According to v8.h, "the returned handle is valid until this TryCatch
block has been destroyed". This is incorrect, as can be demonstrated
with the test below. In practice the return value lives no longer and
no shorter than the active HandleScope at the time these methods are
called. An issue has been opened about this in the V8 bug tracker:
https://bugs.chromium.org/p/v8/issues/detail?id=10537.
```rust
fn try_catch_bad_lifetimes() {
let _setup_guard = setup();
let mut isolate = v8::Isolate::new(Default::default());
let mut hs = v8::HandleScope::new(&mut isolate);
let scope = hs.enter();
let context = v8::Context::new(scope);
let mut cs = v8::ContextScope::new(scope, context);
let scope = cs.enter();
let caught_msg_2 = {
let mut try_catch = v8::TryCatch::new(scope);
let try_catch = try_catch.enter();
let caught_msg_1 = {
let mut hs = v8::HandleScope::new(scope);
let scope = hs.enter();
// Throw exception #1.
let msg_1 = v8::String::new(scope, "BOOM!").unwrap();
let exc_1 = v8::Exception::type_error(scope, msg_1);
scope.isolate().throw_exception(exc_1);
// Catch exception #1.
let caught_msg_1 = try_catch.message().unwrap();
let caught_str_1 =
caught_msg_1.get(scope).to_rust_string_lossy(scope);
assert!(caught_str_1.contains("BOOM"));
// Move `caught_msg_1` out of the HandleScope it was created in.
// The borrow checker allows this because `caught_msg_1`'s
// lifetime is contrained to not outlive the TryCatch, but it is
// allowed to outlive the HandleScope that was active when the
// exception was caught.
caught_msg_1
};
// Next line crashes.
let caught_str_1 =
caught_msg_1.get(scope).to_rust_string_lossy(scope);
assert!(caught_str_1.contains("BOOM"));
// Throws exception #2.
let msg_2 = v8::String::new(scope, "DANG!").unwrap();
let exc_2 = v8::Exception::type_error(scope, msg_2);
scope.isolate().throw_exception(exc_2);
// Catch exception #2.
let caught_msg_2 = try_catch.message().unwrap();
let caught_str_2 =
caught_msg_2.get(scope).to_rust_string_lossy(scope);
assert!(caught_str_2.contains("DANG"));
// Move `caught_msg_2` out of the extent of the TryCatch, but still
// within the extent of its HandleScope. This is unnecessarily
// rejected at compile time.
caught_msg_2
};
let caught_str_2 =
caught_msg_2.get(scope).to_rust_string_lossy(scope);
assert!(caught_str_2.contains("DANG"));
}
```
* Add `SharedPtr` as a nullable sibling to `SharedRef`.
* Add `Borrow`, `AsRef` and `AsMut` implementations as appropriate.
* `SharedRef<T>` now derefs to `T` rather than to `UnsafeCell<T>`.
* `array_buffer::BackingStore` now derefs to `[Cell<u8>]`.
In v8.h, not all heap object classes actually derive from `v8::Data`,
but this seems to be a mistake, because this hierarchy does definitely
exists in V8's internal source code.
The file naming in the current src/inspector/ directory is inconsistent and difficult to
navigate. It will be simpler if we just put them all in one place since they're rather
interconnected.
This doesn't really follow the current V8 API (it's pretty close to how
V8 used to be back in 2012 though.) However:
1. The C++ API is very C++-y and doesn't carry over well to Rust, and
2. It addresses the immediate need of being able to take heap snapshots.
Refs #298
This function acquires a mutex lock which, prior to this patch, would be
unlocked _after_ releasing the IsolateAnnex memory allocation where the
mutex was stored.
The `get_current_context()` and `get_entered_or_microtask_context()`
methods now return `Option<Local<Context>>` to reflect that an isolate
may not have entered any context.
They're also moved from `Isolate` to `struct Entered` because it turns
out that the underlying V8 API calls actually create new local handles,
hence they should only be used inside an active HandleScope.
The `InContext` trait has been removed.
A test exercising `ContextScope` and the `get_*_context()` methods
mentioned above was added.
Closes: #248.
