. */
i = value_history_count % VALUE_HISTORY_CHUNK;
if (i == 0)
{
struct value_history_chunk *new
= (struct value_history_chunk *)
xmalloc (sizeof (struct value_history_chunk));
memset (new->values, 0, sizeof new->values);
new->next = value_history_chain;
value_history_chain = new;
}
value_history_chain->values[i] = val;
/* Now we regard value_history_count as origin-one
and applying to the value just stored. */
return ++value_history_count;
}
/* Return a copy of the value in the history with sequence number NUM. */
struct value *
access_value_history (int num)
{
struct value_history_chunk *chunk;
int i;
int absnum = num;
if (absnum <= 0)
absnum += value_history_count;
if (absnum <= 0)
{
if (num == 0)
error (_("The history is empty."));
else if (num == 1)
error (_("There is only one value in the history."));
else
error (_("History does not go back to $$%d."), -num);
}
if (absnum > value_history_count)
error (_("History has not yet reached $%d."), absnum);
absnum--;
/* Now absnum is always absolute and origin zero. */
chunk = value_history_chain;
for (i = (value_history_count - 1) / VALUE_HISTORY_CHUNK - absnum / VALUE_HISTORY_CHUNK;
i > 0; i--)
chunk = chunk->next;
return value_copy (chunk->values[absnum % VALUE_HISTORY_CHUNK]);
}
static void
show_values (char *num_exp, int from_tty)
{
int i;
struct value *val;
static int num = 1;
if (num_exp)
{
/* "show values +" should print from the stored position.
"show values <exp>" should print around value number <exp>. */
if (num_exp[0] != '+' || num_exp[1] != '\0')
num = parse_and_eval_long (num_exp) - 5;
}
else
{
/* "show values" means print the last 10 values. */
num = value_history_count - 9;
}
if (num <= 0)
num = 1;
for (i = num; i < num + 10 && i <= value_history_count; i++)
{
val = access_value_history (i);
printf_filtered (("$%d = "), i);
value_print (val, gdb_stdout, 0, Val_pretty_default);
printf_filtered (("\n"));
}
/* The next "show values +" should start after what we just printed. */
num += 10;
/* Hitting just return after this command should do the same thing as
"show values +". If num_exp is null, this is unnecessary, since
"show values +" is not useful after "show values". */
if (from_tty && num_exp)
{
num_exp[0] = '+';
num_exp[1] = '\0';
}
}
/* Internal variables. These are variables within the debugger
that hold values assigned by debugger commands.
The user refers to them with a '$' prefix
that does not appear in the variable names stored internally. */
static struct internalvar *internalvars;
/* If the variable does not already exist create it and give it the value given.
If no value is given then the default is zero. */
static void
init_if_undefined_command (char* args, int from_tty)
{
struct internalvar* intvar;
/* Parse the expression - this is taken from set_command(). */
struct expression *expr = parse_expression (args);
register struct cleanup *old_chain =
make_cleanup (free_current_contents, &expr);
/* Validate the expression.
Was the expression an assignment?
Or even an expression at all? */
if (expr->nelts == 0 || expr->elts[0].opcode != BINOP_ASSIGN)
error (_("Init-if-undefined requires an assignment expression."));
/* Extract the variable from the parsed expression.
In the case of an assign the lvalue will be in elts[1] and elts[2]. */
if (expr->elts[1].opcode != OP_INTERNALVAR)
error (_("The first parameter to init-if-undefined should be a GDB variable."));
intvar = expr->elts[2].internalvar;
/* Only evaluate the expression if the lvalue is void.
This may still fail if the expresssion is invalid. */
if (TYPE_CODE (value_type (intvar->value)) == TYPE_CODE_VOID)
evaluate_expression (expr);
do_cleanups (old_chain);
}
/* Look up an internal variable with name NAME. NAME should not
normally include a dollar sign.
If the specified internal variable does not exist,
the return value is NULL. */
struct internalvar *
lookup_only_internalvar (char *name)
{
struct internalvar *var;
for (var = internalvars; var; var = var->next)
if (strcmp (var->name, name) == 0)
return var;
return NULL;
}
/* Create an internal variable with name NAME and with a void value.
NAME should not normally include a dollar sign. */
struct internalvar *
create_internalvar (char *name)
{
struct internalvar *var;
var = (struct internalvar *) xmalloc (sizeof (struct internalvar));
var->name = concat (name, (char *)NULL);
var->value = allocate_value (builtin_type_void);
var->endian = gdbarch_byte_order (current_gdbarch);
release_value (var->value);
var->next = internalvars;
internalvars = var;
return var;
}
/* Look up an internal variable with name NAME. NAME should not
normally include a dollar sign.
