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Bug 1616684. Remove implicit integer conversion in CheckedInt constructor r=froydnj

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When I try to enable -Wconversion, CheckedInt triggers it because it has an
implicit type conversion in its templated two-arg constructor.

That constructor doesn't really need to be templated, as far as I can tell.

Differential Revision: https://phabricator.services.mozilla.com/D63384

--HG--
extra : moz-landing-system : lando
This commit is contained in:
Boris Zbarsky 2020-02-20 14:16:03 +00:00
parent b1f8deb8c6
commit acaa2133b1
1 changed files with 30 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

46
mfbt/CheckedInt.h
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@ -14,6 +14,7 @@
#include "mozilla/Attributes.h"
#include "mozilla/IntegerTypeTraits.h"
#include <limits>
#include <type_traits>
#define MOZILLA_CHECKEDINT_COMPARABLE_VERSION(major, minor, patch) \
(major << 16 | minor << 8 | patch)
@ -408,7 +409,8 @@ struct NegateImpl<T, false> {
static constexpr CheckedInt<T> negate(const CheckedInt<T>& aVal) {
// Handle negation separately for signed/unsigned, for simpler code and to
// avoid an MSVC warning negating an unsigned value.
return CheckedInt<T>(0, aVal.isValid() && aVal.mValue == 0);
static_assert(detail::IsInRange<T>(0), "Integer type can't represent 0");
return CheckedInt<T>(T(0), aVal.isValid() && aVal.mValue == 0);
}
};
@ -420,7 +422,10 @@ struct NegateImpl<T, true> {
if (!aVal.isValid() || aVal.mValue == std::numeric_limits<T>::min()) {
return CheckedInt<T>(aVal.mValue, false);
}
return CheckedInt<T>(-aVal.mValue, true);
/* For some T, arithmetic ops automatically promote to a wider type, so
* explitly do the narrowing cast here. The narrowing cast is valid because
* we did the check for min value above. */
return CheckedInt<T>(T(-aVal.mValue), true);
}
};
@ -506,9 +511,10 @@ class CheckedInt {
template <typename U>
constexpr CheckedInt(U aValue, bool aIsValid)
: mValue(aValue), mIsValid(aIsValid) {
static_assert(
detail::IsSupported<T>::value && detail::IsSupported<U>::value,
"This type is not supported by CheckedInt");
static_assert(std::is_same_v<T, U>,
"this constructor must accept only T values");
static_assert(detail::IsSupported<T>::value,
"This type is not supported by CheckedInt");
}
friend struct detail::NegateImpl<T>;
@ -544,9 +550,10 @@ class CheckedInt {
}
/** Constructs a valid checked integer with initial value 0 */
constexpr CheckedInt() : mValue(0), mIsValid(true) {
constexpr CheckedInt() : mValue(T(0)), mIsValid(true) {
static_assert(detail::IsSupported<T>::value,
"This type is not supported by CheckedInt");
static_assert(detail::IsInRange<T>(0), "Integer type can't represent 0");
}
/** @returns the actual value */
@ -668,15 +675,20 @@ class CheckedInt {
bool operator>=(U aOther) const = delete;
};
#define MOZ_CHECKEDINT_BASIC_BINARY_OPERATOR(NAME, OP) \
template <typename T> \
constexpr CheckedInt<T> operator OP(const CheckedInt<T>& aLhs, \
const CheckedInt<T>& aRhs) { \
if (!detail::Is##NAME##Valid(aLhs.mValue, aRhs.mValue)) { \
return CheckedInt<T>(0, false); \
} \
return CheckedInt<T>(aLhs.mValue OP aRhs.mValue, \
aLhs.mIsValid && aRhs.mIsValid); \
#define MOZ_CHECKEDINT_BASIC_BINARY_OPERATOR(NAME, OP) \
template <typename T> \
constexpr CheckedInt<T> operator OP(const CheckedInt<T>& aLhs, \
const CheckedInt<T>& aRhs) { \
if (!detail::Is##NAME##Valid(aLhs.mValue, aRhs.mValue)) { \
static_assert(detail::IsInRange<T>(0), \
"Integer type can't represent 0"); \
return CheckedInt<T>(T(0), false); \
} \
/* For some T, arithmetic ops automatically promote to a wider type, so \
* explitly do the narrowing cast here. The narrowing cast is valid \
* because we did the "Is##NAME##Valid" check above. */ \
return CheckedInt<T>(T(aLhs.mValue OP aRhs.mValue), \
aLhs.mIsValid && aRhs.mIsValid); \
}
#if MOZ_HAS_BUILTIN_OP_OVERFLOW
@ -686,7 +698,9 @@ class CheckedInt {
const CheckedInt<T>& aRhs) { \
auto result = T{}; \
if (FUN(aLhs.mValue, aRhs.mValue, &result)) { \
return CheckedInt<T>(0, false); \
static_assert(detail::IsInRange<T>(0), \
"Integer type can't represent 0"); \
return CheckedInt<T>(T(0), false); \
} \
return CheckedInt<T>(result, aLhs.mIsValid && aRhs.mIsValid); \
}