7b4622514d
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
116 lines
3.5 KiB
C++
116 lines
3.5 KiB
C++
// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___NUMERIC_SATURATION_ARITHMETIC_H
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#define _LIBCPP___NUMERIC_SATURATION_ARITHMETIC_H
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#include <__concepts/arithmetic.h>
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#include <__config>
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#include <__utility/cmp.h>
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#include <limits>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_PUSH_MACROS
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#include <__undef_macros>
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_LIBCPP_BEGIN_NAMESPACE_STD
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#if _LIBCPP_STD_VER >= 26
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template <__libcpp_integer _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Tp add_sat(_Tp __x, _Tp __y) noexcept {
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if (_Tp __sum; !__builtin_add_overflow(__x, __y, &__sum))
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return __sum;
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// Handle overflow
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if constexpr (__libcpp_unsigned_integer<_Tp>) {
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return std::numeric_limits<_Tp>::max();
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} else {
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// Signed addition overflow
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if (__x > 0)
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// Overflows if (x > 0 && y > 0)
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return std::numeric_limits<_Tp>::max();
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else
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// Overflows if (x < 0 && y < 0)
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return std::numeric_limits<_Tp>::min();
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}
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}
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template <__libcpp_integer _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Tp sub_sat(_Tp __x, _Tp __y) noexcept {
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if (_Tp __sub; !__builtin_sub_overflow(__x, __y, &__sub))
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return __sub;
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// Handle overflow
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if constexpr (__libcpp_unsigned_integer<_Tp>) {
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// Overflows if (x < y)
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return std::numeric_limits<_Tp>::min();
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} else {
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// Signed subtration overflow
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if (__x >= 0)
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// Overflows if (x >= 0 && y < 0)
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return std::numeric_limits<_Tp>::max();
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else
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// Overflows if (x < 0 && y > 0)
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return std::numeric_limits<_Tp>::min();
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}
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}
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template <__libcpp_integer _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Tp mul_sat(_Tp __x, _Tp __y) noexcept {
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if (_Tp __mul; !__builtin_mul_overflow(__x, __y, &__mul))
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return __mul;
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// Handle overflow
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if constexpr (__libcpp_unsigned_integer<_Tp>) {
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return std::numeric_limits<_Tp>::max();
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} else {
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// Signed multiplication overflow
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if ((__x > 0 && __y > 0) || (__x < 0 && __y < 0))
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return std::numeric_limits<_Tp>::max();
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// Overflows if (x < 0 && y > 0) || (x > 0 && y < 0)
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return std::numeric_limits<_Tp>::min();
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}
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}
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template <__libcpp_integer _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Tp div_sat(_Tp __x, _Tp __y) noexcept {
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_LIBCPP_ASSERT_UNCATEGORIZED(__y != 0, "Division by 0 is undefined");
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if constexpr (__libcpp_unsigned_integer<_Tp>) {
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return __x / __y;
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} else {
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// Handle signed division overflow
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if (__x == std::numeric_limits<_Tp>::min() && __y == _Tp{-1})
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return std::numeric_limits<_Tp>::max();
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return __x / __y;
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}
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}
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template <__libcpp_integer _Rp, __libcpp_integer _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Rp saturate_cast(_Tp __x) noexcept {
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// Saturation is impossible edge case when ((min _Rp) < (min _Tp) && (max _Rp) > (max _Tp)) and it is expected to be
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// optimized out by the compiler.
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// Handle overflow
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if (std::cmp_less(__x, std::numeric_limits<_Rp>::min()))
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return std::numeric_limits<_Rp>::min();
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if (std::cmp_greater(__x, std::numeric_limits<_Rp>::max()))
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return std::numeric_limits<_Rp>::max();
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// No overflow
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return static_cast<_Rp>(__x);
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}
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#endif // _LIBCPP_STD_VER >= 26
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_LIBCPP_END_NAMESPACE_STD
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_LIBCPP_POP_MACROS
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#endif // _LIBCPP___NUMERIC_SATURATION_ARITHMETIC_H
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