Re: [boost] [string_ref] degree of conformance to standard proposal

On 12/22/2013 07:26 PM, Marshall Clow wrote:

On Dec 22, 2013, at 6:21 AM, Peter A. Bigot wrote:

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(Background: I need a string_view with features in N3762 that aren't in N3442 (viz., pos parameters to the string methods). I'm trying to determine how much effort I should put into a set of patches to update the Boost implementation to the latest draft proposal.)

The default constructor for Boost.string_ref produces an object which returns a null pointer from data(). N3442 and its successor N3762 both require the return value from data() to be non-null (http://isocpp.org/files/papers/N3762.html#h5o-5).

Yeah; I’ve spoken to Jeffrey (author of the proposal) and will be filing a defect report about that.

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GCC's libstdc++ folks solved this by adding a constexpr unit length string to serve as the base referenced object (http://gcc.gnu.org/ml/libstdc++/2013-11/msg00104.html). But for Boost I don't see how this can be changed without introducing a link dependency.

Right.

Not to mention that if you initialize a string_ref ( NULL, 0 )

To correct my previous comment, that constructor specifically disallows passing NULL; I believe the string_ref(char*) one disallows it implicitly. As I read N3762 there is no way to have a string_view reference something that isn't a valid (possibly zero-length) character sequence.

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Similarly, the standard proposal has settled on *string_view instead of *string_ref. Would Boost rename the library/class, or just introduce an alias?

I have that on my to-do list.

My thought is to rename the classes to match the standard, but keep the string_ref typedefs for compatibility. [ I’m open to other suggestions. ]

I will happily consider patches for the missing features. [ Though my opinion is that replicating the entire interface of std::string in string_[ref|view] is a mistake ]

https://github.com/boostorg/utility/pull/2 has the patches I've prepared, which are sufficient to meet my needs. At this time I don't propose to provide patches to fix the potential for null references and rename the class as both are messier than I want to tackle at this stage of my Boost experience. Peter