If the specified internal variable does not exist,
one is created, with a void value. */
struct internalvar *
lookup_internalvar (char *name)
{
struct internalvar *var;
var = lookup_only_internalvar (name);
if (var)
return var;
return create_internalvar (name);
}
struct value *
value_of_internalvar (struct internalvar *var)
{
struct value *val;
int i, j;
gdb_byte temp;
val = value_copy (var->value);
if (value_lazy (val))
value_fetch_lazy (val);
VALUE_LVAL (val) = lval_internalvar;
VALUE_INTERNALVAR (val) = var;
/* Values are always stored in the target's byte order. When connected to a
target this will most likely always be correct, so there's normally no
need to worry about it.
However, internal variables can be set up before the target endian is
known and so may become out of date. Fix it up before anybody sees.
Internal variables usually hold simple scalar values, and we can
correct those. More complex values (e.g. structures and floating
point types) are left alone, because they would be too complicated
to correct. */
if (var->endian != gdbarch_byte_order (current_gdbarch))
{
gdb_byte *array = value_contents_raw (val);
struct type *type = check_typedef (value_enclosing_type (val));
switch (TYPE_CODE (type))
{
case TYPE_CODE_INT:
case TYPE_CODE_PTR:
/* Reverse the bytes. */
for (i = 0, j = TYPE_LENGTH (type) - 1; i < j; i++, j--)
{
temp = array[j];
array[j] = array[i];
array[i] = temp;
}
break;
}
}
return val;
}
void
set_internalvar_component (struct internalvar *var, int offset, int bitpos,
int bitsize, struct value *newval)
{
gdb_byte *addr = value_contents_writeable (var->value) + offset;
if (bitsize)
modify_field (addr, value_as_long (newval),
bitpos, bitsize);
else
memcpy (addr, value_contents (newval), TYPE_LENGTH (value_type (newval)));
}
void
set_internalvar (struct internalvar *var, struct value *val)
{
struct value *newval;
newval = value_copy (val);
newval->modifiable = 1;
/* Force the value to be fetched from the target now, to avoid problems
later when this internalvar is referenced and the target is gone or
has changed. */
if (value_lazy (newval))
value_fetch_lazy (newval);
/* Begin code which must not call error(). If var->value points to
something free'd, an error() obviously leaves a dangling pointer.
But we also get a danling pointer if var->value points to
something in the value chain (i.e., before release_value is
called), because after the error free_all_values will get called before
long. */
xfree (var->value);
var->value = newval;
var->endian = gdbarch_byte_order (current_gdbarch);
release_value (newval);
/* End code which must not call error(). */
}
char *
internalvar_name (struct internalvar *var)
{
return var->name;
}
/* Update VALUE before discarding OBJFILE. COPIED_TYPES is used to
prevent cycles / duplicates. */
static void
preserve_one_value (struct value *value, struct objfile *objfile,
htab_t copied_types)
{
if (TYPE_OBJFILE (value->type) == objfile)
value->type = copy_type_recursive (objfile, value->type, copied_types);
if (TYPE_OBJFILE (value->enclosing_type) == objfile)
value->enclosing_type = copy_type_recursive (objfile,
value->enclosing_type,
copied_types);
}
/* Update the internal variables and value history when OBJFILE is
discarded; we must copy the types out of the objfile. New global types
will be created for every convenience variable which currently points to
this objfile's types, and the convenience variables will be adjusted to
use the new global types. */
void
preserve_values (struct objfile *objfile)
{
htab_t copied_types;
struct value_history_chunk *cur;
struct internalvar *var;
int i;
/* Create the hash table. We allocate on the objfile's obstack, since
it is soon to be deleted. */
copied_types = create_copied_types_hash (objfile);
for (cur = value_history_chain; cur; cur = cur->next)
for (i = 0; i < VALUE_HISTORY_CHUNK; i++)
if (cur->values[i])
preserve_one_value (cur->values[i], objfile, copied_types);
for (var = internalvars; var; var = var->next)
preserve_one_value (var->value, objfile, copied_types);
htab_delete (copied_types);
}
static void
show_convenience (char *ignore, int from_tty)
{
struct internalvar *var;
int varseen = 0;
for (var = internalvars; var; var = var->next)
{
if (!varseen)
{
varseen = 1;
}
printf_filtered (("$%s = "), var->name);
value_print (value_of_internalvar (var), gdb_stdout,
0, Val_pretty_default);
printf_filtered (("\n"));
}
if (!varseen)
printf_unfiltered (_("\
No debugger convenience variables now defined.\n\
Convenience variables have names starting with \"$\";\n\
use \"set\" as in \"set $foo = 5\" to define them.\n"));
}
/* Extract a value as a C number (either long or double).
