| Issue |
91634
|
| Summary |
std::string_view::substr triggers unnecessary ctor safety checks in libc++ safe mode
|
| Labels |
libc++
|
| Assignees |
|
| Reporter |
davidben
|
std::string_view checks that the input length is less than `PTRDIFF_MAX`, which is useful for caching accidental negative numbers getting in there.
But the cost is that the various methods of `string_view` trigger this check too, because the compiler doesn't know that `sv.size() <= PTRDIFF_MAX`. See this godbolt:
https://godbolt.org/z/zsG4rbTdb
We could fix this with some assumes, but Clang cannot do this analysis anyway (see #91619). So I think probably the simplest option is to add a private ctor, `string_view(ptr, len, __assume_valid)` and make the internal calls use that one.
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