Here is a description of the background and design of split window in Chrome and V8:
https://docs.google.com/a/google.com/Doc?id=chhjkpg_47fwddxbfr
This change list splits the window object into two parts: 1) an inner window object used as the global object of contexts; 2) an outer window object exposed to JavaScript and accessible by the name 'window'. Firefox did it awhile ago, here are some discussions: https://wiki.mozilla.org/Gecko:SplitWindow. One additional benefit of splitting window in Chrome is that accessing global variables don't need security checks anymore, it can improve applications that use many global variables.
V8 support of split window:
There are a small number of changes on V8 api to support split window:
Security context is removed from V8, so does related API functions;
A global object can be detached from its context and reused by a new context;
Access checks on an object template can be turned on/off by default;
An object can turn on its access checks later;
V8 has a new object type, ApiGlobalObject, which is the outer window object type. The existing JSGlobalObject becomes the inner window object type. Security checks are moved from JSGlobalObject to ApiGlobalObject. ApiGlobalObject is the one exposed to JavaScript, it is accessible through Context::Global(). ApiGlobalObject's prototype is set to JSGlobalObject so that property lookups are forwarded to JSGlobalObject. ApiGlobalObject forwards all other property access requests to JSGlobalObject, such as SetProperty, DeleteProperty, etc.
Security token is moved to a global context, and ApiGlobalObject has a reference to its global context. JSGlobalObject has a reference to its global context as well. When accessing properties on a global object in JavaScript, the domain security check is performed by comparing the security token of the lexical context (Top::global_context()) to the token of global object's context. The check is only needed when the receiver is a window object, such as 'window.document'. Accessing global variables, such as 'var foo = 3; foo' does not need checks because the receiver is the inner window object.
When an outer window is detached from its global context (when a frame navigates away from a page), it is completely detached from the inner window. A new context is created for the new page, and the outer global object is reused. At this point, the access check on the DOMWindow wrapper of the old context is turned on. The code in old context is still able to access DOMWindow properties, but it has to go through domain security checks.
It is debatable on how to implement the outer window object. Currently each property access function has to check if the receiver is ApiGlobalObject type. This approach might be error-prone that one may forget to check the receiver when adding new functions. It is unlikely a performance issue because accessing global variables are more common than 'window.foo' style coding.
I am still working on the ARM port, and I'd like to hear comments and suggestions on the best way to support it in V8.
Review URL: http://codereview.chromium.org/7366
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@540 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
underlying string representation of the two strings involved.
- Renamed ascii and two byte string classes to sequential ascii and
sequential two byte, and renamed IsAscii and friends to
IsAsciiRepresentation. This is to make a clear distinction between
strings with an ascii/two-byte representation, of which there is
four, and flat sequential ascii/two-byte string.
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@474 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
- Simplified frame entry and frame exit code.
- Added ArgumentsAdaptorTrampoline and check for matching argument counts in the InvokePrologue.
- Removed definition and uses of USE_OLD_CALLING_CONVENTIONS.
- Changed MacroAssembler::InvokeBuiltin to match ia32 version.
- Start introducing convenience instructions in the ARM assembler as needed. These instructions take all Register parameters to avoid extra typing of "Operand(reg)".
To keep the architectures in sync these changes have been made to the ia32 files:
- Changed MacroAssembler::EnterFrame(StackFrame::Type type) to MacroAssembler::EnterInternalFrame().
These parts are still missing:
- unimplemented: Builtins::Generate_FunctionApply - large limit
- unimplemented: Builtins::Generate_ArgumentsAdaptorTrampoline - non-function call
- The files have not been lint'd yet.
Review URL: http://codereview.chromium.org/1930
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@289 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
- Fixed mozilla test breakage caused by python's obscure module
loading rules.
- Made sure test.py propagates test failures out as the exit code of
the script.
- Remove runtime calls to get number constants. Remove Heap roots for
some special numbers.
- Fix typo in accessors.h.
- Changes CopyMap to not copy descriptors. Adds
CopyMapRemoveTransitions that copies non-transition descriptors.
Changes interface of DescriptorArray::Copy operations to simplify
them.
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@21 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Added better test support.
Added load, quit and version functions to the shell sample so it's easier to run benchmarks and tests.
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
In the shell sample don't print the result of executing a script, only
evaluating expressions.
Fixed issue when building samples on Windows using a shared V8
library. Added visibility option on Linux build which makes the
generated library 18% smaller.
Changed build system to accept multiple build modes in one build and
generate seperate objects, libraries and executables for each mode.
Removed deferred negation optimization (a * -b => -(a * b)) since this
visibly changes operand conversion order.
Improved parsing performance by introducing stack guard in preparsing.
Without a stack guard preparsing always bails out with stack overflow.
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Extended the shell sample with a --runtime-flags option.
Added Visual Studio project files for the shell.cc and process.cc samples.
git-svn-id: http://v8.googlecode.com/svn/trunk@14 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Added a few samples and support for building them. The samples include a simple shell that can be used to benchmark and test V8.
Changed V8::GetVersion to return the version as a string.
Added source for lazily loaded scripts to snapshots and made serialization non-destructive.
Improved ARM support by fixing the write barrier code to use aligned loads and stores and by removing premature locals optimization that relied on broken support for callee-saved registers (removed).
Refactored the code for marking live objects during garbage collection and the code for allocating objects in paged spaces. Introduced an abstraction for the map word of a heap-allocated object and changed the memory allocator to allocate executable memory only for spaces that may contain code objects.
Moved StringBuilder to utils.h and ScopedLock to platform.h, where they can be used by debugging and logging modules. Added thread-safe message queues for dealing with debugger events.
Fixed the source code reported by toString for certain builtin empty functions and made sure that the prototype property of a function is enumerable.
Improved performance of converting values to condition flags in generated code.
Merged disassembler-{arch} files.
git-svn-id: http://v8.googlecode.com/svn/trunk@8 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
