[rfc] Re-parse display expressions if architecture changes

[Ulrich Weigand]

Tom Tromey wrote:
> >>>>> "Ulrich" == Ulrich Weigand <uweigand@de.ibm.com> writes:
> 
> Ulrich> The patch below implements this by ensuring the expression is
> Ulrich> re-parsed if the currnet architecture is different from the one
> Ulrich> the expression was originally parsed in.
> 
> This seems like a reasonable idea to me.
> 
> Ulrich> Any comments?  I'm planning to apply this next week.
> 
> I think this needs to xfree the old expression to avoid a memory leak.

Oops, thanks for noticing this.  Updated patch below.

Bye,
Ulrich


ChangeLog:

	* printcmd.c: Include "arch-utils.h".
	(do_one_display): Re-parse expression if current architecture changed.


diff -urNp gdb-orig/gdb/printcmd.c gdb-head/gdb/printcmd.c
--- gdb-orig/gdb/printcmd.c	2009-12-18 17:27:13.000000000 +0100
+++ gdb-head/gdb/printcmd.c	2009-12-22 14:23:27.000000000 +0100
@@ -49,6 +49,7 @@
 #include "solib.h"
 #include "parser-defs.h"
 #include "charset.h"
+#include "arch-utils.h"
 
 #ifdef TUI
 #include "tui/tui.h"		/* For tui_active et.al.   */
@@ -1597,6 +1598,20 @@ do_one_display (struct display *d)
   if (d->enabled_p == 0)
     return;
 
+  /* The expression carries the architecture that was used at parse time.
+     This is a problem if the expression depends on architecture features
+     (e.g. register numbers), and the current architecture is now different.
+     For example, a display statement like "display/i $pc" is expected to
+     display the PC register of the current architecture, not the arch at
+     the time the display command was given.  Therefore, we re-parse the
+     expression if the current architecture has changed.  */
+  if (d->exp != NULL && d->exp->gdbarch != get_current_arch ())
+    {
+      xfree (d->exp);
+      d->exp = NULL;
+      d->block = NULL;
+    }
+
   if (d->exp == NULL)
     {
       volatile struct gdb_exception ex;

-- 
  Dr. Ulrich Weigand
  GNU Toolchain for Linux on System z and Cell BE
  Ulrich.Weigand@de.ibm.com