Instead of writing something like `XFAIL: use_system_cxx_lib && target=...`
to XFAIL back-deployment tests, introduce named Lit features like
`availability-shared_mutex-missing` to represent those. This makes the
XFAIL annotations leaner, and solves the problem of XFAIL comments
potentially getting out of sync. This would also make it easier for
another vendor to add their own annotations to the test suite by simply
changing how the feature is defined for their OS releases, instead
of having to modify hundreds of tests to add repetitive annotations.
This doesn't touch *all* annotations -- only annotations that were widely
duplicated are given named features (e.g. when filesystem or shared_mutex
were introduced). I still think it probably doesn't make sense to have a
named feature for every single fix we make to the dylib.
This is in essence a revert of 2659663, but since then the test suite
has changed significantly. Back when I did 2659663, the configuration
files we have for the test suite right now were being bootstrapped and
it wasn't clear how to provide these features for back-deployment in
that context. Since then, we have a streamlined way of defining these
features in `features.py` and that doesn't impact the ability for a
configuration file to stay minimal.
The original motivation for this change was that I am about to propose
a change that would touch essentially all XFAIL annotations for back-deployment
in the test suite, and this greatly reduces the number of lines changed
by that upcoming change, in addition to making the test suite generally
better.
Differential Revision: https://reviews.llvm.org/D146359
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
Don't forward to `min_element` for small types that are trivially copyable, and instead use a naive loop that keeps track of the smallest element (as opposed to an iterator to the smallest element). This allows the compiler to vectorize the loop in some cases.
Reviewed By: #libc, ldionne
Spies: ldionne, libcxx-commits
Differential Revision: https://reviews.llvm.org/D143596
https://wg21.link/LWG2444 updated the comparison complexity of
std:sort_heap to be at most 2N log (N) where N == last - first. In the
current implementation, we invoke __pop_heap exactly N-1 times. In each
call to __pop_heap, we first go down the heap from first to possibly
last in the function __floyd_sift_down. Then, we possibly go back up in
the function __sift_up.
In the function __floyd_sift_down, there is loop in which one comparison
is made in each iteration. The loop runs till __child becomes greater
than (__len - 2) / 2. __child starts at 0 and it is at least set to 2 *
__child + 1 on each iteration. Thus, after k iterations, __child will
be at least 2^k - 1. After log(N) iterations, __child >= 2^(log(N)) -
1 = N - 1 > (__len - 2) / 2. This means that the while loop in the
function __floyd_sift_down would perform at most log(N) comparisons on
each invocation.
In the function __sift_up, there is one comparison made that will almost
always occur. After that there is a do-while loop. The comparison
function is invoked once in each iteration. In the worst case, the loop
will run till __len goes down to zero. It can start from (N-3)/2. In
each iteration, __len goes down to (__len-1) / 2. After k iterations,
__len will be at most (N - 2^(k+1) -1) / 2^(k+1). Thus, __len will
become when (N-2^(k+1)-1) < 2^(k+1) i.e. N < 2^(k+2) + 1. This means
at most log(N) - 1 iterations for the loop. So in total at most log(N)
comparison will be performed in __sift_up.
So overall for each iteration of the loop in __pop_heap, there will at
most 2 log(N) comparisons. So, the total number of comparisons is
at most 2 N log(N).
We also updated the test sort.heap/complexity.pass.cpp to test for the
number of operations.
Differential Revision: https://reviews.llvm.org/D144538
The implementation makes use of the freedom added by LWG 3410. We have
two variants of this algorithm:
* a fast path for random access iterators: This fast path computes the
maximum number of loop iterations up-front and does not compare the
iterators against their limits on every loop iteration.
* A basic implementation for all other iterators: This implementation
compares the iterators against their limits in every loop iteration.
However, it still takes advantage of the freedom added by LWG 3410 to
avoid unnecessary additional iterator comparisons, as originally
specified by P1614R2.
https://godbolt.org/z/7xbMEen5e shows the benefit of the fast path:
The hot loop generated of `lexicographical_compare_three_way3` is
more tight than for `lexicographical_compare_three_way1`. The added
benchmark illustrates how this leads to a 30% - 50% performance
improvement on integer vectors.
