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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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5
gdb/utils.h
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@ -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