Fix a regression that was introduced in commit ce04c726 after the
upgrade to V8 3.24.
The new weak persistent handle API no longer gives you the original
persistent but still requires that you clear it inside your weak
callback.
Rearrange the code in src/smalloc.cc to keep track of the persistent
handle with the least amount of pain and try hard to share as much
code as possible between the 'just free it' and 'invoke my callback'
versions of the smalloc API.
Fixes#7309.
Make calls to v8::Isolate::AdjustAmountOfExternalAllocatedMemory() take
special care when negating 32 bits unsigned types like size_t.
Before this commit, values were negated before they got promoted to
64 bits, meaning that on 32 bits architectures, a value like 42 got
cast to 4294967254 instead of -42.
That in turn made the garbage collector start scavenging like crazy
because it thought the system was out of memory.
That's bad enough but calls to AdjustAmountOfExternalAllocatedMemory()
were made from weak callbacks, i.e. at a time when the garbage collector
was already busy. It triggered asserts in debug builds and caused
random crashes and memory corruption in release builds.
The behavior in release builds is arguably a V8 bug and should perhaps
be reported upstream.
Partially fixes#7309 but requires further bug fixes to src/smalloc.cc
that I'll address in a follow-up commit.
Built-in modules should be automatically registered, replacing the
static module list. Add-on modules should also be automatically
registered via DSO constructors. This improves flexibility in adding
built-in modules and is also a prerequisite to pure-C addon modules.
Create a HandleScope before calling the Environment::GetCurrent() that
takes a v8::Isolate* as an argument because it creates a handle with
the call to v8::Isolate::CurrentContext().
This commit makes it possible to use multiple V8 execution contexts
within a single event loop. Put another way, handle and request wrap
objects now "remember" the context they belong to and switch back to
that context when the time comes to call into JS land.
This could have been done in a quick and hacky way by calling
v8::Object::GetCreationContext() on the wrap object right before
making a callback but that leaves a fairly wide margin for bugs.
Instead, we make the context explicit through a new Environment class
that encapsulates everything (or almost everything) that belongs to
the context. Variables that used to be a static or a global are now
members of the aforementioned class. An additional benefit is that
this approach should make it relatively straightforward to add full
isolate support in due course.
There is no JavaScript API yet but that will be added in the near
future.
This work was graciously sponsored by GitHub, Inc.
The C++ API has been changed so the passed length is the byte size of
the data, not the length of the array.
This was done so users need to explicitly define how much memory they
want allocated.
* Change calls to String::New() and String::NewSymbol() to their
respective one-byte, two-byte and UTF-8 counterparts.
* Add a FIXED_ONE_BYTE_STRING macro that takes a string literal and
turns it into a v8::Local<v8::String>.
* Add helper functions that make v8::String::NewFromOneByte() easier to
work with. Said function expects a `const uint8_t*` but almost every
call site deals with `const char*` or `const unsigned char*`. Helps
us avoid doing reinterpret_casts all over the place.
* Code that handles file system paths keeps using UTF-8 for backwards
compatibility reasons. At least now the use of UTF-8 is explicit.
* Remove v8::String::NewSymbol() entirely. Almost all call sites were
effectively minor de-optimizations. If you create a string only once,
there is no point in making it a symbol. If you are create the same
string repeatedly, it should probably be cached in a persistent
handle.
smalloc.alloc now accepts an optional third argument which allows
specifying the type of array that should be allocated. All available
types are now located on smalloc.Types.
* Moved the ToObject check out of smalloc::Alloc and into JS. Direct
usage of that method is for internal use only and so can bypass the
possible coercion.
* Same has been done with smalloc::SliceOnto.
* smalloc::CopyOnto will now throw if passed argument is not an object.
* Remove extra TargetFreeCallback function. There was a use for it when
it was working with a Local<T>, but that code has been removed making
the function superfluous.
SlowBuffer(0) passes NULL instead of doing malloc(0). So when someone
attempted to SlowBuffer(0).slice(0, 1) an assert would fail in
smalloc::SliceOnto.
It's important that the check go where it is because the resulting
Buffer needs to have external array data allocated. In the case a user
tries to slice a zero length Buffer it will also have NULL passed as the
data argument.
Also fixed where the .parent attribute was set for zero length Buffers.
There is no need to track the source of slice if the slice isn't
actually occurring.
It will be confusing if later on we add Buffer#dispose(), and smalloc is
its own cpp api anyways. So instead create a new require('smalloc') to
expose the previous Buffer.alloc/dispose methods, and expose copyOnto
and kMaxLength as well.
Other changes:
* Added documentation and additional tests.
* smalloc::CopyOnto has changed from using assert() to throwing errors
on bad argument values because it is not exposed to the user.
* Minor style fixes.
In fa10b75 the assert to check if data == NULL was remove for
smalloc::Alloc with no callback. It should have also been removed where
a callback is accepted.
No sense in making sure that length == 0 if data == NULL because devs
already have to be responsible for checking that length is the same as
the char* they're passing in.
Fix bug where if dev passed a callback to Alloc then called AllocDispose
it wouldn't bother to pass the data to the callback and instead would
just free it.
This is a big commit that touches just about every file in the src/
directory. The V8 API has changed in significant ways. The most
important changes are:
* Binding functions take a const v8::FunctionCallbackInfo<T>& argument
rather than a const v8::Arguments& argument.
* Binding functions return void rather than v8::Handle<v8::Value>. The
return value is returned with the args.GetReturnValue().Set() family
of functions.
* v8::Persistent<T> no longer derives from v8::Handle<T> and no longer
allows you to directly dereference the object that the persistent
handle points to. This means that the common pattern of caching
oft-used JS values in a persistent handle no longer quite works,
you first need to reconstruct a v8::Local<T> from the persistent
handle with the Local<T>::New(isolate, persistent) factory method.
A handful of (internal) convenience classes and functions have been
added to make dealing with the new API a little easier.
The most visible one is node::Cached<T>, which wraps a v8::Persistent<T>
with some template sugar. It can hold arbitrary types but so far it's
exclusively used for v8::Strings (which was by far the most commonly
cached handle type.)
If the user knows the allocation is no longer needed then the memory can
be manually released.
Currently this will not ClearWeak the Persistent, so the callback will
still run.
If the user passed a ClearWeak callback, and then disposed the object,
the buffer callback argument will == NULL.
smalloc is a simple utility for quickly allocating external memory onto
js objects. This will be used to centralize how memory is managed in
node, and will become the backer for Buffers. So in the future crypto's
SlabBuffer, stream's SlabAllocator will be removed.
Note on the js API: because no arguments are optional the order of
arguments have been placed to match their cc counterparts as closely as
possible.
Ben Noordhuis
Fedor Indutny
Keith M Wesolowski
Trevor Norris