[libcxx-commits] [libcxx] [libc++] Fix hypotf linker error with Clang modules on Windows UCRT (PR #209403)

[A. Jiang via libcxx-commits]

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@@ -27,19 +27,35 @@
 _LIBCPP_PUSH_MACROS
 #include <__undef_macros>
 
+#if defined(_LIBCPP_MSVCRT)
+extern "C" {
+_LIBCPP_CRT_FUNC float __cdecl _hypotf(float, float);
+}
+#endif
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace __math {
 
-inline _LIBCPP_HIDE_FROM_ABI float hypot(float __x, float __y) _NOEXCEPT { return __builtin_hypotf(__x, __y); }
+inline _LIBCPP_HIDE_FROM_ABI float hypot(float __x, float __y) _NOEXCEPT {
+#if defined(_LIBCPP_MSVCRT)
+  return ::_hypotf(__x, __y);
+#else
+  return __builtin_hypotf(__x, __y);
+#endif
+}
 
 template <class = int>
 _LIBCPP_HIDE_FROM_ABI double hypot(double __x, double __y) _NOEXCEPT {
   return __builtin_hypot(__x, __y);
 }
 
 inline _LIBCPP_HIDE_FROM_ABI long double hypot(long double __x, long double __y) _NOEXCEPT {
+#if defined(_LIBCPP_MSVCRT)
+  return (long double)__math::hypot((double)__x, (double)__y);
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frederick-vs-ja wrote:

Also, do we want to explicitly cast a `double` value to `long double` given the conversion is widening?

https://github.com/llvm/llvm-project/pull/209403