Implements [P3044R2](https://wg21.link/P3044R2) Note: `substr.pass.cpp` is refactored to accommodate the test of `basic_string_view`'s `subview` which is an alias of `substr` without changing the test cases. Closes #148140 # References - https://github.com/cplusplus/draft/pull/7975 - https://wg21.link/string.substr - https://wg21.link/string.view.ops --------- Co-authored-by: Hristo Hristov <zingam@outlook.com> Co-authored-by: Nikolas Klauser <nikolasklauser@berlin.de>
We've built up quite a few links directly to github within the code base. We should instead use `llvm.org/PR<issue-number>` to link to bugs, since that is resilient to the bug tracker changing in the future. This is especially relevant for tests linking to bugs, since they will probably be there for decades to come. A nice side effect is that these links are significantly shorter than the GH links, making them much less of an eyesore. This patch also replaces a few links that linked to the old bugzilla instance on llvm.org.
When assertions are enabled it is impossible to construct a `string_view` which contains a null pointer and a non-zero size, so assertions where we check for that on an already constructed `string_view` are unreachable.
Previously, the segmented iterator optimization for `std::for_each` was restricted to C++23 and later due to its dependency on `__movable_box`, which is not available in earlier standards. This patch eliminates that restriction, enabling consistent optimizations starting from C++11. By backporting this enhancement, we improve performance across older standards and create opportunities to extend similar optimizations to other algorithms by forwarding their calls to `std::for_each`.
Requirements on character-like types are updated unconditionally, because `basic_string` does requires the default-constructibility. It might be possible to make `basic_string_view` support classes with non-public trivial default constructor, but this doesn't seem sensible. libcxxabi's `ItaniumDemangle.h` is also updated to avoid deprecated features.
This is technically not necessary in most cases to prevent issues with ADL, but let's be consistent. This allows us to remove the libcpp-qualify-declval clang-tidy check, which is now enforced by the robust-against-adl clang-tidy check.
This patch implements the forwarding to frozen C++03 headers as discussed in https://discourse.llvm.org/t/rfc-freezing-c-03-headers-in-libc. In the RFC, we initially proposed selecting the right headers from the Clang driver, however consensus seemed to steer towards handling this in the library itself. This patch implements that direction. At a high level, the changes basically amount to making each public header look like this: ``` // inside <vector> #ifdef _LIBCPP_CXX03_LANG # include <__cxx03/vector> #else // normal <vector> content #endif ``` In most cases, public headers are simple umbrella headers so there isn't much code in the #else branch. In other cases, the #else branch contains the actual implementation of the header.
Including The frozen C++03 headers results in a lot of formatting changes in the main headers, so this splits these changes into a separate commit instead. This is part of https://discourse.llvm.org/t/rfc-freezing-c-03-headers-in-libc.