[libcxx-commits] [libcxx] [libc++][NFC] Simplify the implementation of __mul_overflowed (PR #174956)

[Nikolas Klauser via libcxx-commits]

https://github.com/philnik777 created https://github.com/llvm/llvm-project/pull/174956

`__builtin_mul_overflow` does the right thing, even for `char` and `short`, so the overloads for these types can simply be dropped. We can also merge the remaining two overloads into a single one now, since we don't do any dispatching for `char` and `short` anymore.


>From e665a2f923cef9c302fed011dc0c175c6fd6d8ef Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser at berlin.de>
Date: Thu, 8 Jan 2026 13:01:38 +0100
Subject: [PATCH] [libc++][NFC] Simplify the implementation of __mul_overflowed

---
 libcxx/include/__charconv/traits.h | 27 +++------------------------
 1 file changed, 3 insertions(+), 24 deletions(-)

diff --git a/libcxx/include/__charconv/traits.h b/libcxx/include/__charconv/traits.h
index 9fd0092ca79c3..b8c840d1ebe32 100644
--- a/libcxx/include/__charconv/traits.h
+++ b/libcxx/include/__charconv/traits.h
@@ -113,31 +113,10 @@ struct _LIBCPP_HIDDEN __traits_base<_Tp, __enable_if_t<sizeof(_Tp) == sizeof(__u
 };
 #  endif
 
-template <typename _Tp>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool
-__mul_overflowed(unsigned char __a, _Tp __b, unsigned char& __r) {
-  auto __c = __a * __b;
-  __r      = __c;
-  return __c > numeric_limits<unsigned char>::max();
-}
-
-template <typename _Tp>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool
-__mul_overflowed(unsigned short __a, _Tp __b, unsigned short& __r) {
-  auto __c = __a * __b;
-  __r      = __c;
-  return __c > numeric_limits<unsigned short>::max();
-}
-
-template <typename _Tp>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool __mul_overflowed(_Tp __a, _Tp __b, _Tp& __r) {
-  static_assert(is_unsigned<_Tp>::value, "");
-  return __builtin_mul_overflow(__a, __b, std::addressof(__r));
-}
-
 template <typename _Tp, typename _Up>
-inline _LIBCPP_HIDE_FROM_ABI bool _LIBCPP_CONSTEXPR_SINCE_CXX23 __mul_overflowed(_Tp __a, _Up __b, _Tp& __r) {
-  return __itoa::__mul_overflowed(__a, static_cast<_Tp>(__b), __r);
+_LIBCPP_HIDE_FROM_ABI bool _LIBCPP_CONSTEXPR_SINCE_CXX23 __mul_overflowed(_Tp __a, _Up __b, _Tp& __r) {
+  static_assert(is_unsigned<_Tp>::value);
+  return __builtin_mul_overflow(__a, static_cast<_Tp>(__b), std::addressof(__r));
 }
 
 template <typename _Tp>