Implements part of P1614R2 "The Mothership has Landed"
Fixes LWG 3410 and LWG 3350
Differential Revision: https://reviews.llvm.org/D131395
Per our policy, the latest released AppleClang has been 14 for a while,
so libc++ is removing support for AppleClang 13. Our CI bots have been
moved to AppleClang 14 a few weeks ago.
Differential Revision: https://reviews.llvm.org/D138685
This mirrors what we have done in the classic algorithms
Reviewed By: ldionne, #libc
Spies: libcxx-commits
Differential Revision: https://reviews.llvm.org/D137186
compressed_pair is widely used in the library, but most of the uses don't use the tuple parts. To avoid including <tuple> everywhere, use the forward declaration instead in compressed_pair.h
Reviewed By: ldionne, #libc
Spies: libcxx-commits
Differential Revision: https://reviews.llvm.org/D133331
Adding `[[nodiscard]]` to functions is a conforming extension and done extensively in the MSVC STL.
Reviewed By: ldionne, EricWF, #libc
Spies: #libc_vendors, cjdb, mgrang, jloser, libcxx-commits
Differential Revision: https://reviews.llvm.org/D128267
When we ship LLVM 16, <ranges> won't be considered experimental anymore.
We might as well do this sooner rather than later.
Differential Revision: https://reviews.llvm.org/D132151
The return type was specified incorrectly for proxy iterators that
define `reference` to be a class that implicitly converts to
`value_type`. `__iter_move` would end up returning an object of type
`reference` which would then implicitly convert to `value_type`; thus,
the function will return a `value_type&&` rvalue reference to the local
temporary.
Differential Revision: https://reviews.llvm.org/D130197
In particular remove the ability to expel incomplete features from the
library at configure-time, since this can now be done through the
_LIBCPP_ENABLE_EXPERIMENTAL macro.
Also, never provide symbols related to incomplete features inside the
dylib, instead provide them in c++experimental.a (this changes the
symbols list, but not for any configuration that should have shipped).
Differential Revision: https://reviews.llvm.org/D128928
- create the headers (but not include them from `<algorithm>`);
- define the niebloid and its member functions with the right signatures
(as no-ops);
- make sure all the right headers are included that are required by each
algorithm's signature;
- update `CMakeLists.txt` and the module map;
- create the test files with the appropriate synopses.
The synopsis in `<algorithm>` is deliberately not updated because that
could be taken as a readiness signal. The new headers aren't included
from `<algorithm>` for the same reason.
Differential Revision: https://reviews.llvm.org/D129549
implement `std::ranges::set_intersection` by reusing the classic `std::set_intersenction`
added unit tests
Differential Revision: https://reviews.llvm.org/D129233
It is meant to be used in ranges algorithm tests.
It is much simplified version of C++23's tuple + zip_view.
Using std::swap would cause compilation failure and using `std::move` would not create the correct rvalue proxy which would result in copies.
Differential Revision: https://reviews.llvm.org/D129099
Display 'static_assert failed: message' instead of
'static_assert failed "message"' to be consistent
with other implementations and be slightly more
readable.
Reviewed By: #libc, aaron.ballman, philnik, Mordante
Differential Revision: https://reviews.llvm.org/D128844
The debug mode has been broken pretty much ever since it was shipped
because it was possible to enable the debug mode in user code without
actually enabling it in the dylib, leading to ODR violations that
caused various kinds of failures.
This commit makes the debug mode a knob that is configured when
building the library and which can't be changed afterwards. This is
less flexible for users, however it will actually work as intended
and it will allow us, in the future, to add various kinds of checks
that do not assume the same ABI as the normal library. Furthermore,
this will make the debug mode more robust, which means that vendors
might be more tempted to support it properly, which hasn't been the
case with the current debug mode.
This patch shouldn't break any user code, except folks who are building
against a library that doesn't have the debug mode enabled and who try
to enable the debug mode in their code. Such users will get a compile-time
error explaining that this configuration isn't supported anymore.
In the future, we should further increase the granularity of the debug
mode checks so that we can cherry-pick which checks to enable, like we
do for unspecified behavior randomization.
Differential Revision: https://reviews.llvm.org/D122941
