In 0547e573c555, I introduced backdeployment testing on macOS using Github-provided builders. This was done by basically building libc++ on a slightly older macOS (like macOS 13) and then running against the system library on that machine. However, that created a dependency that libc++ must keep working on macOS 13, which doesn't support the latest-released Xcode. This patch solves that problem by moving the deployment testing to a newer version of macOS which supports the latest-released version of Xcode. Sadly, that also reduces the backdeployment coverage we have since we're not actually testing on older OSes, but is necessary to satisfy the documented libc++ support policy. In the future, we could improve the situation by providing a Lit configuration that allows compiling (but not running) all the tests, building the tests on a supported macOS, and then shipping those tests on an older backdeployment target in order to run them against the system library. Since that requires significant engineering, this isn't done at this time.
Without this patch `basic_string` cannot be properly resized to be `max_size()` elements in size, even if an allocation is successful. `__grow_by` allocates one less element than required, resulting in an out-of-bounds access. At the same time, `max_size()` has an off-by-one error, since there has to be space to store the null terminator, which is currently ignored.
This patch removes many annotations that are not relevant anymore since we don't support or test back-deploying to macOS < 10.13. It also cleans up raw usage of target triples to identify versions of dylibs shipped on prior versions of macOS, and uses the target-agnostic Lit features instead. Finally, it reorders both the Lit backdeployment features and the corresponding availability macros in the library in a way that makes more sense, and reformulates the Lit backdeployment features in terms of when a version of LLVM was introduced instead of encoding the system versions on which it hasn't been introduced yet. Although one can be derived from the other, encoding the negative form is extremely error-prone. Fixes #80901
We were not making any distinction between e.g. the "Apple-flavored" libc++ built from trunk and the system-provided standard library on Apple platforms. For example, any test that would be XFAILed on a back-deployment target would unexpectedly pass when run on that deployment target against the tip of trunk Apple-flavored libc++. In reality, that test would be expected to pass because we're running against the latest libc++, even if it is Apple-flavored. To solve this issue, we introduce a new feature that describes whether the Standard Library in use is the one provided by the system by default, and that notion is different from the underlying standard library flavor. We also refactor the existing Lit features to make a distinction between availability markup and the library we're running against at runtime, which otherwise limit the flexibility of what we can express in the test suite. Finally, we refactor some of the back-deployment versions that were incorrect (such as thinking that LLVM 10 was introduced in macOS 11, when in reality macOS 11 was synced with LLVM 11). Fixes #82107
Unconditionally change std::string's alignment to 8. This change saves memory by providing the allocator more freedom to allocate the most efficient size class by dropping the alignment requirements for std::string's pointer from 16 to 8. This changes the output of std::string::max_size, which makes it ABI breaking. That said, the discussion concluded that we don't care about this ABI break. and would like this change enabled universally. The ABI break isn't one of layout or "class size", but rather the value of "max_size()" changes, which in turn changes whether `std::bad_alloc` or `std::length_error` is thrown for large allocations. This change is the child of PR #68807, which enabled the change behind an ABI flag.
While doing this, I also found a few tests that were either clearly incorrect (e.g. testing the wrong function) or that lacked basic test coverage like testing std::string itself (e.g. the test was only checking std::basic_string with a custom allocator). In these cases, I did a few conservative drive-by changes. Differential Revision: https://reviews.llvm.org/D140550 Co-authored-by: Brendan Emery <brendan.emery@esrlabs.com>
This applies clang-format to the std::string unit tests in preparation for landing https://reviews.llvm.org/D140550. Differential Revision: https://reviews.llvm.org/D140612
This has been done using the following command
find libcxx/test -type f -exec perl -pi -e 's|^([^/]+?)((?<!::)size_t)|\1std::\2|' \{} \;
And manually removed some false positives in std/depr/depr.c.headers.
The `std` module doesn't export `::size_t`, this is a preparation for that module.
Reviewed By: ldionne, #libc, EricWF, philnik
Differential Revision: https://reviews.llvm.org/D146088
Reviewed By: ldionne, #libc Spies: vitalybuka, paulkirth, libcxx-commits, mgorny Differential Revision: https://reviews.llvm.org/D132790