On Thu, Dec 27, 2018 at 12:18:11AM +0100, Branko Čibej wrote: > On 26.12.2018 23:44, Daniel Shahaf wrote: > > Branko Čibej wrote on Wed, 26 Dec 2018 23:37 +0100: > >> On 26.12.2018 23:21, Daniel Shahaf wrote: > >>> Branko Čibej wrote on Wed, 26 Dec 2018 22:41 +0100: > >>>> On 26.12.2018 19:50, Daniel Shahaf wrote: > >>>>> Haven't reviewed the rest of the patch, nor the mapping of > >>>>> svn_error_t::apr_err values to this hierarchy. > >>>> There is just one exception type that encapsulates all of svn_error_t, > >>>> including the apr_err bit; that's 'svn::error'. I have no intention of > >>>> going down the rabbit hole of having one exception type for each > >>>> possible apr_err value! > >>>> > >>> Yeah, that'd be way too much; but I was thinking of two things: > >>> > >>> 1. apr_err can be an errno error code, not just an APR_OS_START_USERERR > >>> code. I don't have the C++ exceptions hierarchy in mind, but I > >>> suspect that when APR_STATUS_IS_EEXIST(err->apr_err), an svn::error > >>> instance is not what people (and 'catch' blocks) will expect. > >> > >> Ah, good point. I hadn't actually thought about this side of things, as > >> clients "shouldn't" have to worry about them iff our error messages make > >> any sense. But, yes, adding such predicates would be a big help. > >> > >> They don't actually have to be part of svn::error, I'd make them > >> namespace-scope functions, e.g.: > >> > >> bool svn::error_is_eexist(const svn::error& e) noexcept; > >> > >> > >> the point being that the svn::error object serves as both an exception > >> type and a detailed error description (and that's the reason for > >> deriving svn::cancelled from svn::error). > > I don't disagree with adding such predicates, but they aren't my point. > > What I was trying to say is, doesn't the standard C++ exception > > hierarchy have some std::* exception class for, say, IO errors? In > > which case, C++ consumers might be surprised that an svn::error object > > with apr_err==EEXIST isn't caught by their 'catch' clauses for std::* IO > > errors? > > Not so much. Or at least not as detailed as you'd think: > > https://en.cppreference.com/w/cpp/error/exception
Don't forget the system error stuff introduced in c++11: https://en.cppreference.com/w/cpp/header/system_error Cheers, -- James GPG Key: 4096R/91BF BF4D 6956 BD5D F7B7 2D23 DFE6 91AE 331B A3DB
