5d87f60f89
Some platforms don't provide all C library headers. In practice, libc++
only requires a few C library headers to exist, and only a few functions
on those headers. Missing functions that libc++ doesn't need for its own
implementation are handled properly by the using_if_exists attribute,
however a missing header is currently a hard error when we try to
do #include_next.
This patch should make libc++ more flexible on platforms that do not
provide C headers that libc++ doesn't actually require for its own
implementation. The only downside is that it may move some errors from
the #include_next point to later in the compilation if we actually try
to use something that isn't provided, which could be somewhat confusing.
However, these errors should be caught by folks trying to port libc++
over to a new platform (when running the libc++ test suite), not by end
users.
NOTE: This is a reapplicaton of 226409, which was reverted in 674729813
because it broke the build. The issue has now been fixed with
https://reviews.llvm.org/D138062.
Differential Revision: https://reviews.llvm.org/D136683
69 lines
1.5 KiB
C++
69 lines
1.5 KiB
C++
// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP_LIMITS_H
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#define _LIBCPP_LIMITS_H
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/*
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limits.h synopsis
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Macros:
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CHAR_BIT
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SCHAR_MIN
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SCHAR_MAX
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UCHAR_MAX
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CHAR_MIN
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CHAR_MAX
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MB_LEN_MAX
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SHRT_MIN
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SHRT_MAX
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USHRT_MAX
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INT_MIN
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INT_MAX
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UINT_MAX
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LONG_MIN
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LONG_MAX
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ULONG_MAX
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LLONG_MIN // C99
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LLONG_MAX // C99
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ULLONG_MAX // C99
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*/
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#include <__config>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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#ifndef __GNUC__
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# if __has_include_next(<limits.h>)
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# include_next <limits.h>
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# endif
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#else
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// GCC header limits.h recursively includes itself through another header called
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// syslimits.h for some reason. This setup breaks down if we directly
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// #include_next GCC's limits.h (reasons not entirely clear to me). Therefore,
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// we manually re-create the necessary include sequence below:
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// Get the system limits.h defines (force recurse into the next level)
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#define _GCC_LIMITS_H_
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#define _GCC_NEXT_LIMITS_H
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#include_next <limits.h>
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// Get the ISO C defines
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#undef _GCC_LIMITS_H_
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#include_next <limits.h>
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#endif // __GNUC__
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#endif // _LIBCPP_LIMITS_H
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