Index: include/CMakeLists.txt
===================================================================
--- include/CMakeLists.txt
+++ include/CMakeLists.txt
@@ -95,6 +95,7 @@
   ext/__hash
   ext/hash_map
   ext/hash_set
+  fenv.h
   filesystem
   float.h
   forward_list
Index: include/fenv.h
===================================================================
--- include/fenv.h
+++ include/fenv.h
@@ -0,0 +1,204 @@
+// -*- C++ -*-
+//===---------------------------- math.h ----------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_FENV_H
+#define _LIBCPP_FENV_H
+
+
+/*
+    fenv.h synopsis
+
+This entire header is C99 / C++0X
+
+Macros:
+
+    FE_DIVBYZERO
+    FE_INEXACT
+    FE_INVALID
+    FE_OVERFLOW
+    FE_UNDERFLOW
+    FE_ALL_EXCEPT
+    FE_DOWNWARD
+    FE_TONEAREST
+    FE_TOWARDZERO
+    FE_UPWARD
+    FE_DFL_ENV
+
+Types:
+
+    fenv_t
+    fexcept_t
+
+int feclearexcept(int excepts);
+int fegetexceptflag(fexcept_t* flagp, int excepts);
+int feraiseexcept(int excepts);
+int fesetexceptflag(const fexcept_t* flagp, int excepts);
+int fetestexcept(int excepts);
+int fegetround();
+int fesetround(int round);
+int fegetenv(fenv_t* envp);
+int feholdexcept(fenv_t* envp);
+int fesetenv(const fenv_t* envp);
+int feupdateenv(const fenv_t* envp);
+
+
+*/
+
+#include <__config>
+#include_next <fenv.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+#ifdef __cplusplus
+
+extern "C++" {
+
+#ifdef feclearexcept
+_LIBCPP_INLINE_VISIBILITY
+inline int __libcpp_feclearexcept(int __excepts) {
+  return feclearexcept(__excepts);
+}
+#undef feclearexcept
+_LIBCPP_INLINE_VISIBILITY
+inline int feclearexcept(int __excepts) {
+  return ::__libcpp_feclearexcept(__excepts);
+}
+#endif // defined(feclearexcept)
+
+#ifdef fegetexceptflag
+_LIBCPP_INLINE_VISIBILITY
+inline int __libcpp_fegetexceptflag(fexcept_t* __out_ptr, int __excepts) {
+  return fegetexceptflag(__out_ptr, __excepts);
+}
+#undef fegetexceptflag
+_LIBCPP_INLINE_VISIBILITY
+inline int fegetexceptflag(fexcept_t *__out_ptr, int __excepts) {
+  return ::__libcpp_fegetexceptflag(__out_ptr, __excepts);
+}
+#endif // defined(fegetexceptflag)
+
+
+#ifdef feraiseexcept
+_LIBCPP_INLINE_VISIBILITY
+inline int __libcpp_feraiseexcept(int __excepts) {
+  return feraiseexcept(__excepts);
+}
+#undef feraiseexcept
+_LIBCPP_INLINE_VISIBILITY
+inline int feraiseexcept(int __excepts) {
+  return ::__libcpp_feraiseexcept(__excepts);
+}
+#endif // defined(feraiseexcept)
+
+
+#ifdef fesetexceptflag
+_LIBCPP_INLINE_VISIBILITY
+inline int __libcpp_fesetexceptflag(const fexcept_t* __out_ptr, int __excepts) {
+  return fesetexceptflag(__out_ptr, __excepts);
+}
+#undef fesetexceptflag
+_LIBCPP_INLINE_VISIBILITY
+inline int fesetexceptflag(const fexcept_t *__out_ptr, int __excepts) {
+  return ::__libcpp_fesetexceptflag(__out_ptr, __excepts);
+}
+#endif // defined(fesetexceptflag)
+
+
+#ifdef fetestexcept
+_LIBCPP_INLINE_VISIBILITY
+inline int __libcpp_fetestexcept(int __excepts) {
+  return fetestexcept(__excepts);
+}
+#undef fetestexcept
+_LIBCPP_INLINE_VISIBILITY
+inline int fetestexcept(int __excepts) {
+  return ::__libcpp_fetestexcept(__excepts);
+}
+#endif // defined(fetestexcept)
+
+#ifdef fegetround
+_LIBCPP_INLINE_VISIBILITY
+inline int __libcpp_fegetround() {
+  return fegetround();
+}
+#undef fegetround
+_LIBCPP_INLINE_VISIBILITY
+inline int fegetround() {
+  return ::__libcpp_fegetround();
+}
+#endif // defined(fegetround)
+
+#ifdef fesetround
+_LIBCPP_INLINE_VISIBILITY
+inline int __libcpp_fesetround(int __round) {
+  return fesetround(__round);
+}
+#undef fesetround
+_LIBCPP_INLINE_VISIBILITY
+inline int fesetround(int __round) {
+  return ::__libcpp_fesetround(__round);
+}
+#endif // defined(fesetround)
+
+#ifdef fegetenv
+_LIBCPP_INLINE_VISIBILITY
+inline int __libcpp_fegetenv(fenv_t* __envp) {
+  return fegetenv(__envp);
+}
+#undef fegetenv
+_LIBCPP_INLINE_VISIBILITY
+inline int fegetenv(fenv_t* __envp) {
+  return ::__libcpp_fegetenv(__envp);
+}
+#endif // defined(fegetenv)
+
+#ifdef feholdexcept
+_LIBCPP_INLINE_VISIBILITY
+inline int __libcpp_feholdexcept(fenv_t* __envp) {
+  return feholdexcept(__envp);
+}
+#undef feholdexcept
+_LIBCPP_INLINE_VISIBILITY
+inline int feholdexcept(fenv_t* __envp) {
+  return ::__libcpp_feholdexcept(__envp);
+}
+#endif // defined(feholdexcept)
+
+
+#ifdef fesetenv
+_LIBCPP_INLINE_VISIBILITY
+inline int __libcpp_fesetenv(const fenv_t* __envp) {
+  return fesetenv(__envp);
+}
+#undef fesetenv
+_LIBCPP_INLINE_VISIBILITY
+inline int fesetenv(const fenv_t* __envp) {
+  return ::__libcpp_fesetenv(__envp);
+}
+#endif // defined(fesetenv)
+
+#ifdef feupdateenv
+_LIBCPP_INLINE_VISIBILITY
+inline int __libcpp_feupdateenv(const fenv_t* __envp) {
+  return feupdateenv(__envp);
+}
+#undef feupdateenv
+_LIBCPP_INLINE_VISIBILITY
+inline int feupdateenv(const fenv_t* __envp) {
+  return ::__libcpp_feupdateenv(__envp);
+}
+#endif // defined(feupdateenv)
+
+} // extern "C++"
+
+#endif // defined(__cplusplus)
+
+#endif // _LIBCPP_FENV_H
Index: include/module.modulemap
===================================================================
--- include/module.modulemap
+++ include/module.modulemap
@@ -24,7 +24,10 @@
       header "errno.h"
       export *
     }
-    // <fenv.h> provided by C library.
