Re: [boost] Proposed SG14 <system_error2> ready for feedback

2018-03-01 18:57 GMT+01:00 Niall Douglas via Boost :

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The github readme at https://github.com/ned14/status-code gives a clear description how I can make use of POSIX and Windows-standard error codes.

It must therefore not be self obvious? Darn. I had thought it very simple, basically with a few obvious tweaks. Not worth much explaining, anyway.

Not obvious to me: especially the templetized codes, and two kinds of type erasure. This part of the design is definitely more complicated than the original . I would expect examples and some rationale. If you choose to describe as a diff from , I would expect all relevant differences to be mentioned in the docs. For instance I can see you use `status_code_domain` rather than `error_category`. This looks like an improvement in clarity. Also, how do you handle error code names without strings? Do i need to define my own string_ref? Similarly, how did you fix the "duplicated globals" problem on Windows? Also, there is this paragraph: The relationship between std::error_code and std::error_condition is confusing to many users reading code based on , specifically when is a comparison between codes *semantic* or *literal*? status_code makes all comparisons *semantic*, *always*. If you want a literal comparison, you can do one by hand by comparing domains and values directly. I fail to see what you mean by "semantic comparison" and "literal comparison". Do they mean comparing error_code to error_category and comparing error_code to error_code respectively?

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Could we have similar short and clear examples illustrating how one can: 1. Create a custom error_category (or equivalent thing) 2. Use parametrized statuc_code

There is a test custom domain at https://github.com/ned14/status-code/blob/master/test/main.cpp#L44.

But how about a mini-tutorial on building a custom code domain whose status code wraps any arbitrary thrown C++ exception? It looks like SG14 and WG21 is going to need one of those in any case.

Any information would be useful, but I think it is more basic things that are insufficiently described. For now, consider it a feedback on what a casual reader will not understand about . Regards, &rzej;