[libc] Change UInt integer conversion operators to use standard types.

[lntue]

Summary

This fixes an issue with missing unsigned long conversion on macOS.

[michaelrj]

LGTM

[michaelrj]

libc/src/__support/UInt.h

80–86

nit: it might be best to have both the uint and the standard int types for casting

[lntue]

libc/src/__support/UInt.h

80–86

Adding other uint overload will actually cause ambiguity, as they are simply aliases of these on many platforms. We had similar issues when adding built-in wrappers https://github.com/llvm/llvm-project/blob/main/libc/src/__support/builtin_wrappers.h

libc/src/__support/UInt.h

for (size_t i = 1; i < WORDCOUNT; ++i) {
       val[i] = 0;
     }
   }
   constexpr explicit UInt(const cpp::array<uint64_t, WORDCOUNT> &words) {
     for (size_t i = 0; i < WORDCOUNT; ++i)
       val[i] = words[i];
   }
 
-  constexpr explicit operator uint64_t() const { return val[0]; }
+  constexpr explicit operator unsigned long long() const {
+    return static_cast<unsigned long long>(val[0]);
+  }
+
+  constexpr explicit operator unsigned long() const {
+    return static_cast<unsigned long>(val[0]);
+  }
 
-  constexpr explicit operator uint32_t() const {
-    return uint32_t(uint64_t(*this));
+  constexpr explicit operator unsigned int() const {
+    return static_cast<unsigned int>(val[0]);
   }
 
-  constexpr explicit operator uint16_t() const {
-    return uint16_t(uint64_t(*this));
+  constexpr explicit operator unsigned short() const {
+    return static_cast<unsigned short>(val[0]);
   }
 
-  constexpr explicit operator uint8_t() const {
-    return uint8_t(uint64_t(*this));
+  constexpr explicit operator unsigned char() const {
+    return static_cast<unsigned char>(val[0]);
   }
 
   constexpr explicit operator bool() const { return !is_zero(); }
 
   UInt<Bits> &operator=(const UInt<Bits> &other) = default;
 
   constexpr bool is_zero() const {
     for (size_t i = 0; i < WORDCOUNT; ++i) {