Resolves#171362
- Implement proposed resolution
- Refactor `operator==` code to be more in line with the standard as the
current way was making an explicit `bool()` conversion in the `x.meow()
== y.meow()` cases
- Add test cases
- Update issues paper
---------
Co-authored-by: A. Jiang <de34@live.cn>
Reverts 45a65bb48b.
Currently, there is no consensus among LWG and standard library
maintainers that P3798R1 should be applied as a Defect Report. So it is
better to revert the paper application for now and then reapply it as an
addition in C++29 when C++29 mode is ready.
We don't actually need to evaluate anything as lazily as `_Lazy` does or
we can achieve the same amount of laziness in other ways, so we can get
rid of it. This was required previously in some places due to a Clang
bug, which has been resolved and implemented by all compilers we
support.
The C++26 constraint added to operator==(const expected& x, const T2& v)
by P3379R0 evaluates *x == v as part of constraint satisfaction. When
ADL on a comparison reaches this hidden friend through a type whose
associated namespaces include std::expected -- for example std::pair<T,
std::expected<U, V>> -- the constraint check ends up considering the
same overload again with the original type as T2, producing a
"satisfaction of constraint depends on itself" error.
Parameterize the expected operand with an extra template parameter
constrained to be the same type as the enclosing expected's value type.
This is observationally equivalent but makes template argument deduction
fail for non-expected operands before the constraint is evaluated, so
the recursion never starts.
Fixes#160431
rdar://178226313
Assisted-by: Claude
This patch introduces `_LIBCPP_{BEGIN/END}_EXPLICIT_ABI_ANNOTATIONS` and
marks everything within an
`_LIBCPP_{BEGIN,END}_UNVERSIONED_NAMESPACE_STD` (and any derivatives
like `_LIBCPP_{BEGIN,END}_NAMESPACE_STD`) implicitly by default. This
allows us to drop `_LIBCPP_HIDE_FROM_ABI` in most of the code base,
except for functions which shouldn't be `_LIBCPP_HIDE_FROM_ABI`.
This patch doesn't remove any `_LIBCPP_HIDE_FROM_ABI`s, since we have
over 13k of them in the code base. Actually dropping them will happen
over some time to avoid too many merge conflicts.
The Trivial Relocation feature has been removed from the C++26 working
draft. Based on discussions in Kona, it is unlikely that the
"replaceable" type concept will come back in the C++29 time frame.
Since we don't have a use for the type trait in the library at the
moment, remove the code associated to it. If we end up needing something
like it in the future, we can always add it back.
This reverts commit c861fe8a71.
Unfortunately, this use of hidden visibility attributes causes
user-defined specializations of standard-library types to also be marked
hidden by default, which is incorrect. See discussion thread on #131156.
...and also reverts the follow-up commits:
Revert "[libc++] Add explicit ABI annotations to functions from the block runtime declared in <__functional/function.h> (#140592)"
This reverts commit 3e4c9dc299.
Revert "[libc++] Make ABI annotations explicit for windows-specific code (#140507)"
This reverts commit f73287e623.
Revert "[libc++][NFC] Replace a few "namespace std" with the correct macro (#140510)"
This reverts commit 1d411f27c7.
This patch introduces `_LIBCPP_{BEGIN,END}_EXPLICIT_ABI_ANNOTATIONS`,
which allow us to have implicit annotations for most functions, and just
where it's not "hide_from_abi everything" we add explicit annotations.
This allows us to drop the `_LIBCPP_HIDE_FROM_ABI` macro from most
functions in libc++.
That type trait represents whether move-assigning an object is
equivalent to destroying it and then move-constructing a new one from
the same argument. This will be useful in a few places where we may want
to destroy + construct instead of doing an assignment, in particular
when implementing some container operations in terms of relocation.
This is effectively adding a library emulation of P2786R12's
is_replaceable trait, similarly to what we do for trivial relocation.
Eventually, we can replace this library emulation by the real
compiler-backed trait.
This is building towards #129328.
Currently, libc++ incorrectly rejects heterogeneous comparison of
`unexpected`, because the `operator==` is only a hidden friend of
`unexpected<_Err>` but not of `unexpected<_Err2>`. We need to call the
`error()` member function on `__y`.
Fixes#115326
Currently, the library-internal feature test macros are only defined if
the feature is not available, and always have the prefix
`_LIBCPP_HAS_NO_`. This patch changes that, so that they are always
defined and have the prefix `_LIBCPP_HAS_` instead. This changes the
canonical use of these macros to `#if _LIBCPP_HAS_FEATURE`, which means
that using an undefined macro (e.g. due to a missing include) is
diagnosed now. While this is rather unlikely currently, a similar change
in `<__configuration/availability.h>` caught a few bugs. This also
improves readability, since it removes the double-negation of `#ifndef
_LIBCPP_HAS_NO_FEATURE`.
