Re: [boost] cstring_view

On May 13, 2022, at 3:19 PM, Peter Dimov via Boost wrote:

Marshall Clow wrote:

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On May 13, 2022, at 12:29 PM, Rainer Deyke via Boost wrote:

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On 13.05.22 20:39, Marshall Clow via Boost wrote:

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On May 13, 2022, at 11:18 AM, Peter Dimov via Boost

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In what scenarios will it not give you a null-terminated string? char arr[6] = “hello"; cstring_view csv(arr); assert(strlen(csv.data())) == 5); arr[5] = ‘!’; assert(strlen(csv.data())) == 5); // boom — Marshall PS. It promises to give you a null-terminated string, but has no way to actually guarantee that.

That's an issue with views in general, not just cstring_view.

std::string s = "hello"; string_view sv = s; assert(sv.size() == 5); s += "!"; assert(sv.size() == 5); // boom

I don’t see the problem here (and when I run the code I get no error - after adding the missing ’std::').

No assertion failure; no undefined behavior (unlike the cstring_view example)

Only because "hello!" fits into the small buffer, I suspect. If `s` reallocates, `sv` would be left dangling.

Agreed. But even if the string *did* reallocate, the call "assert(sv.size() == 5)” is still valid and well defined. In the cstring_view example I wrote, there are no allocations (it’s a static buffer), and the call exhibits undefined behavior (as well as the assertion failure). The whole point of cstring_view is “I have a sequence of N characters here, and I *swear* that then n+1st one is a NUL” — Marshall P. S. Std::string has the same behavior (which I really dislike), but at least it owns the storage, so it can enforce the presence of the NUL.