[rfc] Some changes to the examine ("x") command

["Ulrich Weigand" <uweigand at de dot ibm dot com>]

Hello,

this patch makes a number of changes to the examine ("x") command
implementation to remove reference to global types and current_gdbarch.

In particular, this includes the following:

- No longer use the examine_..._type global type variables, but the
  generic builtin_type_int... types to represent the values examined
  by the "x" command.  (These can then later be replaced by per-
  architecture versions of those types.)

- Do not attempt to determine the target address size in decode_format.
  Instead, encode the request for address size as a special value 'a'
  of the "size" format code, and act upon that in do_examine, where we
  actually know the architecture to which the command applies.

- In addition to the global "next_address", use a global "next_gdbarch"
  variable to track the architecture associated with that address.  Use
  this architecture in do_examine to determine target properties like
  address size (and in the future, per-architecture types).

There is one instance where next_address is, and thus next_gdbarch would be,
used un-initialized: When an "x" command with no address argument is used,
and no other command that sets the "next" display address was ever used
before in the GDB session.

In that situation, GDB currently uses the default 0 value of next_address
and starts displaying data at address 0 (which on most targets would fail
anyway).  With the new next_gdbarch we have the problem that we do not even
have such a default.  (We could fall back to the current frame architecture
or something like that, but this doesn't seem to be very useful to me.)

The patch below treats this case as a user error and returns an error
stating that an intial display address needs to be specified.  (I've
also had to adapt a test cast to accept the new behaviour.)

Tested on amd64-linux and powerpc64-linux.

Bye,
Ulrich


ChangeLog:

	* printcmd.c (next_gdbarch): New static variable.
	(set_next_address, do_examine, x_command): Set it.
	(decode_format): Use 'a' size to indicate width of an address.
	(do_examine): Add GDBARCH argument.  Handle 'a' size.
	(x_command): Pass architecture to do_examine.
	Error if called without argument the first time.  
	(do_one_display): Pass architecture to do_examine.

	(examine_i_type, examine_b_type, examine_h_type, examine_w_type,
	examine_g_type): Remove.
	(_initialize_printcmd): Do not initialize them.
	(do_examine): Use builin_type_int... instead of examine_..._type.

	* testsuite/gdb.base/default.exp: Update test case.


Index: gdb-head/gdb/printcmd.c
===================================================================
--- gdb-head.orig/gdb/printcmd.c
+++ gdb-head/gdb/printcmd.c
@@ -82,8 +82,9 @@ static char last_format = 0;
 
 static char last_size = 'w';
 
-/* Default address to examine next.  */
+/* Default address to examine next, and associated architecture.  */
 
+static struct gdbarch *next_gdbarch;
 static CORE_ADDR next_address;
 
 /* Number of delay instructions following current disassembled insn.  */
@@ -231,18 +232,10 @@ decode_format (char **string_ptr, int of
     switch (val.format)
       {
       case 'a':
-      case 's':
-	/* Pick the appropriate size for an address.  */
-	if (gdbarch_ptr_bit (current_gdbarch) == 64)
-	  val.size = osize ? 'g' : osize;
-	else if (gdbarch_ptr_bit (current_gdbarch) == 32)
-	  val.size = osize ? 'w' : osize;
-	else if (gdbarch_ptr_bit (current_gdbarch) == 16)
-	  val.size = osize ? 'h' : osize;
-	else
-	  /* Bad value for gdbarch_ptr_bit.  */
-	  internal_error (__FILE__, __LINE__,
-			  _("failed internal consistency check"));
+	/* Pick the appropriate size for an address.  This is deferred
+	   until do_examine when we know the actual architecture to use.
+	   A special size value of 'a' is used to indicate this case.  */
+	val.size = osize ? 'a' : osize;
 	break;
       case 'f':
 	/* Floating point has to be word or giantword.  */
@@ -540,6 +533,7 @@ set_next_address (struct gdbarch *gdbarc
 {
   struct type *ptr_type = builtin_type (gdbarch)->builtin_data_ptr;
 
+  next_gdbarch = gdbarch;
   next_address = addr;
 
   /* Make address available to the user as $_.  */
@@ -745,21 +739,11 @@ print_address_demangle (CORE_ADDR addr, 
 }
 
