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always read synthetic pointers as signed integers

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I see the error message "access outside bounds of object referenced
via synthetic pointer" in the two fails below of mips gdb testing

print d[-2]^M
access outside bounds of object referenced via synthetic pointer^M
(gdb) FAIL: gdb.dwarf2/implptrconst.exp: print d[-2]
(gdb) print/d p[-1]^M
access outside bounds of object referenced via synthetic pointer^M
(gdb) FAIL: gdb.dwarf2/implptrpiece.exp: print/d p[-1]

in the first test, 'd[-2]' is processed by GDB as '* (&d[-2])'.  'd'
is a synthetic pointer, so its value is zero, the address of 'd[-2]'
is -2.  In dwarf2loc.c:indirect_pieced_value,

  /* This is an offset requested by GDB, such as value subscripts.
     However, due to how synthetic pointers are implemented, this is
     always presented to us as a pointer type.  This means we have to
     sign-extend it manually as appropriate.  */
  byte_offset = value_as_address (value);
  if (TYPE_LENGTH (value_type (value)) < sizeof (LONGEST))
    byte_offset = gdb_sign_extend (byte_offset,
				   8 * TYPE_LENGTH (value_type (value)));
  byte_offset += piece->v.ptr.offset;

We know that the value is really an offset instead of address, so the
fix is to extract the value as an (signed) offset.

gdb:

2015-01-08  Pedro Alves  <palves@redhat.com>
	    Yao Qi  <yao@codesourcery.com>

	* dwarf2loc.c (indirect_pieced_value): Don't call
	gdb_sign_extend.  Call extract_signed_integer instead.
	* utils.c (gdb_sign_extend): Remove.
	* utils.h (gdb_sign_extend): Remove declaration.
This commit is contained in:
Yao Qi 2014-12-28 16:12:53 +08:00
parent 3565cf8fed
commit b597c318b8
4 changed files with 19 additions and 27 deletions
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8
gdb/ChangeLog
View file

@ -1,3 +1,11 @@
2015-01-08 Pedro Alves <palves@redhat.com>
Yao Qi <yao@codesourcery.com>
* dwarf2loc.c (indirect_pieced_value): Don't call
gdb_sign_extend. Call extract_signed_integer instead.
* utils.c (gdb_sign_extend): Remove.
* utils.h (gdb_sign_extend): Remove declaration.
2015-01-07 Pierre Muller <muller@sourceware.org>
PR symtab/17811

16
gdb/dwarf2loc.c
View file

@ -2012,6 +2012,7 @@ indirect_pieced_value (struct value *value)
int i, bit_offset, bit_length;
struct dwarf_expr_piece *piece = NULL;
LONGEST byte_offset;
enum bfd_endian byte_order;
type = check_typedef (value_type (value));
if (TYPE_CODE (type) != TYPE_CODE_PTR)
@ -2056,11 +2057,16 @@ indirect_pieced_value (struct value *value)
/* This is an offset requested by GDB, such as value subscripts.
However, due to how synthetic pointers are implemented, this is
always presented to us as a pointer type. This means we have to
sign-extend it manually as appropriate. */
byte_offset = value_as_address (value);
if (TYPE_LENGTH (value_type (value)) < sizeof (LONGEST))
byte_offset = gdb_sign_extend (byte_offset,
8 * TYPE_LENGTH (value_type (value)));
sign-extend it manually as appropriate. Use raw
extract_signed_integer directly rather than value_as_address and
sign extend afterwards on architectures that would need it
(mostly everywhere except MIPS, which has signed addresses) as
the later would go through gdbarch_pointer_to_address and thus
return a CORE_ADDR with high bits set on architectures that
encode address spaces and other things in CORE_ADDR. */
byte_order = gdbarch_byte_order (get_frame_arch (frame));
byte_offset = extract_signed_integer (value_contents (value),
TYPE_LENGTH (type), byte_order);
byte_offset += piece->v.ptr.offset;
gdb_assert (piece);

17
gdb/utils.c
View file

@ -3021,23 +3021,6 @@ align_down (ULONGEST v, int n)
return (v & -n);
}
/* See utils.h. */
LONGEST
gdb_sign_extend (LONGEST value, int bit)
{
gdb_assert (bit >= 1 && bit <= 8 * sizeof (LONGEST));
if (((value >> (bit - 1)) & 1) != 0)
{
LONGEST signbit = ((LONGEST) 1) << (bit - 1);
value = (value ^ signbit) - signbit;
}
return value;
}
/* Allocation function for the libiberty hash table which uses an
obstack. The obstack is passed as DATA. */

5
gdb/utils.h
View file

@ -340,11 +340,6 @@ extern int myread (int, char *, int);
extern ULONGEST align_up (ULONGEST v, int n);
extern ULONGEST align_down (ULONGEST v, int n);
/* Sign extend VALUE. BIT is the (1-based) index of the bit in VALUE
to sign-extend. */
extern LONGEST gdb_sign_extend (LONGEST value, int bit);
/* Resource limits used by getrlimit and setrlimit. */
enum resource_limit_kind