Knows how to convert fixed values to double, or
floating values to long.
Does not deallocate the value. */
LONGEST
value_as_long (struct value *val)
{
/* This coerces arrays and functions, which is necessary (e.g.
in disassemble_command). It also dereferences references, which
I suspect is the most logical thing to do. */
val = coerce_array (val);
return unpack_long (value_type (val), value_contents (val));
}
DOUBLEST
value_as_double (struct value *val)
{
DOUBLEST foo;
int inv;
foo = unpack_double (value_type (val), value_contents (val), &inv);
if (inv)
error (_("Invalid floating value found in program."));
return foo;
}
/* Extract a value as a C pointer. Does not deallocate the value.
Note that val's type may not actually be a pointer; value_as_long
handles all the cases. */
CORE_ADDR
value_as_address (struct value *val)
{
/* Assume a CORE_ADDR can fit in a LONGEST (for now). Not sure
whether we want this to be true eventually. */
#if 0
/* gdbarch_addr_bits_remove is wrong if we are being called for a
non-address (e.g. argument to "signal", "info break", etc.), or
for pointers to char, in which the low bits *are* significant. */
return gdbarch_addr_bits_remove (current_gdbarch, value_as_long (val));
#else
/* There are several targets (IA-64, PowerPC, and others) which
don't represent pointers to functions as simply the address of
the function's entry point. For example, on the IA-64, a
function pointer points to a two-word descriptor, generated by
the linker, which contains the function's entry point, and the
value the IA-64 "global pointer" register should have --- to
support position-independent code. The linker generates
descriptors only for those functions whose addresses are taken.
On such targets, it's difficult for GDB to convert an arbitrary
function address into a function pointer; it has to either find
an existing descriptor for that function, or call malloc and
build its own. On some targets, it is impossible for GDB to
build a descriptor at all: the descriptor must contain a jump
instruction; data memory cannot be executed; and code memory
cannot be modified.
Upon entry to this function, if VAL is a value of type `function'
(that is, TYPE_CODE (VALUE_TYPE (val)) == TYPE_CODE_FUNC), then
VALUE_ADDRESS (val) is the address of the function. This is what
you'll get if you evaluate an expression like `main'. The call
to COERCE_ARRAY below actually does all the usual unary
conversions, which includes converting values of type `function'
to `pointer to function'. This is the challenging conversion
discussed above. Then, `unpack_long' will convert that pointer
back into an address.
So, suppose the user types `disassemble foo' on an architecture
with a strange function pointer representation, on which GDB
cannot build its own descriptors, and suppose further that `foo'
has no linker-built descriptor. The address->pointer conversion
will signal an error and prevent the command from running, even
though the next step would have been to convert the pointer
directly back into the same address.
The following shortcut avoids this whole mess. If VAL is a
function, just return its address directly. */
if (TYPE_CODE (value_type (val)) == TYPE_CODE_FUNC
|| TYPE_CODE (value_type (val)) == TYPE_CODE_METHOD)
return VALUE_ADDRESS (val);
val = coerce_array (val);
/* Some architectures (e.g. Harvard), map instruction and data
addresses onto a single large unified address space. For
instance: An architecture may consider a large integer in the
range 0x10000000 .. 0x1000ffff to already represent a data
addresses (hence not need a pointer to address conversion) while
a small integer would still need to be converted integer to
pointer to address. Just assume such architectures handle all
integer conversions in a single function. */
/* JimB writes:
I think INTEGER_TO_ADDRESS is a good idea as proposed --- but we
must admonish GDB hackers to make sure its behavior matches the
compiler's, whenever possible.
In general, I think GDB should evaluate expressions the same way
the compiler does. When the user copies an expression out of
their source code and hands it to a `print' command, they should
get the same value the compiler would have computed. Any
deviation from this rule can cause major confusion and annoyance,
and needs to be justified carefully. In other words, GDB doesn't
really have the freedom to do these conversions in clever and
useful ways.
