include/no_extern_c.h

   1 /**************************************************************************
   2  *
   3  * Copyright 2014 VMware, Inc.
   4  * All Rights Reserved.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a
   7  * copy of this software and associated documentation files (the "Software"),
   8  * to deal in the Software without restriction, including without limitation
   9  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  10  * and/or sell copies of the Software, and to permit persons to whom the
  11  * Software is furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included
  14  * in all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  17  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
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  21  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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  24  **************************************************************************/
  25
  26
  27 /*
  28  * