[libcxx-commits] [PATCH] D115730: [libc++] Add a helper class to write code with the strong exception guarantee

[Louis Dionne via Phabricator via libcxx-commits]

ldionne added a comment.

In D115730#3203479 <https://reviews.llvm.org/D115730#3203479>, @Quuxplusone wrote:

> @ldionne: I'd still prefer the version I showed in https://reviews.llvm.org/D115730?id=394248#inline-1106466 where the object doesn't have a `completed` data member at all (so it would better be named `__on_scope_exit` rather than `__transaction`). I'd also be interested in seeing a godbolt or something showing which approach gives better codegen. Naïvely, I would expect my preferred version would be no worse, and maybe a tiny bit better, because it gives the optimizer more freedom to rearrange the stack frame. But the reason I prefer it is for simplicity/readability: I think the `set_completed`/`__complete` thing is easy to mess up.

I have a strong distaste for managing the `bool completed` and having to enclose all the rollback code in `if (!completed)`. IMO that's a lot easier to mess up than just making sure a `__complete()` method is called. Since this simple helper is really tailored for exception handling (it's purely a means to remove `#if _LIBCPP_NO_EXCEPTIONS`), I'd rather keep as-is.


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  https://reviews.llvm.org/D115730/new/

https://reviews.llvm.org/D115730