The current patch only touches the macros defined in `<__config>`. If
people are happy with this approach, I'll make a follow-up PR to also
change the macros defined in `<__config_site>`.
This patch adds a large number of missing includes in the libc++ headers
and the test suite. Those were found as part of the effort to move
towards a mostly monolithic top-level std module.
This re-formats a few headers that had become out-of-sync with respect
to formatting since we ran clang-format on the whole codebase. There's
surprisingly few instances of it.
Instead of using **this in error messages for std::expected monadic
operations, use value(). As shown in LWG3969, **this can trigger
unintended ADL and while it's only an error message, we might as
well be ADL-correct there too.
Co-authored-by: Louis Dionne <ldionne.2@gmail.com>
fixes#92676
So right now clang does not like
```
std::expected<std::any, int> e1;
auto e2 = e1;
```
So basically when clang tries to do overload resolution of `auto e2 =
e1;`
It finds
```
expected(const expected&); // 1. This is OK
expected(const expected<_Up, _OtherErr>&) requires __can_convert; // 2. This needs to check its constraints
```
Then in `__can_convert`, one of the check is
```
_Not<is_constructible<_Tp, expected<_Up, _OtherErr>&>>
```
which is checking
```
is_constructible<std::any, expected<_Up, _OtherErr>&>
```
Then it looks at `std::any`'s constructor
```
template < class _ValueType,
class _Tp = decay_t<_ValueType>,
class = enable_if_t< !is_same<_Tp, any>::value && !__is_inplace_type<_ValueType>::value &&
is_copy_constructible<_Tp>::value> >
any(_ValueType&& __value);
```
In the above, `is_copy_constructible<_Tp>` expands to
```
is_copy_constructible<std::expected<std::any, int>>
```
And the above goes back to the original thing we asked : copy the
`std::expected`, which goes to the overload resolution again.
```
expected(const expected&);
expected(const expected<_Up, _OtherErr>&) requires __can_convert;
```
So the second overload results in a logical cycle.
I am not a language lawyer. We could argue that clang should give up on
the second overload which has logical cycle, as the first overload is a
perfect match.
Anyway, the fix in this patch tries to short-circuiting the second
overload's constraint check: that is, if the argument matches exact same
`expected<T, E>`, we give up immediately and let the copy constructor to
deal with it
In essence, this header has always been related to configuration of
the library but we didn't want to put it inside <__config> due to
complexity reasons. Now that we have sub-headers in <__config>, we
can move <__availability> to it and stop including it everywhere since
we already obtain the required macros via <__config>.
This patch uses our availability machinery to allow defining a key
function for bad_function_call and bad_expected_access at all times but
only rely on it when we can. This prevents compilers from complaining
about weak vtables and reduces code bloat and the amount of work done by
the dynamic linker.
rdar://111917845
This was actually already implemented in the initial version of
std::expected, but this patch adds test coverage and makes it more
explicit that we intend to make these functions noexcept.
These headers have become very small by using compiler builtins, often
containing only two declarations. This merges these headers, since
there doesn't seem to be much of a benefit keeping them separate.
Specifically, `is_{,_nothrow,_trivially}{assignable,constructible}` are
kept and the `copy`, `move` and `default` versions of these type traits
are moved in to the respective headers.
Currently std::expected can have some padding bytes in its tail due to
[[no_unique_address]]. Those padding bytes can be used by other objects.
For example, in the current implementation:
sizeof(std::expected<std::optional<int>, bool>) ==
sizeof(std::expected<std::expected<std::optional<int>, bool>, bool>)
As a result, the data layout of an
std::expected<std::expected<std::optional<int>, bool>, bool>
can look like this:
+-- optional "has value" flag
| +--padding
/---int---\ | |
00 00 00 00 01 00 00 00
| |
| +- "outer" expected "has value" flag
|
+- expected "has value" flag
This is problematic because `emplace()`ing the "inner" expected can not
only overwrite the "inner" expected "has value" flag (issue #68552) but
also the tail padding where other objects might live.
This patch fixes the problem by ensuring that std::expected has no tail
padding, which is achieved by conditional usage of [[no_unique_address]]
based on the tail padding that this would create.