AndrewC pointed out that users aren't complaining about how GDB
casts integers to pointers; they are complaining that they can't
take an address from a disassembly listing and give it to `x/i'.
This is certainly important.
Adding an architecture method like integer_to_address() certainly
makes it possible for GDB to "get it right" in all circumstances
--- the target has complete control over how things get done, so
people can Do The Right Thing for their target without breaking
anyone else. The standard doesn't specify how integers get
converted to pointers; usually, the ABI doesn't either, but
ABI-specific code is a more reasonable place to handle it. */
if (TYPE_CODE (value_type (val)) != TYPE_CODE_PTR
&& TYPE_CODE (value_type (val)) != TYPE_CODE_REF
&& gdbarch_integer_to_address_p (current_gdbarch))
return gdbarch_integer_to_address (current_gdbarch, value_type (val),
value_contents (val));
return unpack_long (value_type (val), value_contents (val));
#endif
}
/* Unpack raw data (copied from debugee, target byte order) at VALADDR
as a long, or as a double, assuming the raw data is described
by type TYPE. Knows how to convert different sizes of values
and can convert between fixed and floating point. We don't assume
any alignment for the raw data. Return value is in host byte order.
If you want functions and arrays to be coerced to pointers, and
references to be dereferenced, call value_as_long() instead.
C++: It is assumed that the front-end has taken care of
all matters concerning pointers to members. A pointer
to member which reaches here is considered to be equivalent
to an INT (or some size). After all, it is only an offset. */
LONGEST
unpack_long (struct type *type, const gdb_byte *valaddr)
{
enum type_code code = TYPE_CODE (type);
int len = TYPE_LENGTH (type);
int nosign = TYPE_UNSIGNED (type);
switch (code)
{
case TYPE_CODE_TYPEDEF:
return unpack_long (check_typedef (type), valaddr);
case TYPE_CODE_ENUM:
case TYPE_CODE_FLAGS:
case TYPE_CODE_BOOL:
case TYPE_CODE_INT:
case TYPE_CODE_CHAR:
case TYPE_CODE_RANGE:
case TYPE_CODE_MEMBERPTR:
if (nosign)
return extract_unsigned_integer (valaddr, len);
else
return extract_signed_integer (valaddr, len);
case TYPE_CODE_FLT:
return extract_typed_floating (valaddr, type);
case TYPE_CODE_DECFLOAT:
/* libdecnumber has a function to convert from decimal to integer, but
it doesn't work when the decimal number has a fractional part. */
return decimal_to_doublest (valaddr, len);
case TYPE_CODE_PTR:
case TYPE_CODE_REF:
/* Assume a CORE_ADDR can fit in a LONGEST (for now). Not sure
whether we want this to be true eventually. */
return extract_typed_address (valaddr, type);
default:
error (_("Value can't be converted to integer."));
}
return 0; /* Placate lint. */
}
/* Return a double value from the specified type and address.
INVP points to an int which is set to 0 for valid value,
1 for invalid value (bad float format). In either case,
the returned double is OK to use. Argument is in target
format, result is in host format. */
DOUBLEST
unpack_double (struct type *type, const gdb_byte *valaddr, int *invp)
{
enum type_code code;
int len;
int nosign;
*invp = 0; /* Assume valid. */
CHECK_TYPEDEF (type);
code = TYPE_CODE (type);
len = TYPE_LENGTH (type);
nosign = TYPE_UNSIGNED (type);
if (code == TYPE_CODE_FLT)
{
/* NOTE: cagney/2002-02-19: There was a test here to see if the
floating-point value was valid (using the macro
INVALID_FLOAT). That test/macro have been removed.
It turns out that only the VAX defined this macro and then
only in a non-portable way. Fixing the portability problem
wouldn't help since the VAX floating-point code is also badly
bit-rotten. The target needs to add definitions for the
methods gdbarch_float_format and gdbarch_double_format - these
exactly describe the target floating-point format. The
problem here is that the corresponding floatformat_vax_f and
floatformat_vax_d values these methods should be set to are
also not defined either. Oops!
Hopefully someone will add both the missing floatformat
definitions and the new cases for floatformat_is_valid (). */
if (!floatformat_is_valid (floatformat_from_type (type), valaddr))
{
*invp = 1;
return 0.0;
}
return extract_typed_floating (valaddr, type);
}
else if (code == TYPE_CODE_DECFLOAT)
return decimal_to_doublest (valaddr, len);
else if (nosign)
{
/* Unsigned -- be sure we compensate for signed LONGEST. */
return (ULONGEST) unpack_long (type, valaddr);
}
else
{
/* Signed -- we are OK with unpack_long. */
return unpack_long (type, valaddr);
}
}
/* Unpack raw data (copied from debugee, target byte order) at VALADDR
as a CORE_ADDR, assuming the raw data is described by type TYPE.
