llvm-project/libcxx/include/__algorithm/ranges_max_element.h
Louis Dionne 7b4622514d
[libc++] Fix missing and incorrect push/pop macros (#79204)
We recently noticed that the unwrap_iter.h file was pushing macros, but
it was pushing them again instead of popping them at the end of the
file. This led to libc++ basically swallowing any custom definition of
these macros in user code:

    #define min HELLO
    #include <algorithm>
    // min is not HELLO anymore, it's not defined

While investigating this issue, I noticed that our push/pop pragmas were
actually entirely wrong too. Indeed, instead of pushing macros like
`move`, we'd push `move(int, int)` in the pragma, which is not a valid
macro name. As a result, we would not actually push macros like `move`
-- instead we'd simply undefine them. This led to the following code not
working:

    #define move HELLO
    #include <algorithm>
    // move is not HELLO anymore

Fixing the pragma push/pop incantations led to a cascade of issues
because we use identifiers like `move` in a large number of places, and
all of these headers would now need to do the push/pop dance.

This patch fixes all these issues. First, it adds a check that we don't
swallow important names like min, max, move or refresh as explained
above. This is done by augmenting the existing
system_reserved_names.gen.py test to also check that the macros are what
we expect after including each header.

Second, it fixes the push/pop pragmas to work properly and adds missing
pragmas to all the files I could detect a failure in via the newly added
test.

rdar://121365472
2024-01-25 15:48:46 -05:00

70 lines
2.5 KiB
C++

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___ALGORITHM_RANGES_MAX_ELEMENT_H
#define _LIBCPP___ALGORITHM_RANGES_MAX_ELEMENT_H
#include <__algorithm/ranges_min_element.h>
#include <__config>
#include <__functional/identity.h>
#include <__functional/invoke.h>
#include <__functional/ranges_operations.h>
#include <__iterator/concepts.h>
#include <__iterator/projected.h>
#include <__ranges/access.h>
#include <__ranges/concepts.h>
#include <__ranges/dangling.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_PUSH_MACROS
#include <__undef_macros>
#if _LIBCPP_STD_VER >= 20
_LIBCPP_BEGIN_NAMESPACE_STD
namespace ranges {
namespace __max_element {
struct __fn {
template <forward_iterator _Ip,
sentinel_for<_Ip> _Sp,
class _Proj = identity,
indirect_strict_weak_order<projected<_Ip, _Proj>> _Comp = ranges::less>
_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr _Ip
operator()(_Ip __first, _Sp __last, _Comp __comp = {}, _Proj __proj = {}) const {
auto __comp_lhs_rhs_swapped = [&](auto&& __lhs, auto&& __rhs) -> bool { return std::invoke(__comp, __rhs, __lhs); };
return ranges::__min_element_impl(__first, __last, __comp_lhs_rhs_swapped, __proj);
}
template <forward_range _Rp,
class _Proj = identity,
indirect_strict_weak_order<projected<iterator_t<_Rp>, _Proj>> _Comp = ranges::less>
_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr borrowed_iterator_t<_Rp>
operator()(_Rp&& __r, _Comp __comp = {}, _Proj __proj = {}) const {
auto __comp_lhs_rhs_swapped = [&](auto&& __lhs, auto&& __rhs) -> bool { return std::invoke(__comp, __rhs, __lhs); };
return ranges::__min_element_impl(ranges::begin(__r), ranges::end(__r), __comp_lhs_rhs_swapped, __proj);
}
};
} // namespace __max_element
inline namespace __cpo {
inline constexpr auto max_element = __max_element::__fn{};
} // namespace __cpo
} // namespace ranges
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP_STD_VER >= 20
_LIBCPP_POP_MACROS
#endif // _LIBCPP___ALGORITHM_RANGES_MAX_ELEMENT_H