pitrou commented on code in PR #55457:
URL: https://github.com/apache/arrow/pull/55457#discussion_r4514839495
##########
cpp/src/parquet/column_reader.cc:
##########
@@ -83,10 +83,28 @@ inline void CheckNumberDecoded(int64_t number_decoded,
int64_t expected) {
}
}
-/// True if a T can hold a U.
+/// True if an integer type T can hold every value of integer type U.
+///
+/// Written in terms of std::numeric_limits rather than std::in_range because
+/// the libc++ in the macOS 11.3 SDK used by CRAN does not provide the latter.
+template <typename T, typename U>
+struct CanHold {
+ static_assert(std::is_integral_v<T> && std::is_integral_v<U>,
+ "can_hold_v is only defined for integer types");
+ static constexpr bool value =
+ std::numeric_limits<T>::digits >= std::numeric_limits<U>::digits &&
+ (std::is_signed_v<T> || !std::is_signed_v<U>);
+};
+
template <typename T, typename U>
-inline constexpr bool can_hold_v =
std::in_range<T>(std::numeric_limits<U>::min()) &&
-
std::in_range<T>(std::numeric_limits<U>::max());
+inline constexpr bool can_hold_v = CanHold<T, U>::value;
+
+static_assert(can_hold_v<int64_t, int32_t>);
+static_assert(can_hold_v<int64_t, uint32_t>);
+static_assert(can_hold_v<int32_t, int32_t>);
+static_assert(!can_hold_v<int32_t, int64_t>);
+static_assert(!can_hold_v<int32_t, uint32_t>);
Review Comment:
The converse should hold true as well?
```suggestion
static_assert(!can_hold_v<int32_t, uint32_t>);
static_assert(!can_hold_v<uint32_t, int32_t>);
```
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