qtypes.cpp

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// Copyright (C) 2022 The Qt Company Ltd.
// Copyright (C) 2022 Intel Corporation.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
#include "qtypes.h"
 
#include <QtCore/qcompilerdetection.h>
#include <QtCore/qsystemdetection.h>
#include <QtCore/qprocessordetection.h>
 
#include <climits>
#include <limits>
#include <type_traits>
 
QT_BEGIN_NAMESPACE
 
// Statically check assumptions about the environment we're running
// in. The idea here is to error or warn if otherwise implicit Qt
// assumptions are not fulfilled on new hardware or compilers
// (if this list becomes too long, consider factoring into a separate file)
static_assert(UCHAR_MAX == 255, "Qt assumes that char is 8 bits");
static_assert(sizeof(int) == 4, "Qt assumes that int is 32 bits");
static_assert(QT_POINTER_SIZE == sizeof(void *), "QT_POINTER_SIZE defined incorrectly");
static_assert(sizeof(float) == 4, "Qt assumes that float is 32 bits");
static_assert(sizeof(char16_t) == 2, "Qt assumes that char16_t is 16 bits");
static_assert(sizeof(char32_t) == 4, "Qt assumes that char32_t is 32 bits");
#if defined(Q_OS_WIN)
static_assert(sizeof(wchar_t) == sizeof(char16_t));
#endif
static_assert(std::numeric_limits<int>::radix == 2,
                  "Qt assumes binary integers");
static_assert((std::numeric_limits<int>::max() + std::numeric_limits<int>::lowest()) == -1,
                  "Qt assumes two's complement integers");
static_assert(sizeof(wchar_t) == sizeof(char32_t) || sizeof(wchar_t) == sizeof(char16_t),
              "Qt assumes wchar_t is compatible with either char32_t or char16_t");
 
// While we'd like to check for __STDC_IEC_559__, as per ISO/IEC 9899:2011
// Annex F (C11, normative for C++11), there are a few corner cases regarding
// denormals where GHS compiler is relying hardware behavior that is not IEC
// 559 compliant. So split the check in several subchecks.
 
// On GHS the compiler reports std::numeric_limits<float>::is_iec559 as false.
// This is all right according to our needs.
#if !defined(Q_CC_GHS)
static_assert(std::numeric_limits<float>::is_iec559,
                  "Qt assumes IEEE 754 floating point");
#endif
 
// Technically, presence of NaN and infinities are implied from the above check,
// but double checking our environment doesn't hurt...
static_assert(std::numeric_limits<float>::has_infinity &&
                  std::numeric_limits<float>::has_quiet_NaN,
                  "Qt assumes IEEE 754 floating point");
 
// is_iec559 checks for ISO/IEC/IEEE 60559:2011 (aka IEEE 754-2008) compliance,
// but that allows for a non-binary radix. We need to recheck that.
// Note how __STDC_IEC_559__ would instead check for IEC 60559:1989, aka
// ANSI/IEEE 754−1985, which specifically implies binary floating point numbers.
static_assert(std::numeric_limits<float>::radix == 2,
                  "Qt assumes binary IEEE 754 floating point");
 
// not required by the definition of size_t, but we depend on this
static_assert(sizeof(size_t) == sizeof(void *), "size_t and a pointer don't have the same size");
static_assert(sizeof(size_t) == sizeof(qsizetype)); // implied by the definition
static_assert((std::is_same<qsizetype, qptrdiff>::value));
static_assert(std::is_same_v<std::size_t, size_t>);
 
// Check that our own typedefs are not broken.
static_assert(sizeof(qint8) == 1, "Internal error, qint8 is misdefined");
static_assert(sizeof(qint16)== 2, "Internal error, qint16 is misdefined");
static_assert(sizeof(qint32) == 4, "Internal error, qint32 is misdefined");
static_assert(sizeof(qint64) == 8, "Internal error, qint64 is misdefined");
#ifdef QT_SUPPORTS_INT128
static_assert(sizeof(qint128) == 16, "Internal error, qint128 is misdefined");
#endif
 
#ifdef QT_SUPPORTS_INT128
// Standard Library supports for 128-bit integers:
//  Implementation      | Version | Note
// ---------------------|---------|------
//  GNU libstdc++       | 11.1.0  |
//  LLVM libc++         | 3.5     | May change if compiler has __is_integral()
//  MS STL              | none    |
 
#  if defined(_LIBCPP_VERSION) || (defined(_GLIBCXX_RELEASE) && _GLIBCXX_RELEASE >= 11)
static_assert(std::numeric_limits<quint128>::max() == Q_UINT128_MAX);
#  endif
#endif
 
QT_END_NAMESPACE