Bug 822563: Pretty-print references to JSObject and its subclasses. r=sfink

js/src/gdb/mozilla/JSObject.py

@@ -3,7 +3,7 @@
 import gdb
 import mozilla.JSString
 import mozilla.prettyprinters as prettyprinters
-from mozilla.prettyprinters import ptr_pretty_printer
+from mozilla.prettyprinters import ptr_pretty_printer, ref_pretty_printer
 from mozilla.Root import deref
 
 prettyprinters.clear_module_printers(__name__)
@@ -19,9 +19,9 @@ class JSObjectTypeCache(object):
 # JSFunction has JSObject as a base class.
 
 @ptr_pretty_printer('JSObject')
-class JSObjectPtr(prettyprinters.Pointer):
+class JSObjectPtrOrRef(prettyprinters.Pointer):
     def __init__(self, value, cache):
-        super(JSObjectPtr, self).__init__(value, cache)
+        super(JSObjectPtrOrRef, self).__init__(value, cache)
         if not cache.mod_JSObject:
             cache.mod_JSObject = JSObjectTypeCache(value, cache)
         self.otc = cache.mod_JSObject
@@ -34,9 +34,15 @@ class JSObjectPtr(prettyprinters.Pointer):
         is_delegate = bool(flags & self.otc.flag_DELEGATE)
         name = None
         if class_name == 'Function':
-            function = self.value.cast(self.otc.func_ptr_type)
+            if self.value.type.code == gdb.TYPE_CODE_PTR:
+                function = self.value.cast(self.otc.func_ptr_type)
+            elif self.value.type.code == gdb.TYPE_CODE_REF:
+                function = self.value.address.cast(self.otc.func_ptr_type)
             atom = deref(function['atom_'])
             name = str(atom) if atom else '<unnamed>'
         return '[object %s%s]%s' % (class_name,
                                     ' ' + name if name else '',
                                     ' delegate' if is_delegate else '')
+
+@ref_pretty_printer('JSObject')
+def JSObjectRef(value, cache): return JSObjectPtrOrRef(value, cache)

js/src/gdb/mozilla/prettyprinters.py

@@ -45,6 +45,20 @@ def ptr_pretty_printer(type_name):
         return fn
     return add
 
+# a dictionary mapping gdb.Type tags to pretty-printer functions for
+# references to that type.
+ref_printers_by_tag = {}
+
+# A decorator: add the decoratee as a pretty-printer lookup function for
+# references to instances of types named |type_name|.
+def ref_pretty_printer(type_name):
+    def add(fn):
+        check_for_reused_pretty_printer(fn)
+        add_to_subprinter_list(fn, "ref-to-" + type_name)
+        ref_printers_by_tag[type_name] = fn
+        return fn
+    return add
+
 # a dictionary mapping the template name portion of gdb.Type tags to
 # pretty-printer functions for instantiations of that template.
 template_printers_by_tag = {}
@@ -83,7 +97,8 @@ def pretty_printer_for_regexp(pattern, name):
 #
 #   clear_module_printers(__name__)
 def clear_module_printers(module_name):
-    global printers_by_tag, ptr_printers_by_tag, template_printers_by_tag, printers_by_regexp
+    global printers_by_tag, ptr_printers_by_tag, ref_printers_by_tag
+    global template_printers_by_tag, printers_by_regexp
 
     # Remove all pretty-printers defined in the module named |module_name|
     # from d.
@@ -101,6 +116,7 @@ def clear_module_printers(module_name):
 
     clear_dictionary(printers_by_tag)
     clear_dictionary(ptr_printers_by_tag)
+    clear_dictionary(ref_printers_by_tag)
     clear_dictionary(template_printers_by_tag)
 
     # Iterate over printers_by_regexp, deleting entries from the given module.
@@ -226,28 +242,31 @@ def lookup_for_objfile(objfile):
                     return f(value, cache)
             return None
 
+        def check_table_by_type_name(table, t):
+            if t.code == gdb.TYPE_CODE_TYPEDEF:
+                return check_table(table, str(t))
+            elif t.code == gdb.TYPE_CODE_STRUCT and t.tag:
+                return check_table(table, t.tag)
+            else:
+                return None
+
         for t in implemented_types(value.type):
             if t.code == gdb.TYPE_CODE_PTR:
                 for t2 in implemented_types(t.target()):
-                    if t2.code == gdb.TYPE_CODE_TYPEDEF:
-                        p = check_table(ptr_printers_by_tag, str(t2))
-                    elif t2.code == gdb.TYPE_CODE_STRUCT and t2.tag:
-                        p = check_table(ptr_printers_by_tag, t2.tag)
-                    else:
-                        p = None
+                    p = check_table_by_type_name(ptr_printers_by_tag, t2)
+                    if p: return p
+            elif t.code == gdb.TYPE_CODE_REF:
+                for t2 in implemented_types(t.target()):
+                    p = check_table_by_type_name(ref_printers_by_tag, t2)
                     if p: return p
             else:
-                if t.code == gdb.TYPE_CODE_TYPEDEF:
-                    p = check_table(printers_by_tag, str(t))
-                elif t.code == gdb.TYPE_CODE_STRUCT and t.tag:
+                p = check_table_by_type_name(printers_by_tag, t)
+                if p: return p
+                if t.code == gdb.TYPE_CODE_STRUCT and t.tag:
                     m = template_regexp.match(t.tag)
                     if m:
                         p = check_table(template_printers_by_tag, m.group(1))
-                    else:
-                        p = check_table(printers_by_tag, t.tag)
-                else:
-                    p = None
-                if p: return p
+                        if p: return p
 
