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Re: RFA: handle zero-length types in value_from_register
Andrew Cagney <cagney@gnu.org> writes:
> > Andrew Cagney <cagney@gnu.org> writes:
> >
> >> > 2004-01-27 Jim Blandy <jimb@redhat.com>
> >> > * findvar.c (value_from_register): If the type has no length,
> >> > just
> >> > return an acceptable value --- don't report an internal error.
> >> >
> >
> >> This looks to need a test case.
> > I tried to put one together, but the bug only occurs when the
> > zero-length value is allocated to a register. I couldn't find any way
> > to make that happen at all. So the only known instance of this bug
> > depends on bad debug info.
>
> The commentary should really reflect this important detail (also
> mention the compiler that's broken for instance). Should GDB also
> complain about the bogus info?
Seems reasonable. I've attached a revision of the original patch,
with an expanded comment, and a separate patch that makes GDB complain
when it sees the bogus info.
2004-01-27 Jim Blandy <jimb@redhat.com>
* findvar.c (value_from_register): If the type has no length, just
return an acceptable value --- don't report an internal error.
Index: gdb/findvar.c
===================================================================
RCS file: /cvs/src/src/gdb/findvar.c,v
retrieving revision 1.68
diff -c -r1.68 findvar.c
*** gdb/findvar.c 26 Jan 2004 20:36:32 -0000 1.68
--- gdb/findvar.c 28 Jan 2004 05:47:05 -0000
***************
*** 617,623 ****
struct value *v = allocate_value (type);
CHECK_TYPEDEF (type);
! if (CONVERT_REGISTER_P (regnum, type))
{
/* The ISA/ABI need to something weird when obtaining the
specified value from this register. It might need to
--- 617,646 ----
struct value *v = allocate_value (type);
CHECK_TYPEDEF (type);
! if (TYPE_LENGTH (type) == 0)
! {
! /* It doesn't matter much what we return for this: since the
! length is zero, it could be anything. But if allowed to see
! a zero-length type, the register-finding loop below will set
! neither mem_stor nor reg_stor, and then report an internal
! error.
!
! Zero-length types can legitimately arise from declarations
! like 'struct {}'. GDB may also create them when it finds
! bogus debugging information; for example, in GCC 2.94.4 and
! binutils 2.11.93.0.2, the STABS BINCL->EXCL compression
! process can create bad type numbers. GDB reads these as
! TYPE_CODE_UNDEF types, with zero length. (That bug is
! actually the only known way to get a zero-length value
! allocated to a register --- which is what it takes to make it
! here.)
!
! We'll just attribute the value to the original register. */
! VALUE_LVAL (v) = lval_register;
! VALUE_ADDRESS (v) = regnum;
! VALUE_REGNO (v) = regnum;
! }
! else if (CONVERT_REGISTER_P (regnum, type))
{
/* The ISA/ABI need to something weird when obtaining the
specified value from this register. It might need to
2004-01-27 Jim Blandy <jimb@redhat.com>
* stabsread.c (read_type): If we find any type numbers that are
forward references, complain if the references aren't resolved by
the time we're finished reading.
(cleanup_undefined_types): Make error message more appropriate for
a complaint.
Index: gdb/stabsread.c
===================================================================
RCS file: /cvs/src/src/gdb/stabsread.c,v
retrieving revision 1.72
diff -c -r1.72 stabsread.c
*** gdb/stabsread.c 19 Jan 2004 01:20:11 -0000 1.72
--- gdb/stabsread.c 28 Jan 2004 05:39:16 -0000
***************
*** 1446,1456 ****
if (read_type_number (pp, typenums) != 0)
return error_type (pp, objfile);
- /* Type is not being defined here. Either it already exists,
- or this is a forward reference to it. dbx_alloc_type handles
- both cases. */
if (**pp != '=')
! return dbx_alloc_type (typenums, objfile);
/* Type is being defined here. */
/* Skip the '='.
--- 1446,1466 ----
if (read_type_number (pp, typenums) != 0)
return error_type (pp, objfile);
if (**pp != '=')
! {
! /* Type is not being defined here. Either it already
! exists, or this is a forward reference to it.
! dbx_alloc_type handles both cases. */
! type = dbx_alloc_type (typenums, objfile);
!
! /* If this is a forward reference, arrange to complain if it
! doesn't get patched up by the time we're done
! reading. */
! if (TYPE_CODE (type) == TYPE_CODE_UNDEF)
! add_undefined_type (type);
!
! return type;
! }
/* Type is being defined here. */
/* Skip the '='.
***************
*** 4197,4203 ****
default:
{
complaint (&symfile_complaints,
! "GDB internal error. cleanup_undefined_types with bad type %d.",
TYPE_CODE (*type));
}
break;
--- 4207,4214 ----
default:
{
complaint (&symfile_complaints,
! "forward-referenced types left unresolved, "
! "type code %d.",
TYPE_CODE (*type));
}
break;