[RFC] Use target vector inheritance for GNU/Linux

[Andrew Cagney]

> -LONGEST 
> -ia64_linux_xfer_unwind_table (struct target_ops *ops,
> -			      enum target_object object,
> -			      const char *annex,
> -			      void *readbuf, const void *writebuf,
> -			      ULONGEST offset, LONGEST len)
> +LONGEST (*saved_xfer_partial) (struct target_ops *, enum target_object,
> +			       const char *, void *, const void *,
> +			       ULONGEST, LONGEST);
> +
> +static LONGEST 
> +ia64_linux_xfer_partial (struct target_ops *ops,
> +			 enum target_object object,
> +			 const char *annex,
> +			 void *readbuf, const void *writebuf,
> +			 ULONGEST offset, LONGEST len)
>  {
> -  return syscall (__NR_getunwind, readbuf, len);
> +  if (object == TARGET_OBJECT_UNWIND_TABLE && writebuf == NULL && offset == 0)
> +    return syscall (__NR_getunwind, readbuf, len);
> +
> +  return saved_xfer_partial (ops, object, annex, readbuf, writebuf,
> +			     offset, len);
> +}

Can you rename saved_xfer_partial to super_xfer_partial_hack and add a 
FIXME.  It should be calling super.xfer_partial but that's not available :-(

+#ifndef FETCH_INFERIOR_REGISTERS
+
+/* Fetch register REGNUM from the inferior.  */
+
+static void
+fetch_register (int regnum)
+{

Why is this wrapped in in an #ifdef?

+/* Create a generic GNU/Linux target vector.  If T is non-NULL, base
+   the new target vector on it.  */
+
+struct target_ops *
+linux_target (struct target_ops *t)

Can this be renamed to inf_linux_target (to be consistent with the other 
inf_*_target() methods?

> A new function, linux_target, is added to linux-nat.c.  Then any GNU/Linux
> target can call it, and pass the result to add_target - after specializing
> whatever methods it needs to.  Sometimes it's necessary to specialize a
> method between inf_ptrace_target and linux_target, so it accepts an optional
> argument.  This wouldn't be necessary if all target methods took a
> target_ops parameter, so they could call the overridden method.

As in this?

> +void
> +_initialize_i386_linux_nat (void)
> +{
> +  struct target_ops *t = inf_ptrace_target ();
> +
> +  /* Override the default ptrace resume method.  */
> +  t->to_resume = i386_linux_resume;
> +
> +  /* Fill in the generic GNU/Linux methods.  */
> +  t = linux_target (t);

which is violating the inheritance structure.  Can you instead add a 
one-of method (deprecated_set_super_linux_resume?) to handle this case? 
  We can then see about fixing the problem (I'm left wondering if that 
method is still needed).

> +  /* FIXME drow/2004-12-04: For now, these functions must keep the standard
> +     names because only some GNU/Linux targets use inf-ptrace.o.  When all
> +     have been converted, these functions can be renamed and made static.  */

Is this still true?  I thought the patch was so large because it touched 
all the linux targets.

Andrew