Re: [PATCH] Compare contents when evaluating an array watchpoint

[Andrew Cagney <ac131313@redhat.com>]

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Klee,

Looking through this thread, the technical issues appear to have been 
resolved.  You should probably ping the maintainers.

Andrew

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From: Klee Dienes <klee@apple.com>
To: gdb-patches@sources.redhat.com
Subject: [PATCH] Compare contents when evaluating an array watchpoint
Date: Sun, 6 Oct 2002 05:16:39 -0400
Message-ID: <51EACEDC-D90C-11D6-9330-00039396EEB8@apple.com>

The following patch allows one to set watchpoints on arrays, and have 
the watchpoint triggered if any element in the array changes.  Without 
the patch, the C value_equal semantics causes the address of the array 
to be checked for change, not the contents --- resulting in a 
watchpoint that can never be hit.

This is particularly useful if one wants to do commands like watch 
{char[80]} 0xfff0000, or similar, in order to watch an arbitrary region 
of memory.

2002-08-06  Klee Dienes  <kdienes@bluegill.localnet>

         * breakpoint.c (watchpoint_equal): New function.  Like
         value_equal, but arrays only count as "equal" if they have the
         same contents.
         (watchpoint_check): Update to use watchpoint_equal.

diff -u -r1.1.1.21 -r1.47
--- breakpoint.c	2002/09/26 20:56:41	1.1.1.21
+++ breakpoint.c	2002/10/06 09:07:23	1.47
@@ -2359,6 +2448,34 @@
    return bs;
  }

+/* Like value_equal, but two arrays are only considered equal if their
+   contents are equal. */
+
+static int
+watchpoint_equal (struct value *arg1, struct value *arg2)
+{
+  register int len;
+  register char *p1, *p2;
+
+  if ((TYPE_CODE (VALUE_TYPE (arg1)) == TYPE_CODE_ARRAY)
+      && (TYPE_CODE (VALUE_TYPE (arg2)) == TYPE_CODE_ARRAY))
+    {
+      int len = TYPE_LENGTH (VALUE_TYPE (arg1));
+      if (TYPE_LENGTH (VALUE_TYPE (arg1)) != TYPE_LENGTH (VALUE_TYPE 
(arg2)))
+	return 0;
+      p1 = VALUE_CONTENTS (arg1);
+      p2 = VALUE_CONTENTS (arg2);
+      while (--len >= 0)
+	{
+	  if (*p1++ != *p2++)
+	    break;
+	}
+      return len < 0;
+    }
+
+  return value_equal (arg1, arg2);
+}
+
  /* Possible return values for watchpoint_check (this can't be an enum
     because of check_errors).  */
  /* The watchpoint has been deleted.  */
@@ -2417,7 +2535,7 @@

        struct value *mark = value_mark ();
        struct value *new_val = evaluate_expression 
(bs->breakpoint_at->exp);
-      if (!value_equal (b->val, new_val))
+      if (!watchpoint_equal (b->val, new_val))
  	{
  	  release_value (new_val);