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use if constexpr instead of macros #2686

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Jul 11, 2023
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use if constexpr instead of macros #2686

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52 changes: 16 additions & 36 deletions src/safe_op.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -94,43 +94,23 @@ bool fallback_add_overflow(T summand_1, T summand_2, T& result) {
*/
template <typename T>
bool builtin_add_overflow(T summand_1, T summand_2, T& result) {
return fallback_add_overflow(summand_1, summand_2, result);
}

#if defined(__GNUC__) || defined(__clang__)
#if __GNUC__ >= 5 || __clang_major__ >= 3

/*!
* This macro pastes a specialization of builtin_add_overflow using gcc's &
* clang's __builtin_(s/u)add(l)(l)_overlow()
*
* The add function is implemented by forwarding the parameters to the intrinsic
* and returning its value.
*
* The intrinsics are documented here:
* https://gcc.gnu.org/onlinedocs/gcc/Integer-Overflow-Builtins.html#Integer-Overflow-Builtins
*/
#define SPECIALIZE_builtin_add_overflow(type, builtin_name) \
/* Full specialization of builtin_add_overflow for type using the */ \
/* builtin_name intrinsic */ \
template <> \
constexpr bool builtin_add_overflow<type>(type summand_1, type summand_2, type & result) { \
return builtin_name(summand_1, summand_2, &result); \
}

SPECIALIZE_builtin_add_overflow(int, __builtin_sadd_overflow);
SPECIALIZE_builtin_add_overflow(long, __builtin_saddl_overflow);
SPECIALIZE_builtin_add_overflow(long long, __builtin_saddll_overflow);

SPECIALIZE_builtin_add_overflow(unsigned int, __builtin_uadd_overflow);
SPECIALIZE_builtin_add_overflow(unsigned long, __builtin_uaddl_overflow);
SPECIALIZE_builtin_add_overflow(unsigned long long, __builtin_uaddll_overflow);

#undef SPECIALIZE_builtin_add_overflow
#endif // __GNUC__ >= 5 || __clang_major >= 3

#if (defined(__GNUC__) || defined(__clang__)) && (__GNUC__ >= 5 || __clang_major__ >= 3)
if constexpr (std::is_same_v<T, int>)
return __builtin_sadd_overflow(summand_1, summand_2, &result);
else if constexpr (std::is_same_v<T, long>)
return __builtin_saddl_overflow(summand_1, summand_2, &result);
else if constexpr (std::is_same_v<T, long long>)
return __builtin_saddll_overflow(summand_1, summand_2, &result);
else if constexpr (std::is_same_v<T, unsigned int>)
return __builtin_uadd_overflow(summand_1, summand_2, &result);
else if constexpr (std::is_same_v<T, unsigned long>)
return __builtin_uaddl_overflow(summand_1, summand_2, &result);
else if constexpr (std::is_same_v<T, unsigned long long>)
return __builtin_uaddll_overflow(summand_1, summand_2, &result);
else
#endif

return fallback_add_overflow(summand_1, summand_2, result);
}
} // namespace Internal

/*!
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