We don't assume any alignment for the raw data. Return value is in
host byte order.
If you want functions and arrays to be coerced to pointers, and
references to be dereferenced, call value_as_address() instead.
C++: It is assumed that the front-end has taken care of
all matters concerning pointers to members. A pointer
to member which reaches here is considered to be equivalent
to an INT (or some size). After all, it is only an offset. */
CORE_ADDR
unpack_pointer (struct type *type, const gdb_byte *valaddr)
{
/* Assume a CORE_ADDR can fit in a LONGEST (for now). Not sure
whether we want this to be true eventually. */
return unpack_long (type, valaddr);
}
/* Get the value of the FIELDN'th field (which must be static) of
TYPE. Return NULL if the field doesn't exist or has been
optimized out. */
struct value *
value_static_field (struct type *type, int fieldno)
{
struct value *retval;
if (TYPE_FIELD_STATIC_HAS_ADDR (type, fieldno))
{
retval = value_at (TYPE_FIELD_TYPE (type, fieldno),
TYPE_FIELD_STATIC_PHYSADDR (type, fieldno));
}
else
{
char *phys_name = TYPE_FIELD_STATIC_PHYSNAME (type, fieldno);
struct symbol *sym = lookup_symbol (phys_name, 0, VAR_DOMAIN, 0);
if (sym == NULL)
{
/* With some compilers, e.g. HP aCC, static data members are reported
as non-debuggable symbols */
struct minimal_symbol *msym = lookup_minimal_symbol (phys_name, NULL, NULL);
if (!msym)
return NULL;
else
{
retval = value_at (TYPE_FIELD_TYPE (type, fieldno),
SYMBOL_VALUE_ADDRESS (msym));
}
}
else
{
/* SYM should never have a SYMBOL_CLASS which will require
read_var_value to use the FRAME parameter. */
if (symbol_read_needs_frame (sym))
warning (_("static field's value depends on the current "
"frame - bad debug info?"));
retval = read_var_value (sym, NULL);
}
if (retval && VALUE_LVAL (retval) == lval_memory)
SET_FIELD_PHYSADDR (TYPE_FIELD (type, fieldno),
VALUE_ADDRESS (retval));
}
return retval;
}
/* Change the enclosing type of a value object VAL to NEW_ENCL_TYPE.
You have to be careful here, since the size of the data area for the value
is set by the length of the enclosing type. So if NEW_ENCL_TYPE is bigger
than the old enclosing type, you have to allocate more space for the data.
The return value is a pointer to the new version of this value structure. */
struct value *
value_change_enclosing_type (struct value *val, struct type *new_encl_type)
{
if (TYPE_LENGTH (new_encl_type) <= TYPE_LENGTH (value_enclosing_type (val)))
{
val->enclosing_type = new_encl_type;
return val;
}
else
{
struct value *new_val;
struct value *prev;
new_val = (struct value *) xrealloc (val, sizeof (struct value) + TYPE_LENGTH (new_encl_type));
new_val->enclosing_type = new_encl_type;
/* We have to make sure this ends up in the same place in the value
chain as the original copy, so it's clean-up behavior is the same.
If the value has been released, this is a waste of time, but there
is no way to tell that in advance, so... */
if (val != all_values)
{
for (prev = all_values; prev != NULL; prev = prev->next)
{
if (prev->next == val)
{
prev->next = new_val;
break;
}
}
}
return new_val;
}
}
/* Given a value ARG1 (offset by OFFSET bytes)
of a struct or union type ARG_TYPE,
extract and return the value of one of its (non-static) fields.