         # Failing that, look for a printer in printers_by_regexp. We have
         # to scan the whole list, so regexp printers should be used
@@ -275,6 +294,8 @@ def lookup_for_objfile(objfile):
 # pointers, by declining to construct a pretty-printer for them at all.
 # Derived classes may simply assume that self.value is non-null.
 #
+# To help share code, this class can also be used with reference types.
+#
 # This class provides the following methods, which subclasses are free to
 # override:
 #
@@ -291,7 +312,8 @@ def lookup_for_objfile(objfile):
 class Pointer(object):
     def __new__(cls, value, cache):
         # Don't try to provide pretty-printers for NULL pointers.
-        if value == 0: return None
+        if value.type.code == gdb.TYPE_CODE_PTR and value == 0:
+            return None
         return super(Pointer, cls).__new__(cls)
 
     def __init__(self, value, cache):
@@ -301,7 +323,10 @@ class Pointer(object):
     def to_string(self):
         # See comment above.
         assert not hasattr(self, 'display_hint') or self.display_hint() != 'string'
-        address = self.value.cast(self.cache.void_ptr_t)
+        if self.value.type.code == gdb.TYPE_CODE_PTR:
+            address = self.value.cast(self.cache.void_ptr_t)
+        elif self.value.type.code == gdb.TYPE_CODE_REF:
+            address = '@' + str(self.value.address.cast(self.cache.void_ptr_t))
         try:
             summary = self.summary()
         except gdb.MemoryError as r:

js/src/gdb/tests/test-JSObject.cpp

@@ -10,6 +10,9 @@ FRAGMENT(JSObject, simple) {
   js::Rooted<JSFunction *> funcPtr(cx, JS_NewFunction(cx, (JSNative) 1, 0, 0,
                                                       JS_GetGlobalObject(cx), "formFollows"));
 
+  JSObject &plainRef = *plain;
+  JSFunction &funcRef = *funcPtr;
+
   breakpoint();
 
   (void) glob;
@@ -17,6 +20,8 @@ FRAGMENT(JSObject, simple) {
   (void) func;
   (void) anon;
   (void) funcPtr;
+  (void) plainRef;
+  (void) funcRef;
 }
 
 FRAGMENT(JSObject, null) {
@@ -26,4 +31,3 @@ FRAGMENT(JSObject, null) {
 
   (void) null;
 }
-

js/src/gdb/tests/test-JSObject.py

@@ -1,6 +1,8 @@
 # Printing JSObjects.
 
 assert_subprinter_registered('SpiderMonkey', 'ptr-to-JSObject')
+assert_subprinter_registered('SpiderMonkey', 'ref-to-JSObject')
+
 run_fragment('JSObject.simple')
 
 # These patterns look a little strange because of prolog.py's 'set print
@@ -13,3 +15,6 @@ assert_pretty('plain', '(JSObject *)  [object Object]')
 assert_pretty('func', '(JSObject *)  [object Function "dys"]')
 assert_pretty('anon', '(JSObject *)  [object Function <unnamed>]')
 assert_pretty('funcPtr', '(JSFunction *)  [object Function "formFollows"]')
+
+assert_pretty('plainRef', '(JSObject &) @ [object Object]')
+assert_pretty('funcRef', '(JSFunction &) @ [object Function "formFollows"]')

js/src/gdb/tests/test-prettyprinters.py

@@ -16,3 +16,7 @@ assert_eq(implemented_type_names('e'), ['E', 'C', 'D'])
 assert_eq(implemented_type_names('e_'), ['E_', 'E', 'C', 'D'])
 assert_eq(implemented_type_names('f'), ['F', 'C', 'D'])
 assert_eq(implemented_type_names('h'), ['H', 'F', 'G', 'C', 'D'])
+
+# Check that our pretty-printers aren't interfering with printing other types.
+assert_pretty('10', '10')
+assert_pretty('(void*) 0', '') # Because of 'set print address off'