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# Pretty-printers and utilities for SpiderMonkey rooting templates:
# Rooted, Handle, MutableHandle, etc.
import mozilla.prettyprinters
from mozilla.prettyprinters import pretty_printer, template_pretty_printer
# Forget any printers from previous loads of this module.
mozilla.prettyprinters.clear_module_printers(__name__)
# Common base class for all the rooting template pretty-printers. All these
# templates have one member holding the referent (or a pointer to it), so
# there's not much to it.
class Common(object):
# The name of the template member holding the referent.
member = 'ptr'
# If True, this is a handle type, and should be dereferenced. If False,
# the template member holds the referent directly.
handle = False
# If True, we should strip typedefs from our referent type. (Rooted<T>
# uses template magic that gives the referent a noisy type.)
strip_typedefs = False
# 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()
if self.strip_typedefs:
ptr = ptr.cast(ptr.type.strip_typedefs())
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):
strip_typedefs = True
@template_pretty_printer("JS::Handle")
class Handle(Common):
handle = True
@template_pretty_printer("JS::MutableHandle")
class MutableHandle(Common):
handle = True
@template_pretty_printer("js::BarrieredBase")
class BarrieredBase(Common):
member = 'value'
# Return the referent of a HeapPtr, Rooted, or Handle.
def deref(root):
tag = root.type.strip_typedefs().tag
if not tag:
raise TypeError("Can't dereference type with no structure tag: %s" % (root.type,))
elif tag.startswith('js::HeapPtr<'):
return root['value']
elif tag.startswith('JS::Rooted<'):
return root['ptr']
elif tag.startswith('JS::Handle<'):
return root['ptr']
elif tag.startswith('js::GCPtr<'):
return root['value']
else:
raise NotImplementedError("Unrecognized tag: " + tag)
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