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Reimplement qt_inf/qt_snan/qt_qnan using std::numeric_limits. 

Qt already assumes a working IEEE-754 implementation, so we can rely
on a working std::numeric_limits<double>.

This patch also gets rid of three cases of type-punning with unions
(which is undefined behavior in C++).

Change-Id: Ic3747f49d55e372960abf2091c1d5752c1eccdff
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
bb10
Erik Verbruggen 2015-08-10 13:22:38 +02:00
parent c7934f2489
commit 72c68f5f22
1 changed files with 14 additions and 70 deletions
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84
src/corelib/global/qnumeric_p.h
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@ -107,85 +107,29 @@ static inline bool isfinite(float f) { return std::isfinite(f); }
#endif
}
#if !defined(Q_CC_MIPS)
static const union { unsigned char c[8]; double d; } qt_be_inf_bytes = { { 0x7f, 0xf0, 0, 0, 0, 0, 0, 0 } };
static const union { unsigned char c[8]; double d; } qt_le_inf_bytes = { { 0, 0, 0, 0, 0, 0, 0xf0, 0x7f } };
static inline double qt_inf()
Q_DECL_CONSTEXPR static inline double qt_inf() Q_DECL_NOEXCEPT
{
return (QSysInfo::ByteOrder == QSysInfo::BigEndian
? qt_be_inf_bytes.d
: qt_le_inf_bytes.d);
Q_STATIC_ASSERT_X(std::numeric_limits<double>::has_infinity,
"platform has no definition for infinity for type double");
return std::numeric_limits<double>::infinity();
}
// Signaling NAN
static const union { unsigned char c[8]; double d; } qt_be_snan_bytes = { { 0x7f, 0xf8, 0, 0, 0, 0, 0, 0 } };
static const union { unsigned char c[8]; double d; } qt_le_snan_bytes = { { 0, 0, 0, 0, 0, 0, 0xf8, 0x7f } };
static inline double qt_snan()
// Signaling NaN
Q_DECL_CONSTEXPR static inline double qt_snan() Q_DECL_NOEXCEPT
{
return (QSysInfo::ByteOrder == QSysInfo::BigEndian
? qt_be_snan_bytes.d
: qt_le_snan_bytes.d);
Q_STATIC_ASSERT_X(std::numeric_limits<double>::has_signaling_NaN,
"platform has no definition for signaling NaN for type double");
return std::numeric_limits<double>::signaling_NaN();
}
// Quiet NAN
static const union { unsigned char c[8]; double d; } qt_be_qnan_bytes = { { 0xff, 0xf8, 0, 0, 0, 0, 0, 0 } };
static const union { unsigned char c[8]; double d; } qt_le_qnan_bytes = { { 0, 0, 0, 0, 0, 0, 0xf8, 0xff } };
static inline double qt_qnan()
// Quiet NaN
Q_DECL_CONSTEXPR static inline double qt_qnan() Q_DECL_NOEXCEPT
{
return (QSysInfo::ByteOrder == QSysInfo::BigEndian
? qt_be_qnan_bytes.d
: qt_le_qnan_bytes.d);
Q_STATIC_ASSERT_X(std::numeric_limits<double>::has_quiet_NaN,
"platform has no definition for quiet NaN for type double");
return std::numeric_limits<double>::quiet_NaN();
}
#else // Q_CC_MIPS
static const unsigned char qt_be_inf_bytes[] = { 0x7f, 0xf0, 0, 0, 0, 0, 0, 0 };
static const unsigned char qt_le_inf_bytes[] = { 0, 0, 0, 0, 0, 0, 0xf0, 0x7f };
static inline double qt_inf()
{
const unsigned char *bytes;
bytes = (QSysInfo::ByteOrder == QSysInfo::BigEndian
? qt_be_inf_bytes
: qt_le_inf_bytes);
union { unsigned char c[8]; double d; } returnValue;
memcpy(returnValue.c, bytes, sizeof(returnValue.c));
return returnValue.d;
}
// Signaling NAN
static const unsigned char qt_be_snan_bytes[] = { 0x7f, 0xf8, 0, 0, 0, 0, 0, 0 };
static const unsigned char qt_le_snan_bytes[] = { 0, 0, 0, 0, 0, 0, 0xf8, 0x7f };
static inline double qt_snan()
{
const unsigned char *bytes;
bytes = (QSysInfo::ByteOrder == QSysInfo::BigEndian
? qt_be_snan_bytes
: qt_le_snan_bytes);
union { unsigned char c[8]; double d; } returnValue;
memcpy(returnValue.c, bytes, sizeof(returnValue.c));
return returnValue.d;
}
// Quiet NAN
static const unsigned char qt_be_qnan_bytes[] = { 0xff, 0xf8, 0, 0, 0, 0, 0, 0 };
static const unsigned char qt_le_qnan_bytes[] = { 0, 0, 0, 0, 0, 0, 0xf8, 0xff };
static inline double qt_qnan()
{
const unsigned char *bytes;
bytes = (QSysInfo::ByteOrder == QSysInfo::BigEndian
? qt_be_qnan_bytes
: qt_le_qnan_bytes);
union { unsigned char c[8]; double d; } returnValue;
memcpy(returnValue.c, bytes, sizeof(returnValue.c));
return returnValue.d;
}
#endif // Q_CC_MIPS
static inline bool qt_is_inf(double d)
{
return qnumeric_std_wrapper::isinf(d);