FIELDNO says which field. */
struct value *
value_primitive_field (struct value *arg1, int offset,
int fieldno, struct type *arg_type)
{
struct value *v;
struct type *type;
CHECK_TYPEDEF (arg_type);
type = TYPE_FIELD_TYPE (arg_type, fieldno);
/* Handle packed fields */
if (TYPE_FIELD_BITSIZE (arg_type, fieldno))
{
v = value_from_longest (type,
unpack_field_as_long (arg_type,
value_contents (arg1)
+ offset,
fieldno));
v->bitpos = TYPE_FIELD_BITPOS (arg_type, fieldno) % 8;
v->bitsize = TYPE_FIELD_BITSIZE (arg_type, fieldno);
v->offset = value_offset (arg1) + offset
+ TYPE_FIELD_BITPOS (arg_type, fieldno) / 8;
}
else if (fieldno < TYPE_N_BASECLASSES (arg_type))
{
/* This field is actually a base subobject, so preserve the
entire object's contents for later references to virtual
bases, etc. */
v = allocate_value (value_enclosing_type (arg1));
v->type = type;
/* Lazy register values with offsets are not supported. */
if (VALUE_LVAL (arg1) == lval_register && value_lazy (arg1))
value_fetch_lazy (arg1);
if (value_lazy (arg1))
set_value_lazy (v, 1);
else
memcpy (value_contents_all_raw (v), value_contents_all_raw (arg1),
TYPE_LENGTH (value_enclosing_type (arg1)));
v->offset = value_offset (arg1);
v->embedded_offset = (offset + value_embedded_offset (arg1)
+ TYPE_FIELD_BITPOS (arg_type, fieldno) / 8);
}
else
{
/* Plain old data member */
offset += TYPE_FIELD_BITPOS (arg_type, fieldno) / 8;
v = allocate_value (type);
/* Lazy register values with offsets are not supported. */
if (VALUE_LVAL (arg1) == lval_register && value_lazy (arg1))
value_fetch_lazy (arg1);
if (value_lazy (arg1))
set_value_lazy (v, 1);
else
memcpy (value_contents_raw (v),
value_contents_raw (arg1) + offset,
TYPE_LENGTH (type));
v->offset = (value_offset (arg1) + offset
+ value_embedded_offset (arg1));
}
VALUE_LVAL (v) = VALUE_LVAL (arg1);
if (VALUE_LVAL (arg1) == lval_internalvar)
VALUE_LVAL (v) = lval_internalvar_component;
v->location = arg1->location;
VALUE_REGNUM (v) = VALUE_REGNUM (arg1);
VALUE_FRAME_ID (v) = VALUE_FRAME_ID (arg1);
return v;
}
/* Given a value ARG1 of a struct or union type,
extract and return the value of one of its (non-static) fields.
FIELDNO says which field. */
struct value *
value_field (struct value *arg1, int fieldno)
{
return value_primitive_field (arg1, 0, fieldno, value_type (arg1));
}
/* Return a non-virtual function as a value.
F is the list of member functions which contains the desired method.
J is an index into F which provides the desired method.
We only use the symbol for its address, so be happy with either a
full symbol or a minimal symbol.
*/
struct value *
value_fn_field (struct value **arg1p, struct fn_field *f, int j, struct type *type,
int offset)
{
struct value *v;
struct type *ftype = TYPE_FN_FIELD_TYPE (f, j);
char *physname = TYPE_FN_FIELD_PHYSNAME (f, j);
struct symbol *sym;
struct minimal_symbol *msym;
sym = lookup_symbol (physname, 0, VAR_DOMAIN, 0);
if (sym != NULL)
{
msym = NULL;
}
else
{
gdb_assert (sym == NULL);
msym = lookup_minimal_symbol (physname, NULL, NULL);
if (msym == NULL)
return NULL;
}
v = allocate_value (ftype);
if (sym)
{
VALUE_ADDRESS (v) = BLOCK_START (SYMBOL_BLOCK_VALUE (sym));
}
else
{
/* The minimal symbol might point to a function descriptor;
resolve it to the actual code address instead. */
struct objfile *objfile = msymbol_objfile (msym);
struct gdbarch *gdbarch = get_objfile_arch (objfile);
VALUE_ADDRESS (v)
= gdbarch_convert_from_func_ptr_addr
(gdbarch, SYMBOL_VALUE_ADDRESS (msym), &current_target);
}
if (arg1p)
{
if (type != value_type (*arg1p))
*arg1p = value_ind (value_cast (lookup_pointer_type (type),
value_addr (*arg1p)));
/* Move the `this' pointer according to the offset.
VALUE_OFFSET (*arg1p) += offset;
*/
}
return v;
}
/* Unpack a field FIELDNO of the specified TYPE, from the anonymous object at
VALADDR.
Extracting bits depends on endianness of the machine. Compute the
number of least significant bits to discard. For big endian machines,
we compute the total number of bits in the anonymous object, subtract
off the bit count from the MSB of the object to the MSB of the
bitfield, then the size of the bitfield, which leaves the LSB discard
count. For little endian machines, the discard count is simply the
number of bits from the LSB of the anonymous object to the LSB of the
bitfield.
If the field is signed, we also do sign extension. */
LONGEST
unpack_field_as_long (struct type *type, const gdb_byte *valaddr, int fieldno)
{
ULONGEST val;
ULONGEST valmask;
int bitpos = TYPE_FIELD_BITPOS (type, fieldno);
int bitsize = TYPE_FIELD_BITSIZE (type, fieldno);
int lsbcount;
struct type *field_type;
val = extract_unsigned_integer (valaddr + bitpos / 8, sizeof (val));
field_type = TYPE_FIELD_TYPE (type, fieldno);
CHECK_TYPEDEF (field_type);
/* Extract bits. See comment above. */
if (gdbarch_bits_big_endian (current_gdbarch))
lsbcount = (sizeof val * 8 - bitpos % 8 - bitsize);
else
lsbcount = (bitpos % 8);
val >>= lsbcount;
/* If the field does not entirely fill a LONGEST, then zero the sign bits.
If the field is signed, and is negative, then sign extend. */
if ((bitsize > 0) && (bitsize < 8 * (int) sizeof (val)))
{
valmask = (((ULONGEST) 1) << bitsize) - 1;
val &= valmask;
if (!TYPE_UNSIGNED (field_type))
{
if (val & (valmask ^ (valmask >> 1)))
{
val |= ~valmask;
}
}
}
return (val);
}
/* Modify the value of a bitfield. ADDR points to a block of memory in
target byte order; the bitfield starts in the byte pointed to. FIELDVAL
is the desired value of the field, in host byte order. BITPOS and BITSIZE
indicate which bits (in target bit order) comprise the bitfield.
Requires 0 < BITSIZE <= lbits, 0 <= BITPOS+BITSIZE <= lbits, and
0 <= BITPOS, where lbits is the size of a LONGEST in bits. */
void
modify_field (gdb_byte *addr, LONGEST fieldval, int bitpos, int bitsize)
{
ULONGEST oword;
ULONGEST mask = (ULONGEST) -1 >> (8 * sizeof (ULONGEST) - bitsize);
/* If a negative fieldval fits in the field in question, chop
off the sign extension bits. */
if ((~fieldval & ~(mask >> 1)) == 0)
fieldval &= mask;
/* Warn if value is too big to fit in the field in question. */
if (0 != (fieldval & ~mask))
{
/* FIXME: would like to include fieldval in the message, but
we don't have a sprintf_longest. */
warning (_("Value does not fit in %d bits."), bitsize);
/* Truncate it, otherwise adjoining fields may be corrupted. */
fieldval &= mask;
}
oword = extract_unsigned_integer (addr, sizeof oword);
/* Shifting for bit field depends on endianness of the target machine. */
if (gdbarch_bits_big_endian (current_gdbarch))
bitpos = sizeof (oword) * 8 - bitpos - bitsize;
oword &= ~(mask << bitpos);
oword |= fieldval << bitpos;
store_unsigned_integer (addr, sizeof oword, oword);
}
/* Pack NUM into BUF using a target format of TYPE. */
void
pack_long (gdb_byte *buf, struct type *type, LONGEST num)
{
int len;
type = check_typedef (type);
len = TYPE_LENGTH (type);
switch (TYPE_CODE (type))
{
case TYPE_CODE_INT:
case TYPE_CODE_CHAR:
case TYPE_CODE_ENUM:
case TYPE_CODE_FLAGS:
case TYPE_CODE_BOOL:
case TYPE_CODE_RANGE:
case TYPE_CODE_MEMBERPTR:
store_signed_integer (buf, len, num);
break;
case TYPE_CODE_REF:
case TYPE_CODE_PTR:
store_typed_address (buf, type, (CORE_ADDR) num);
break;
default:
error (_("Unexpected type (%d) encountered for integer constant."),
TYPE_CODE (type));
}
}
/* Convert C numbers into newly allocated values. */
struct value *
value_from_longest (struct type *type, LONGEST num)
{
struct value *val = allocate_value (type);
pack_long (value_contents_raw (val), type, num);
return val;
}
/* Create a value representing a pointer of type TYPE to the address
ADDR. */
struct value *
value_from_pointer (struct type *type, CORE_ADDR addr)
{
struct value *val = allocate_value (type);
store_typed_address (value_contents_raw (val), type, addr);
return val;
}
/* Create a value for a string constant to be stored locally
(not in the inferior's memory space, but in GDB memory).