 
-/* These are the types that $__ will get after an examine command of one
-   of these sizes.  */
-
-static struct type *examine_i_type;
-
-static struct type *examine_b_type;
-static struct type *examine_h_type;
-static struct type *examine_w_type;
-static struct type *examine_g_type;
-
 /* Examine data at address ADDR in format FMT.
    Fetch it from memory and print on gdb_stdout.  */
 
 static void
-do_examine (struct format_data fmt, CORE_ADDR addr)
+do_examine (struct format_data fmt, struct gdbarch *gdbarch, CORE_ADDR addr)
 {
   char format = 0;
   char size;
@@ -772,6 +756,7 @@ do_examine (struct format_data fmt, CORE
   format = fmt.format;
   size = fmt.size;
   count = fmt.count;
+  next_gdbarch = gdbarch;
   next_address = addr;
 
   /* String or instruction format implies fetch single bytes
@@ -779,16 +764,29 @@ do_examine (struct format_data fmt, CORE
   if (format == 's' || format == 'i')
     size = 'b';
 
-  if (format == 'i')
-    val_type = examine_i_type;
-  else if (size == 'b')
-    val_type = examine_b_type;
+  if (size == 'a')
+    {
+      /* Pick the appropriate size for an address.  */
+      if (gdbarch_ptr_bit (next_gdbarch) == 64)
+	size = 'g';
+      else if (gdbarch_ptr_bit (next_gdbarch) == 32)
+	size = 'w';
+      else if (gdbarch_ptr_bit (next_gdbarch) == 16)
+	size = 'h';
+      else
+	/* Bad value for gdbarch_ptr_bit.  */
+	internal_error (__FILE__, __LINE__,
+			_("failed internal consistency check"));
+    }
+
+  if (size == 'b')
+    val_type = builtin_type_int8;
   else if (size == 'h')
-    val_type = examine_h_type;
+    val_type = builtin_type_int16;
   else if (size == 'w')
-    val_type = examine_w_type;
+    val_type = builtin_type_int32;
   else if (size == 'g')
-    val_type = examine_g_type;
+    val_type = builtin_type_int64;
 
   maxelts = 8;
   if (size == 'w')
@@ -1356,10 +1354,15 @@ x_command (char *exp, int from_tty)
 	next_address = value_address (val);
       else
 	next_address = value_as_address (val);
+
+      next_gdbarch = expr->gdbarch;
       do_cleanups (old_chain);
     }
 
-  do_examine (fmt, next_address);
+  if (!next_gdbarch)
+    error_no_arg (_("starting display address"));
+
+  do_examine (fmt, next_gdbarch, next_address);
 
   /* If the examine succeeds, we remember its size and format for next
      time.  */
@@ -1620,7 +1623,7 @@ do_one_display (struct display *d)
 
       annotate_display_value ();
 
-      do_examine (d->format, addr);
+      do_examine (d->format, d->exp->gdbarch, addr);
     }
   else
     {
@@ -2733,15 +2736,4 @@ Show printing of source filename and lin
 			   NULL,
 			   show_print_symbol_filename,
 			   &setprintlist, &showprintlist);
-
-  /* For examine/instruction a single byte quantity is specified as
-     the data.  This avoids problems with value_at_lazy() requiring a
-     valid data type (and rejecting VOID). */
-  examine_i_type = init_type (TYPE_CODE_INT, 1, 0, "examine_i_type", NULL);
-
-  examine_b_type = init_type (TYPE_CODE_INT, 1, 0, "examine_b_type", NULL);
-  examine_h_type = init_type (TYPE_CODE_INT, 2, 0, "examine_h_type", NULL);
-  examine_w_type = init_type (TYPE_CODE_INT, 4, 0, "examine_w_type", NULL);
-  examine_g_type = init_type (TYPE_CODE_INT, 8, 0, "examine_g_type", NULL);
-
 }
Index: gdb-head/gdb/testsuite/gdb.base/default.exp
===================================================================
--- gdb-head.orig/gdb/testsuite/gdb.base/default.exp
+++ gdb-head/gdb/testsuite/gdb.base/default.exp
@@ -798,17 +798,6 @@ gdb_test "whatis" "The history is empty.
 #test where
 gdb_test "where" "No stack." "where"
 #test x
-#The case in which it prints a number is for vxgdb.
-send_gdb "x\n"
-gdb_expect {
-    -re "0x0:.*Cannot access memory at address 0x0..*$gdb_prompt $" {
-        pass "x"
-    }
-    -re "0x0:.*Error accessing memory address 0x0:.*$gdb_prompt $" {
-        pass "x"
-    }
-    -re ".*$gdb_prompt $" { fail "x" }
-    timeout { fail "(timeout) x" }
-}
+gdb_test "x" "Argument required .starting display address.*" "x"
 
 gdb_exit
-- 
  Dr. Ulrich Weigand
  GNU Toolchain for Linux on System z and Cell BE
  Ulrich.Weigand@de.ibm.com