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Bug 1030515 - Make IsSigned and IsUnsigned usable with user-defined types. r=froydnj

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--HG--
extra : rebase_source : f74d5c0b9f05a56c4d56aba1ebbdb944a3464b30
This commit is contained in:
Jeff Walden 2014-06-25 18:47:04 -07:00
parent 9c75cdfbfa
commit 297cdb7279
2 changed files with 30 additions and 13 deletions
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33
mfbt/TypeTraits.h
View File

@ -417,26 +417,30 @@ namespace detail {
template<typename T,
bool = IsFloatingPoint<T>::value,
bool = IsIntegral<T>::value,
typename NoCV = typename RemoveCV<T>::Type>
struct IsSignedHelper;
// Floating point is signed.
template<typename T, typename NoCV>
struct IsSignedHelper<T, true, NoCV> : TrueType {};
struct IsSignedHelper<T, true, false, NoCV> : TrueType {};
// Integral is conditionally signed.
template<typename T, typename NoCV>
struct IsSignedHelper<T, false, NoCV>
: IntegralConstant<bool, IsArithmetic<T>::value && NoCV(-1) < NoCV(1)>
struct IsSignedHelper<T, false, true, NoCV>
: IntegralConstant<bool, bool(NoCV(-1) < NoCV(1))>
{};
// Non-floating point, non-integral is not signed.
template<typename T, typename NoCV>
struct IsSignedHelper<T, false, false, NoCV> : FalseType {};
} // namespace detail
/**
* IsSigned determines whether a type is a signed arithmetic type. |char| is
* considered a signed type if it has the same representation as |signed char|.
*
* Don't use this if the type might be user-defined! You might or might not get
* a compile error, depending.
*
* mozilla::IsSigned<int>::value is true;
* mozilla::IsSigned<const unsigned int>::value is false;
* mozilla::IsSigned<unsigned char>::value is false;
@ -449,27 +453,30 @@ namespace detail {
template<typename T,
bool = IsFloatingPoint<T>::value,
bool = IsIntegral<T>::value,
typename NoCV = typename RemoveCV<T>::Type>
struct IsUnsignedHelper;
// Floating point is not unsigned.
template<typename T, typename NoCV>
struct IsUnsignedHelper<T, true, NoCV> : FalseType {};
struct IsUnsignedHelper<T, true, false, NoCV> : FalseType {};
// Integral is conditionally unsigned.
template<typename T, typename NoCV>
struct IsUnsignedHelper<T, false, NoCV>
struct IsUnsignedHelper<T, false, true, NoCV>
: IntegralConstant<bool,
IsArithmetic<T>::value &&
(IsSame<NoCV, bool>::value || NoCV(1) < NoCV(-1))>
(IsSame<NoCV, bool>::value || bool(NoCV(1) < NoCV(-1)))>
{};
// Non-floating point, non-integral is not unsigned.
template<typename T, typename NoCV>
struct IsUnsignedHelper<T, false, false, NoCV> : FalseType {};
} // namespace detail
/**
* IsUnsigned determines whether a type is an unsigned arithmetic type.
*
* Don't use this if the type might be user-defined! You might or might not get
* a compile error, depending.
*
* mozilla::IsUnsigned<int>::value is false;
* mozilla::IsUnsigned<const unsigned int>::value is true;
* mozilla::IsUnsigned<unsigned char>::value is true;

10
mfbt/tests/TestTypeTraits.cpp
View File

@ -153,6 +153,16 @@ static_assert(IsSigned<const volatile long double>::value,
static_assert(!IsUnsigned<const volatile long double>::value,
"const volatile long double shouldn't be unsigned");
class NotIntConstructible
{
NotIntConstructible(int) MOZ_DELETE;
};
static_assert(!IsSigned<NotIntConstructible>::value,
"non-arithmetic types are not signed");
static_assert(!IsUnsigned<NotIntConstructible>::value,
"non-arithmetic types are not unsigned");
namespace CPlusPlus11IsBaseOf {
// Adapted from C++11 § 20.9.6.