This is an ABI breaking change because the following property changes:
sizeof(std::expected<std::optional<int>, bool>) <
sizeof(std::expected<std::expected<std::optional<int>, bool>, bool>)
Before the change, this relation didn't hold. After the change, the relation
does hold, which means that the size of std::expected in these cases increases
after this patch. The data layout will change in the following cases where
tail padding can be reused by other objects:
class foo : std::expected<std::optional<int>, bool> {
bool b;
};
or using [[no_unique_address]]:
struct foo {
[[no_unique_address]] std::expected<std::optional<int>, bool> e;
bool b;
};
The vendor communication is handled in #70820.
Fixes: #70494
Co-authored-by: philnik777 <nikolasklauser@berlin.de>
Co-authored-by: Louis Dionne <ldionne.2@gmail.com>
This patch runs clang-format on all of libcxx/include and libcxx/src, in
accordance with the RFC discussed at [1]. Follow-up patches will format
the benchmarks, the test suite and remaining parts of the code. I'm
splitting this one into its own patch so the diff is a bit easier to
review.
This patch was generated with:
find libcxx/include libcxx/src -type f \
| grep -v 'module.modulemap.in' \
| grep -v 'CMakeLists.txt' \
| grep -v 'README.txt' \
| grep -v 'libcxx.imp' \
| grep -v '__config_site.in' \
| xargs clang-format -i
A Git merge driver is available in libcxx/utils/clang-format-merge-driver.sh
to help resolve merge and rebase issues across these formatting changes.
[1]: https://discourse.llvm.org/t/rfc-clang-formatting-all-of-libc-once-and-for-all
The calls to std::construct_at might overwrite the previously set
__has_value_ flag in the case where the flag is overlapping with
the actual value or error being stored (since we use [[no_unique_address]]).
To fix this issue, this patch ensures that we initialize the
__has_value_ flag after we call std::construct_at.
Fixes#68552
POSIX allows certain macros to exist with generic names (i.e. refresh(), move(), and erase()) to exist in `curses.h` which conflict with functions found in std::filesystem, among others. This patch undefs the macros in question and adds them to LIBCPP_PUSH_MACROS and LIBCPP_POP_MACROS.
Reviewed By: #libc, philnik, ldionne
Differential Revision: https://reviews.llvm.org/D147356
Replace most uses of `_LIBCPP_ASSERT` with
`_LIBCPP_ASSERT_UNCATEGORIZED`.
This is done as a prerequisite to introducing hardened mode to libc++.
The idea is to make enabling assertions an opt-in with (somewhat)
fine-grained controls over which categories of assertions are enabled.
The vast majority of assertions are currently uncategorized; the new
macro will allow turning on `_LIBCPP_ASSERT` (the underlying mechanism
for all kinds of assertions) without enabling all the uncategorized
assertions (in the future; this patch preserves the current behavior).
Differential Revision: https://reviews.llvm.org/D153816
This reverts commit ebc111b08b.
Sorry, I forgot to append Phabricator reversion when land D140911, I try to revert this change and reland.
Reviewed By: #libc, ldionne, EricWF
Differential Revision: https://reviews.llvm.org/D150793
We already have a clang-tidy check for making sure that `_LIBCPP_HIDE_FROM_ABI` is on free functions. This patch extends this to class members. The places where we don't check for `_LIBCPP_HIDE_FROM_ABI` are classes for which we have an instantiation in the library.
Reviewed By: ldionne, Mordante, #libc
Spies: jplehr, mikhail.ramalho, sstefan1, libcxx-commits, krytarowski, miyuki, smeenai
Differential Revision: https://reviews.llvm.org/D142332
We changed the `abort` calls when trying to throw exceptions in `-fno-exceptions` mode to `__verbose_abort` calls, which removes the dependency in most files.
Reviewed By: ldionne, #libc
Spies: dim, emaste, mikhail.ramalho, smeenai, libcxx-commits
Differential Revision: https://reviews.llvm.org/D146076
This results in proper error messages instead of just an abort.
Reviewed By: ldionne, Mordante, #libc
Spies: #libc_vendors, smeenai, libcxx-commits
Differential Revision: https://reviews.llvm.org/D141222
Uses an absolute path to the selected binary.
Updates the formatting of two files to match clang-format-16 style.
Depends on D144126
Reviewed By: #libc, philnik
Differential Revision: https://reviews.llvm.org/D144132
Other macros that disable parts of the library are named `_LIBCPP_HAS_NO_WHATEVER`.
Reviewed By: ldionne, Mordante, #libc
Spies: libcxx-commits, smeenai
Differential Revision: https://reviews.llvm.org/D143163