This is analogous to value_from_longest, which also does not
use inferior memory. String shall NOT contain embedded nulls. */
struct value *
value_from_string (char *ptr)
{
struct value *val;
int len = strlen (ptr);
int lowbound = current_language->string_lower_bound;
struct type *string_char_type;
struct type *rangetype;
struct type *stringtype;
rangetype = create_range_type ((struct type *) NULL,
builtin_type_int,
lowbound, len + lowbound - 1);
string_char_type = language_string_char_type (current_language,
current_gdbarch);
stringtype = create_array_type ((struct type *) NULL,
string_char_type,
rangetype);
val = allocate_value (stringtype);
memcpy (value_contents_raw (val), ptr, len);
return val;
}
struct value *
value_from_double (struct type *type, DOUBLEST num)
{
struct value *val = allocate_value (type);
struct type *base_type = check_typedef (type);
enum type_code code = TYPE_CODE (base_type);
int len = TYPE_LENGTH (base_type);
if (code == TYPE_CODE_FLT)
{
store_typed_floating (value_contents_raw (val), base_type, num);
}
else
error (_("Unexpected type encountered for floating constant."));
return val;
}
struct value *
value_from_decfloat (struct type *type, const gdb_byte *dec)
{
struct value *val = allocate_value (type);
memcpy (value_contents_raw (val), dec, TYPE_LENGTH (type));
return val;
}
struct value *
coerce_ref (struct value *arg)
{
struct type *value_type_arg_tmp = check_typedef (value_type (arg));
if (TYPE_CODE (value_type_arg_tmp) == TYPE_CODE_REF)
arg = value_at_lazy (TYPE_TARGET_TYPE (value_type_arg_tmp),
unpack_pointer (value_type (arg),
value_contents (arg)));
return arg;
}
struct value *
coerce_array (struct value *arg)
{
arg = coerce_ref (arg);
if (current_language->c_style_arrays
&& TYPE_CODE (value_type (arg)) == TYPE_CODE_ARRAY)
arg = value_coerce_array (arg);
if (TYPE_CODE (value_type (arg)) == TYPE_CODE_FUNC)
arg = value_coerce_function (arg);
return arg;
}
struct value *
coerce_number (struct value *arg)
{
arg = coerce_array (arg);
arg = coerce_enum (arg);
return arg;
}
struct value *
coerce_enum (struct value *arg)
{
if (TYPE_CODE (check_typedef (value_type (arg))) == TYPE_CODE_ENUM)
arg = value_cast (builtin_type_unsigned_int, arg);
return arg;
}
/* Return true if the function returning the specified type is using
the convention of returning structures in memory (passing in the
address as a hidden first parameter). */
int
using_struct_return (struct type *func_type, struct type *value_type)
{
enum type_code code = TYPE_CODE (value_type);
if (code == TYPE_CODE_ERROR)
error (_("Function return type unknown."));
if (code == TYPE_CODE_VOID)
/* A void return value is never in memory. See also corresponding
code in "print_return_value". */
return 0;
/* Probe the architecture for the return-value convention. */
return (gdbarch_return_value (current_gdbarch, func_type, value_type,
NULL, NULL, NULL)
!= RETURN_VALUE_REGISTER_CONVENTION);
}
/* Set the initialized field in a value struct. */
void
set_value_initialized (struct value *val, int status)
{
val->initialized = status;
}
/* Return the initialized field in a value struct. */
int
value_initialized (struct value *val)
{
return val->initialized;
}
void
_initialize_values (void)
{
add_cmd ("convenience", no_class, show_convenience, _("\
Debugger convenience (\"$foo\") variables.\n\
These variables are created when you assign them values;\n\
thus, \"print $foo=1\" gives \"$foo\" the value 1. Values may be any type.\n\
\n\
A few convenience variables are given values automatically:\n\
\"$_\"holds the last address examined with \"x\" or \"info lines\",\n\
\"$__\" holds the contents of the last address examined with \"x\"."),
&showlist);
add_cmd ("values", no_class, show_values,
_("Elements of value history around item number IDX (or last ten)."),
&showlist);
add_com ("init-if-undefined", class_vars, init_if_undefined_command, _("\
Initialize a convenience variable if necessary.\n\
init-if-undefined VARIABLE = EXPRESSION\n\
Set an internal VARIABLE to the result of the EXPRESSION if it does not\n\
exist or does not contain a value. The EXPRESSION is not evaluated if the\n\
VARIABLE is already initialized."));
}