+    module fenv_h {
+      header "fenv.h"
+      export *
+    }
     // <float.h> provided by compiler or C library.
     module inttypes_h {
       header "inttypes.h"
Index: test/libcxx/depr/depr.c.headers/fenv.pass.cpp
===================================================================
--- test/libcxx/depr/depr.c.headers/fenv.pass.cpp
+++ test/libcxx/depr/depr.c.headers/fenv.pass.cpp
@@ -0,0 +1,19 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <fenv.h>
+
+#include <fenv.h>
+
+#ifndef _LIBCPP_VERSION
+#error _LIBCPP_VERSION not defined
+#endif
+
+int main()
+{
+}
Index: test/libcxx/double_include.sh.cpp
===================================================================
--- test/libcxx/double_include.sh.cpp
+++ test/libcxx/double_include.sh.cpp
@@ -63,6 +63,7 @@
 #include <deque>
 #include <errno.h>
 #include <exception>
+#include <fenv.h>
 #include <filesystem>
 #include <float.h>
 #include <forward_list>
Index: test/libcxx/include_as_c.sh.cpp
===================================================================
--- test/libcxx/include_as_c.sh.cpp
+++ test/libcxx/include_as_c.sh.cpp
@@ -17,6 +17,7 @@
 #include <complex.h>
 #include <ctype.h>
 #include <errno.h>
+#include <fenv.h>
 #include <float.h>
 #include <inttypes.h>
 #include <limits.h>
Index: test/std/depr/depr.c.headers/fenv_h.pass.cpp
===================================================================
--- test/std/depr/depr.c.headers/fenv_h.pass.cpp
+++ test/std/depr/depr.c.headers/fenv_h.pass.cpp
@@ -61,17 +61,17 @@
 {
     fenv_t fenv = {};
     fexcept_t fex = 0;
-    static_assert((std::is_same<decltype(feclearexcept(0)), int>::value), "");
-    static_assert((std::is_same<decltype(fegetexceptflag(&fex, 0)), int>::value), "");
-    static_assert((std::is_same<decltype(feraiseexcept(0)), int>::value), "");
-    static_assert((std::is_same<decltype(fesetexceptflag(&fex, 0)), int>::value), "");
-    static_assert((std::is_same<decltype(fetestexcept(0)), int>::value), "");
-    static_assert((std::is_same<decltype(fegetround()), int>::value), "");
-    static_assert((std::is_same<decltype(fesetround(0)), int>::value), "");
-    static_assert((std::is_same<decltype(fegetenv(&fenv)), int>::value), "");
-    static_assert((std::is_same<decltype(feholdexcept(&fenv)), int>::value), "");
-    static_assert((std::is_same<decltype(fesetenv(&fenv)), int>::value), "");
-    static_assert((std::is_same<decltype(feupdateenv(&fenv)), int>::value), "");
+    static_assert((std::is_same<decltype(::feclearexcept(0)), int>::value), "");
+    static_assert((std::is_same<decltype(::fegetexceptflag(&fex, 0)), int>::value), "");
+    static_assert((std::is_same<decltype(::feraiseexcept(0)), int>::value), "");
+    static_assert((std::is_same<decltype(::fesetexceptflag(&fex, 0)), int>::value), "");
+    static_assert((std::is_same<decltype(::fetestexcept(0)), int>::value), "");
+    static_assert((std::is_same<decltype(::fegetround()), int>::value), "");
+    static_assert((std::is_same<decltype(::fesetround(0)), int>::value), "");
+    static_assert((std::is_same<decltype(::fegetenv(&fenv)), int>::value), "");
+    static_assert((std::is_same<decltype(::feholdexcept(&fenv)), int>::value), "");
+    static_assert((std::is_same<decltype(::fesetenv(&fenv)), int>::value), "");
+    static_assert((std::is_same<decltype(::feupdateenv(&fenv)), int>::value), "");
 
   return 0;
 }