Re: [PATCH] Fixup internal variables' endian (again)

[Andrew STUBBS <andrew.stubbs@st.com>]

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Daniel Jacobowitz wrote:
> So, if you've got a symbol file and the endianness is set wrong, you
> can do this.  I guess that counts as going out of their way, but it
> doesn't match what you wrote originally, which was that you could never
> produce such internalvars.

Ah well, there's always another, more devious, way to do everything.
But, as you say, once the symbol table is loaded there ought to be no
endian issues unless the user brings it on themselves.

The patch solves the problem where built-in types are set before the
file is loaded, which is what I wanted to fix.

>> I don't actually know of a host/target where
>> this is a problem, but I'm sure there are some out there.
> 
> Where switching endianness affects the floating point format? 
> Everything but ARM FPA, as far as I know.

Well, I've tested it on x86 and sh4, and on both those platforms you can
'set endian ..' as much as you like and the floats are always shown
correctly. On a Sparc the numbers do come through garbled in the wrong
endian.

> Could you put spaces around the equals signs, please.
> 
> OK with that change.

Thanks, committed with that change.

The final patch is attached.

Andrew Stubbs

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2006-03-31  Andrew Stubbs  <andrew.stubbs@st.com>

	* value.h (struct internalvar): Add field 'endian'.
	* value.c (lookup_internalvar): Initialise endian.
	(value_of_internalvar): Flip the endian of built-in types if required.
	(set_internalvar): Set the endian.
	(show_convenience): Access the value through value_of_internalvar().


Index: src/gdb/value.c
===================================================================
--- src.orig/gdb/value.c	2006-02-01 23:14:10.000000000 +0000
+++ src/gdb/value.c	2006-03-31 11:10:21.000000000 +0100
@@ -755,6 +755,7 @@ lookup_internalvar (char *name)
   var = (struct internalvar *) xmalloc (sizeof (struct internalvar));
   var->name = concat (name, (char *)NULL);
   var->value = allocate_value (builtin_type_void);
+  var->endian = TARGET_BYTE_ORDER;
   release_value (var->value);
   var->next = internalvars;
   internalvars = var;
@@ -765,12 +766,46 @@ struct value *
 value_of_internalvar (struct internalvar *var)
 {
   struct value *val;
+  int i, j;
+  gdb_byte temp;
 
   val = value_copy (var->value);
   if (value_lazy (val))
     value_fetch_lazy (val);
   VALUE_LVAL (val) = lval_internalvar;
   VALUE_INTERNALVAR (val) = var;
+
+  /* Values are always stored in the target's byte order.  When connected to a
+     target this will most likely always be correct, so there's normally no
+     need to worry about it.
+
+     However, internal variables can be set up before the target endian is
+     known and so may become out of date.  Fix it up before anybody sees.
+
+     Internal variables usually hold simple scalar values, and we can
+     correct those.  More complex values (e.g. structures and floating
+     point types) are left alone, because they would be too complicated
+     to correct.  */
+
+  if (var->endian != TARGET_BYTE_ORDER)
+    {
+      gdb_byte *array = value_contents_raw (val);
+      struct type *type = check_typedef (value_enclosing_type (val));
+      switch (TYPE_CODE (type))
+	{
+	case TYPE_CODE_INT:
+	case TYPE_CODE_PTR:
+	  /* Reverse the bytes.  */
+	  for (i = 0, j = TYPE_LENGTH (type) - 1; i < j; i++, j--)
+	    {
+	      temp = array[j];
+	      array[j] = array[i];
+	      array[i] = temp;
+	    }
+	  break;
+	}
+    }
+
   return val;
 }
 
@@ -809,6 +844,7 @@ set_internalvar (struct internalvar *var
      long.  */
   xfree (var->value);
   var->value = newval;
+  var->endian = TARGET_BYTE_ORDER;
   release_value (newval);
   /* End code which must not call error().  */
 }
@@ -877,7 +913,8 @@ show_convenience (char *ignore, int from
 	  varseen = 1;
 	}
       printf_filtered (("$%s = "), var->name);
-      value_print (var->value, gdb_stdout, 0, Val_pretty_default);
+      value_print (value_of_internalvar (var), gdb_stdout,
+		   0, Val_pretty_default);
       printf_filtered (("\n"));
     }
   if (!varseen)
Index: src/gdb/value.h
===================================================================
--- src.orig/gdb/value.h	2006-02-01 23:14:10.000000000 +0000
+++ src/gdb/value.h	2006-03-30 11:17:29.000000000 +0100
@@ -245,6 +245,7 @@ struct internalvar
   struct internalvar *next;
   char *name;
   struct value *value;
+  int endian;
 };
 
 \f