[libcxx-commits] [libcxx] [libc++] Remove libc++'s own fenv.h (PR #194629)

[Nikolas Klauser via libcxx-commits]

https://github.com/philnik777 created https://github.com/llvm/llvm-project/pull/194629

Our own `fenv.h` only `#undef`s macros which the C header might define. None of the libcs we support define any of these functions as macros, so we can simply drop the header.


>From df7b9cab2825e7eb91698139c40176782b1c2ba4 Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser at berlin.de>
Date: Tue, 28 Apr 2026 15:34:58 +0200
Subject: [PATCH] [libc++] Remove libc++'s own fenv.h

---
 libcxx/include/CMakeLists.txt      |   1 -
 libcxx/include/__cxx03/cfenv       |  10 +--
 libcxx/include/cfenv               |  10 +--
 libcxx/include/fenv.h              | 118 -----------------------------
 libcxx/include/module.modulemap.in |   4 -
 5 files changed, 4 insertions(+), 139 deletions(-)
 delete mode 100644 libcxx/include/fenv.h

diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index 69a6590d18f85..f6d946a4ac58c 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -1034,7 +1034,6 @@ set(files
   ext/__hash
   ext/hash_map
   ext/hash_set
-  fenv.h
   filesystem
   flat_map
   flat_set
diff --git a/libcxx/include/__cxx03/cfenv b/libcxx/include/__cxx03/cfenv
index d3a5839221a82..8658ff20d5253 100644
--- a/libcxx/include/__cxx03/cfenv
+++ b/libcxx/include/__cxx03/cfenv
@@ -54,14 +54,8 @@ int feupdateenv(const fenv_t* envp);
 
 #include <__cxx03/__config>
 
-#include <fenv.h>
-
-#ifndef _LIBCPP_FENV_H
-#   error <cfenv> tried including <fenv.h> but didn't find libc++'s <fenv.h> header. \
-          This usually means that your header search paths are not configured properly. \
-          The header search paths should contain the C++ Standard Library headers before \
-          any C Standard Library, and you are probably using compiler flags that make that \
-          not be the case.
+#if __has_include(<fenv.h>)
+#  include <fenv.h>
 #endif
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/cfenv b/libcxx/include/cfenv
index d7ea770297530..ec7091103d36c 100644
--- a/libcxx/include/cfenv
+++ b/libcxx/include/cfenv
@@ -57,14 +57,8 @@ int feupdateenv(const fenv_t* envp);
 #else
 #  include <__config>
 
-#  include <fenv.h>
-
-#  ifndef _LIBCPP_FENV_H
-#   error <cfenv> tried including <fenv.h> but didn't find libc++'s <fenv.h> header. \
-          This usually means that your header search paths are not configured properly. \
-          The header search paths should contain the C++ Standard Library headers before \
-          any C Standard Library, and you are probably using compiler flags that make that \
-          not be the case.
+#  if __has_include(<fenv.h>)
+#    include <fenv.h>
 #  endif
 
 #  if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/fenv.h b/libcxx/include/fenv.h
deleted file mode 100644
index a767269b5c989..0000000000000
--- a/libcxx/include/fenv.h
+++ /dev/null
@@ -1,118 +0,0 @@
-// -*- C++ -*-
-//===----------------------------------------------------------------------===//
-//
-// 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);
-
-
-*/
-
-#if defined(__cplusplus) && __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
-#  include <__cxx03/__config>
-#else
-#  include <__config>
-#endif
-
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#  pragma GCC system_header
-#endif
-
-#if __has_include_next(<fenv.h>)
-#  include_next <fenv.h>
-#endif
-
-#ifdef __cplusplus
-
-extern "C++" {
-
-#  ifdef feclearexcept
-#    undef feclearexcept
-#  endif
-
-#  ifdef fegetexceptflag
-#    undef fegetexceptflag
-#  endif
-
-#  ifdef feraiseexcept
-#    undef feraiseexcept
-#  endif
-
-#  ifdef fesetexceptflag
-#    undef fesetexceptflag
-#  endif
-
-#  ifdef fetestexcept
-#    undef fetestexcept
-#  endif
-
-#  ifdef fegetround
-#    undef fegetround
-#  endif
-
-#  ifdef fesetround
-#    undef fesetround
-#  endif
-
-#  ifdef fegetenv
-#    undef fegetenv
-#  endif
-
-#  ifdef feholdexcept
-#    undef feholdexcept
-#  endif
-
-#  ifdef fesetenv
-#    undef fesetenv
-#  endif
-
-#  ifdef feupdateenv
-#    undef feupdateenv
-#  endif
-
-} // extern "C++"
-
-#endif // defined(__cplusplus)
-
-#endif // _LIBCPP_FENV_H
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
index b7c2ef91be551..c0c191a445cf3 100644
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -2450,10 +2450,6 @@ module std_errno_h [system] {
   header "errno.h"
   export *
 }
-module std_fenv_h [system] {
-  header "fenv.h"
-  export *
-}
 module std_inttypes_h [system] {
   header "inttypes.h"
   export *