Bug 840723: Print js::Rooted<jsid> and related classes correctly in non-DEBUG builds. r=sfink

js/src/gdb/mozilla/Root.py

@@ -18,17 +18,38 @@ class Common(object):
     # the template member holds the referent directly.
     handle = False
 
-    def __init__(self, value, cache):
+    # Initialize a pretty-printer for |value|, using |cache|.
+    #
+    # If given, |content_printer| is a pretty-printer constructor to use for
+    # this handle/root/etc.'s referent. Usually, we can just omit this argument
+    # and let GDB choose a pretty-printer for the referent given its type, but
+    # when the referent is a typedef of an integral type (say, |jsid| in a
+    # non-|DEBUG| build), the GNU toolchain (at least) loses the typedef name,
+    # and all we know about the referent is its fundamental integer type ---
+    # |js::Rooted<jsid>|, for example, appears in GDB as |js::Rooted<long>| ---
+    # and we are left with no way to choose a meaningful pretty-printer based on
+    # the type of the referent alone. However, because we know that the only
+    # integer type for which |js::Rooted| is likely to be instantiated is
+    # |jsid|, we *can* register a pretty-printer constructor for the full
+    # instantiation |js::Rooted<long>|. That constructor creates a |js::Rooted|
+    # pretty-printer, and explicitly specifies the constructor for the referent,
+    # using this initializer's |content_printer| argument.
+    def __init__(self, value, cache, content_printer=None):
         self.value = value
+        self.cache = cache
+        self.content_printer = content_printer
     def to_string(self):
         ptr = self.value[self.member]
         if self.handle:
             ptr = ptr.dereference()
-        # As of 2012-11, GDB suppresses printing pointers in replacement values;
-        # see http://sourceware.org/ml/gdb/2012-11/msg00055.html That means that
-        # simply returning the 'ptr' member won't work. Instead, just invoke
-        # GDB's formatter ourselves.
-        return str(ptr)
+        if self.content_printer:
+            return self.content_printer(ptr, self.cache).to_string()
+        else:
+            # As of 2012-11, GDB suppresses printing pointers in replacement
+            # values; see http://sourceware.org/ml/gdb/2012-11/msg00055.html
+            # That means that simply returning the 'ptr' member won't work.
+            # Instead, just invoke GDB's formatter ourselves.
+            return str(ptr)
 
 @template_pretty_printer("js::Rooted")
 class Rooted(Common):

js/src/gdb/mozilla/jsid.py

@@ -2,6 +2,7 @@
 
 import gdb
 import mozilla.prettyprinters
+import mozilla.Root
 
 from mozilla.prettyprinters import pretty_printer
 
@@ -52,3 +53,15 @@ class jsid(object):
         else:
             body = "<unrecognized>"
         return '$jsid(%s)' % (body,)
+
+# Hard-code the referent type pretty-printer for jsid roots and handles.
+# See the comment for mozilla.Root.Common.__init__.
+@pretty_printer('js::Rooted<long>')
+def RootedJSID(value, cache):
+    return mozilla.Root.Rooted(value, cache, jsid)
+@pretty_printer('JS::Handle<long>')
+def HandleJSID(value, cache):
+    return mozilla.Root.Handle(value, cache, jsid)
+@pretty_printer('JS::MutableHandle<long>')
+def MutableHandleJSID(value, cache):
+    return mozilla.Root.MutableHandle(value, cache, jsid)

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

@@ -10,6 +10,9 @@ FRAGMENT(Root, null) {
 
 void callee(JS::Handle<JSObject *> obj, JS::MutableHandle<JSObject *> mutableObj)
 {
+  // Prevent the linker from unifying this function with others that are
+  // equivalent in machine code but not type.
+  fprintf(stderr, "Called " __FILE__ ":callee\n");
   breakpoint();
 }
 

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

@@ -17,3 +17,20 @@ FRAGMENT(jsid, simple) {
   (void) void_id;
   (void) object_id;
 }
+
+void
+jsid_handles(JS::Handle<jsid> jsid_handle,
+             JS::MutableHandle<jsid> mutable_jsid_handle)
+{
+  // Prevent the linker from unifying this function with others that are
+  // equivalent in machine code but not type.
+  fprintf(stderr, "Called " __FILE__ ":jsid_handles\n");
+  breakpoint();
+}
+
+FRAGMENT(jsid, handles) {
+  js::Rooted<JSString *> string(cx, JS_NewStringCopyZ(cx, "shovel"));
+  js::Rooted<JSString *> interned(cx, JS_InternJSString(cx, string));
+  js::Rooted<jsid> string_id(cx, INTERNED_STRING_TO_JSID(cx, interned));
+  jsid_handles(string_id, &string_id);
+}

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

@@ -8,3 +8,8 @@ assert_pretty('string_id', '$jsid("moon")')
 assert_pretty('int_id', '$jsid(1729)')
 assert_pretty('void_id', 'JSID_VOID')
 assert_pretty('object_id', '$jsid((JSObject *)  [object global] delegate)')
+
+run_fragment('jsid.handles')
+
+assert_pretty('jsid_handle',         '$jsid("shovel")')
+assert_pretty('mutable_jsid_handle', '$jsid("shovel")')