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Valentin Shergin
57dd48b246
Summary: Exceptions in C++ work quite differently from exceptions in other languages. To make exceptions actually work **correctly** all the code needs to be written with "exceptions in mind" (e.g., see https://www.stroustrup.com/except.pdf). In short, if the code is not "exceptions ready", throwing an exception causes memory leaks, dangling pointers, and invariant violations all over the place, which will probably cause another crashes down the road (which will be especially hard to investigate and attribute to the original issue). Fabric Core (Layout, Props parsing, ShadowNodes management, and so on) does not use exceptions because in most (all?) the cases the exception is now recoverable. So, if a program detects some internal state invariant violation or missing some resource, *logically* it's fatal. We also don't want to pay code-size and performance tax for exception support, so that's why we don't use them. It's just not the right fit for Fabric Core. This does not mean that exceptions don't happen though. C++ standard library can throw them... sometimes. And if our library is compiled with exceptions enabled (still the case, unfortunately), an exception can bubble to JavaScript code and losing all context down the road. And it's hard to investigate such crashes. To isolate those occasional exceptions inside C++ core we are marking all C++/JS boundaries with `noexcept` that stops the bubbling. I hope that will give us much more informative crash reports. Changelog: [Internal] Fabric-specific internal change. Reviewed By: sammy-SC Differential Revision: D23787492 fbshipit-source-id: 0822dbf36fc680c15b02b5cd0f2d87328296b642