llvm-project/libcxx/include/cfenv
Louis Dionne 8cedff10a1 [libc++] Diagnose when header search paths are set up incorrectly
An issue I often see in codebases compiled for unusual platforms is
that header search paths are specified manually and are subtly wrong.
For example, people will manually add `-isystem <some-toolchain>/usr/include`,
which ends up messing up the layering of header search paths required by
libc++ (because the C Standard Library now appears *before* libc++ in
the search paths). Without this patch, this will end up causing
compilation errors that are pretty inscrutable. This patch aims to
improve the user experience by diagnosing this issue explicitly.

In all cases I can think of, I would expect that a compilation error
occur if these header search paths are not layered properly. This
should only provide an explicit diagnostic instead of failing due
to seemingly unrelated compilation errors.

Differential Revision: https://reviews.llvm.org/D131441
2022-08-17 14:05:26 -04:00

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2.4 KiB
C++

// -*- 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_CFENV
#define _LIBCPP_CFENV
/*
cfenv 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
namespace std
{
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);
} // std
*/
#include <__assert> // all public C++ headers provide the assertion handler
#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.
#endif
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
using ::fenv_t _LIBCPP_USING_IF_EXISTS;
using ::fexcept_t _LIBCPP_USING_IF_EXISTS;
using ::feclearexcept _LIBCPP_USING_IF_EXISTS;
using ::fegetexceptflag _LIBCPP_USING_IF_EXISTS;
using ::feraiseexcept _LIBCPP_USING_IF_EXISTS;
using ::fesetexceptflag _LIBCPP_USING_IF_EXISTS;
using ::fetestexcept _LIBCPP_USING_IF_EXISTS;
using ::fegetround _LIBCPP_USING_IF_EXISTS;
using ::fesetround _LIBCPP_USING_IF_EXISTS;
using ::fegetenv _LIBCPP_USING_IF_EXISTS;
using ::feholdexcept _LIBCPP_USING_IF_EXISTS;
using ::fesetenv _LIBCPP_USING_IF_EXISTS;
using ::feupdateenv _LIBCPP_USING_IF_EXISTS;
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP_CFENV