Re: printing "variable-sized" registers

[Vladimir Prus <ghost at cs dot msu dot su>]

On Monday 30 May 2005 20:58, Daniel Jacobowitz wrote:
> On Mon, May 30, 2005 at 06:22:19PM +0400, Vladimir Prus wrote:
> > Hello,
> > I'm working on a gdb port, and have problems with printing certain
> > registers of my target. The problem is that those registers are vector
> > buffers that can hold from 0 to 32 values at any given moment. I would
> > like the 'info registers' command to print exactly the number of values
> > that are present in a buffer. That is, on one invocation I might get 4
> > values printed, and on another 15, depending on the current processor
> > state.
> >
> > However, I don't see an easy way to do this. The
> > 'default_print_registers_info' function uses 'val_print' to print the
> > value, and 'val_print' uses register type (struct type*), which has a
> > fixed size. Anything I can do? Or I should just write arch-specific
> > 'print_registers_info' function?
>
> The last one.  The best you can do the rest of the time is going to be
> giving them a type containing the maximum number of values and fill in
> with dummies - maybe also including the count?

This's what I was doing -- assigning "array of 32 uin64s" type to those 
registers and they are printed with "info all-registers", but the dummy
values do no look nice when presented to the user.

> If you want "print $reg" to display them nicely, you're going to need
> to teach GDB's type system about it somehow.  I have no idea what that
> change would look like or how it would work, but it could be generally
> useful - it's the same concept as prettyprinting a tagged union, I think.

Ok, understood. With the attached patch I get what I want, but I have no idea 
if this patch is good or not.

- Volodya



diff -u gdb-6.3-orig/gdb/gdbtypes.h gdb-6.3/gdb/gdbtypes.h
--- gdb-6.3-orig/gdb/gdbtypes.h	2004-10-01 14:23:09.000000000 +0400
+++ gdb-6.3/gdb/gdbtypes.h	2005-05-31 10:19:42.000000000 +0400
@@ -304,6 +304,12 @@
 
 #define TYPE_FLAG_FIXED_INSTANCE (1 << 15)
 
+
+#define  TYPE_FLAG_VARIABLE_SIZED_ARRAY (1 << 16)
+#define  TYPE_VARIABLE_SIZED_ARRAY(t) (TYPE_INSTANCE_FLAGS(t) \
+                                       & TYPE_FLAG_VARIABLE_SIZED_ARRAY)
+
+
 /*  Array bound type.  */
 enum array_bound_type
 {

diff -u gdb-6.3-orig/gdb/valprint.c gdb-6.3/gdb/valprint.c
--- gdb-6.3-orig/gdb/valprint.c	2004-09-12 20:13:04.000000000 +0400
+++ gdb-6.3/gdb/valprint.c	2005-05-31 11:23:09.000000000 +0400
@@ -774,10 +774,15 @@
 
   elttype = TYPE_TARGET_TYPE (type);
   eltlen = TYPE_LENGTH (check_typedef (elttype));
-  len = TYPE_LENGTH (type) / eltlen;
 
   annotate_array_section_begin (i, elttype);
 
+  if (TYPE_VARIABLE_SIZED_ARRAY(type)) {
+      len = *(unsigned int*)valaddr;
+      valaddr += sizeof(unsigned int);
+  } else
+      len = TYPE_LENGTH (type) / eltlen;
+
   for (; i < len && things_printed < print_max; i++)
     {
       if (i != 0)