Summary: Storing a strong shared pointer to `ComponentDescriptor` can cause a memory leak. Therefore we enforce all call sides and params to be weak pointers. The only Scheduler preserves a retaining pointer to it (to prevent preliminary deallocation).
Reviewed By: sammy-SC
Differential Revision: D17115540
fbshipit-source-id: fdea7d19f742ff04d5ba5470dd9748a5b226aa7c
Summary:
First of all, seems it's the right thing to do. Fabric C++ code is cross-platfrom and should run on *all* platforms including Windows, Linux, and Mac.
While we don't have a real *production* use cases where we need compilation for desktops, having CXX target is really handy for two reasons:
* It simplifies local test running process. Instead of going to `/fbandroid/` and executing something like `buck test fbsource//xplat/js/react-native-github/ReactCommon/fabric/core:coreAndroid` (note the suffix). We can just do `buck test fbsource//xplat/js/react-native-github/ReactCommon/fabric/core:core` everywhere and it works now out of the box. Running tests with "Apple" flavor never worked for me.
* It allows creating synthetic benchmark tests (using Google Benchmark) that can be used as a rough approximation of code micro-optimizations.
Reviewed By: JoshuaGross
Differential Revision: D15608678
fbshipit-source-id: d2449035685dbca6ab983480f5334ec4ac11cd35
Summary:
This diff restores the original role of StateData as a dummy class that has only one purpose - designate that there is no state associated with the node.
I believe having an abstract StateData class for all data types is not necessary and actually slightly harmful. And here the reasons:
* Having virtual dispatch enabled for classes introduces some overhead, and it should be used only if it is absolutely necessary. In this case, we don't need to have virtual dispatch enabled for Data classes because it's already enabled for State classes; therefore all virtual resolution is done there and that's sufficient. No need to pay for what we don't need.
* Continuing the previous point, yes, we expect some API being exposed for Data classes (such as `getDynamic`), but introducing a base abstract class for that is *not* an idiomatic C++ solution; in C++ it's by design that most of the template contracts are actually duck-typed. This is a well-known design issue/concern that will be addressed with an effort called "Concepts" in C++20. Anyway, we should not use abstract classes as *only* indication of conformance to some interface.
* StateData does not introduce any convenience. As it is clear from several subclass implementations, we don't really use base methods from it.
* The previous issue actually happens especially because of the interface of StateData class. Consider constructor that accepts `folly::dynamic` and does nothing, it actually useless because it's impossible to use it unless it's called inside superclass's constructor. That's the case because C++ does not support virtual dispatch for constructors (for good).
* Avoiding subclassing StateData counter-intuitively enforces the desired conformance to imaginary interface: it does not compile otherwise.
Reviewed By: JoshuaGross
Differential Revision: D15342338
fbshipit-source-id: 1f04f7fc5247499e7cfc09cd4b3cccffdc0b6b06
Valentin Shergin
Samuel Susla
Kevin Gozali
David Vacca