RFA: addresses and pointers may be different sizes while printing

[Jim Blandy <jimb at zwingli dot cygnus dot com>]

Hi, David.  I think printcmd.c is "language support", so I need your
approval/criticism for the below patch.  There are examples and more
explanation in this thread on gdb-patches.

------- Start of forwarded message -------
From: Jim Blandy <jimb@cygnus.com>
To: gdb-patches@sources.redhat.com
Subject: RFA: addresses and pointers may be different sizes while printing
Message-Id: <20010628223546.BDE7F5E9CB@zwingli.cygnus.com>
Date: Thu, 28 Jun 2001 17:35:46 -0500 (EST)


This is a preparatory patch for removing the D10V dependencies that
have crept into the core of GDB (for example: value_at in valops.c).

The D10V uses 16-bit pointers to index 256k code space.  Since all
D10V instructions are 32 bits long, and naturally aligned, the PC is
really 18 bits long, and the bottom two bits are always zero.  Within
GDB, we model this by using 32-bit *addresses*, and converting
*pointers* (which are 16 bits long) to *addresses* at the appropriate
points.

Without this conversion (which is necessary for some other
architectures as well), the alternative is for GDB to think that
pointers are 32 bits long, while the program being debugged thinks
they're 16 bits long.  As you'd expect, chaos results.

In any case, print_scalar_formatted assumes that pointers and the
addresses they represent are the same length.  This isn't true for the
D10V, so we need to remove that assumption.  That's what this patch is
supposed to do.

There are probably similar problems elsewhere, but we can fix them as
we find them.  I found this one, so I'm fixing it.

2001-06-28  Jim Blandy  <jimb@redhat.com>

	* printcmd.c (print_scalar_formatted): If we are printing an
	address, remember that TARGET_ADDR_BIT is not always equal to
	TARGET_PTR_BIT.

Index: gdb/printcmd.c
===================================================================
RCS file: /cvs/src/src/gdb/printcmd.c,v
retrieving revision 1.21
diff -c -r1.21 printcmd.c
*** gdb/printcmd.c	2001/06/11 16:05:24	1.21
--- gdb/printcmd.c	2001/06/28 22:25:00
***************
*** 390,395 ****
--- 390,401 ----
    else if (format != 'f')
      val_long = unpack_long (type, valaddr);
  
+   /* If the value is a pointer, and pointers and addresses are not the
+      same, then at this point, the value's length is TARGET_ADDR_BIT, not
+      TYPE_LENGTH (type).  */
+   if (TYPE_CODE (type) == TYPE_CODE_PTR)
+     len = TARGET_ADDR_BIT;
+ 
    /* If we are printing it as unsigned, truncate it in case it is actually
       a negative signed value (e.g. "print/u (short)-1" should print 65535
       (if shorts are 16 bits) instead of 4294967295).  */
 

------- End of forwarded message -------