GDB: Handy commands for debugging DOM nodes

dom node show somenodeptr
dom node walk somenodeptr
dom document show somedocptr

Load with 'source /path/to/libdom/gdb/libdom.py' when inside gdb.

1 files changed, 157 insertions, 0 deletions

diff --git a/gdb/libdom.py b/gdb/libdom.py
new file mode 100644
index 00000000..65286e3d
--- /dev/null
+++ b/gdb/libdom.py
@@ -0,0 +1,157 @@
+# LibDOM related commands and utilities for gdb
+
+import gdb
+
+def dom_get_type_ptr(typename):
+    return gdb.lookup_type(typename).pointer()
+
+def dom_node_at(ptr):
+    nodetype = dom_get_type_ptr("dom_node_internal")
+    return ptr.cast(nodetype).dereference()
+
+def dom_document_at(ptr):
+    doctype = dom_get_type_ptr("dom_document")
+    return ptr.cast(doctype).dereference()
+
+def dom_node_type(node):
+    return node["type"]
+
+def dom_node_refcnt(node):
+    return node["base"]["refcnt"]
+
+def lwc_string_value(strptr):
+    cptr = strptr+1
+    charptr = cptr.cast(dom_get_type_ptr("char"))
+    return charptr.string()
+
+def dom_string__is_intern(intstr):
+    return str(intstr['type']) == "DOM_STRING_INTERNED"
+
+def cdata_string_value(cdata):
+    cptr = cdata['ptr']
+    charptr = cptr.cast(dom_get_type_ptr("char"))
+    return charptr.string()
+
+def dom_string_value(stringptr):
+    intstr = stringptr.cast(dom_get_type_ptr("dom_string_internal")).dereference()
+    if intstr.address == gdb.parse_and_eval("(dom_string_internal*)0"):
+        return ""
+    if dom_string__is_intern(intstr):
+        return lwc_string_value(intstr['data']['intern'])
+    else:
+        return cdata_string_value(intstr['data']['cdata'])
+
+def dom_node_name(node):
+    namestr = node["name"]
+    return " '%s'" % dom_string_value(namestr)
+
+def dom_node_pending_offset():
+    return gdb.parse_and_eval("(int)&((struct dom_node_internal *)0)->pending_list")
+
+def dom_print_node(node, prefix = ""):
+    print("%s%s @ %s [%s]%s" % (prefix, dom_node_type(node), 
+                                node.address, dom_node_refcnt(node),
+                                dom_node_name(node)))
+
+def dom_walk_tree(node, prefix = ""):
+    dom_print_node(node, prefix)
+    current = node['first_child'].dereference()
+    while current.address != 0:
+        dom_walk_tree(current, "%s  " % prefix)
+        current = current['next'].dereference()
+
+def dom_document_show(doc):
+    print "Node Tree:"
+    node = dom_node_at(doc.address)
+    dom_walk_tree(node, "  ")
+    pending = doc['pending_nodes']
+    if pending['next'] != pending.address:
+        print "Pending Node trees:"
+        current_list_entry = pending['next']
+        while current_list_entry is not None:
+            voidp = current_list_entry.cast(dom_get_type_ptr("void"))
+            voidp = voidp - dom_node_pending_offset()
+            node = dom_node_at(voidp)
+            dom_walk_tree(node, "  ")
+            current_list_entry = node['pending_list']['next']
+            if current_list_entry == pending.address:
+                current_list_entry = None
+    
+
+class DOMCommand(gdb.Command):
+    """DOM related commands"""
+
+    def __init__(self):
+        gdb.Command.__init__(self, "dom", gdb.COMMAND_DATA,
+                             gdb.COMPLETE_COMMAND, True)
+
+class DOMNodeCommand(gdb.Command):
+    """DOMNode related commands"""
+
+    def __init__(self):
+        gdb.Command.__init__(self, "dom node", gdb.COMMAND_DATA,
+                             gdb.COMPLETE_COMMAND, True)
+
+class DOMDocumentCommand(gdb.Command):
+    """DOMDocument related commands"""
+
+    def __init__(self):
+        gdb.Command.__init__(self, "dom document", gdb.COMMAND_DATA,
+                             gdb.COMPLETE_COMMAND, True)
+
+class DOMNodeShowCommand(gdb.Command):
+    """Show a node at a given address."""
+
+    def __init__(self):
+        gdb.Command.__init__(self, "dom node show", gdb.COMMAND_DATA,
+                             gdb.COMPLETE_NONE, True)
+
+    def invoke(self, arg, from_tty):
+        args = gdb.string_to_argv(arg)
+        self._invoke(*args)
+
+    def _invoke(self, nodeptr):
+        _ptr = gdb.parse_and_eval(nodeptr)
+        node = dom_node_at(_ptr)
+        dom_print_node(node)
+
+class DOMNodeWalkCommand(gdb.Command):
+    """Walk a node tree at a given address."""
+
+    def __init__(self):
+        gdb.Command.__init__(self, "dom node walk", gdb.COMMAND_DATA,
+                             gdb.COMPLETE_NONE, True)
+
+    def invoke(self, arg, from_tty):
+        args = gdb.string_to_argv(arg)
+        self._invoke(*args)
+
+    def _invoke(self, nodeptr):
+        _ptr = gdb.parse_and_eval(nodeptr)
+        node = dom_node_at(_ptr)
+        dom_walk_tree(node)
+
+class DOMDocumentShowCommand(gdb.Command):
+    """Show a document at a given address."""
+
+    def __init__(self):
+        gdb.Command.__init__(self, "dom document show", gdb.COMMAND_DATA,
+                             gdb.COMPLETE_NONE, True)
+
+    def invoke(self, arg, from_tty):
+        args = gdb.string_to_argv(arg)
+        self._invoke(*args)
+
+    def _invoke(self, docptr):
+        _ptr = gdb.parse_and_eval(docptr)
+        doc = dom_document_at(_ptr)
+        dom_document_show(doc)
+
+DOMCommand()
+
+DOMNodeCommand()
+DOMNodeShowCommand()
+DOMNodeWalkCommand()
+
+DOMDocumentCommand()
+DOMDocumentShowCommand()