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Use std::memcpy instead of a union to access floating point bits.

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PiperOrigin-RevId: 752789717
Change-Id: I20d17677bc75d12fa50328feb2bdc5c25e852cc4
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Laramie Leavitt 2025-04-29 10:26:11 -07:00 committed by Copybara-Service
parent 00b2154e8e
commit 59c924bc47
1 changed files with 13 additions and 21 deletions
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34
googletest/include/gtest/internal/gtest-internal.h
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@ -290,17 +290,17 @@ class FloatingPoint {
// around may change its bits, although the new value is guaranteed // around may change its bits, although the new value is guaranteed
// to be also a NAN. Therefore, don't expect this constructor to // to be also a NAN. Therefore, don't expect this constructor to
// preserve the bits in x when x is a NAN. // preserve the bits in x when x is a NAN.
explicit FloatingPoint(const RawType& x) { u_.value_ = x; } explicit FloatingPoint(RawType x) { memcpy(&bits_, &x, sizeof(x)); }
// Static methods // Static methods
// Reinterprets a bit pattern as a floating-point number. // Reinterprets a bit pattern as a floating-point number.
// //
// This function is needed to test the AlmostEquals() method. // This function is needed to test the AlmostEquals() method.
static RawType ReinterpretBits(const Bits bits) { static RawType ReinterpretBits(Bits bits) {
FloatingPoint fp(0); RawType fp;
fp.u_.bits_ = bits; memcpy(&fp, &bits, sizeof(fp));
return fp.u_.value_; return fp;
} }
// Returns the floating-point number that represent positive infinity. // Returns the floating-point number that represent positive infinity.
@ -309,16 +309,16 @@ class FloatingPoint {
// Non-static methods // Non-static methods
// Returns the bits that represents this number. // Returns the bits that represents this number.
const Bits& bits() const { return u_.bits_; } const Bits& bits() const { return bits_; }
// Returns the exponent bits of this number. // Returns the exponent bits of this number.
Bits exponent_bits() const { return kExponentBitMask & u_.bits_; } Bits exponent_bits() const { return kExponentBitMask & bits_; }
// Returns the fraction bits of this number. // Returns the fraction bits of this number.
Bits fraction_bits() const { return kFractionBitMask & u_.bits_; } Bits fraction_bits() const { return kFractionBitMask & bits_; }
// Returns the sign bit of this number. // Returns the sign bit of this number.
Bits sign_bit() const { return kSignBitMask & u_.bits_; } Bits sign_bit() const { return kSignBitMask & bits_; }
// Returns true if and only if this is NAN (not a number). // Returns true if and only if this is NAN (not a number).
bool is_nan() const { bool is_nan() const {
@ -338,17 +338,10 @@ class FloatingPoint {
// a NAN must return false. // a NAN must return false.
if (is_nan() || rhs.is_nan()) return false; if (is_nan() || rhs.is_nan()) return false;
return DistanceBetweenSignAndMagnitudeNumbers(u_.bits_, rhs.u_.bits_) <= return DistanceBetweenSignAndMagnitudeNumbers(bits_, rhs.bits_) <= kMaxUlps;
kMaxUlps;
} }
private: private:
// The data type used to store the actual floating-point number.
union FloatingPointUnion {
RawType value_; // The raw floating-point number.
Bits bits_; // The bits that represent the number.
};
// Converts an integer from the sign-and-magnitude representation to // Converts an integer from the sign-and-magnitude representation to
// the biased representation. More precisely, let N be 2 to the // the biased representation. More precisely, let N be 2 to the
// power of (kBitCount - 1), an integer x is represented by the // power of (kBitCount - 1), an integer x is represented by the
@ -364,7 +357,7 @@ class FloatingPoint {
// //
// Read https://en.wikipedia.org/wiki/Signed_number_representations // Read https://en.wikipedia.org/wiki/Signed_number_representations
// for more details on signed number representations. // for more details on signed number representations.
static Bits SignAndMagnitudeToBiased(const Bits& sam) { static Bits SignAndMagnitudeToBiased(Bits sam) {
if (kSignBitMask & sam) { if (kSignBitMask & sam) {
// sam represents a negative number. // sam represents a negative number.
return ~sam + 1; return ~sam + 1;
@ -376,14 +369,13 @@ class FloatingPoint {
// Given two numbers in the sign-and-magnitude representation, // Given two numbers in the sign-and-magnitude representation,
// returns the distance between them as an unsigned number. // returns the distance between them as an unsigned number.
static Bits DistanceBetweenSignAndMagnitudeNumbers(const Bits& sam1, static Bits DistanceBetweenSignAndMagnitudeNumbers(Bits sam1, Bits sam2) {
const Bits& sam2) {
const Bits biased1 = SignAndMagnitudeToBiased(sam1); const Bits biased1 = SignAndMagnitudeToBiased(sam1);
const Bits biased2 = SignAndMagnitudeToBiased(sam2); const Bits biased2 = SignAndMagnitudeToBiased(sam2);
return (biased1 >= biased2) ? (biased1 - biased2) : (biased2 - biased1); return (biased1 >= biased2) ? (biased1 - biased2) : (biased2 - biased1);
} }
FloatingPointUnion u_; Bits bits_; // The bits that represent the number.
}; };
// Typedefs the instances of the FloatingPoint template class that we // Typedefs the instances of the FloatingPoint template class that we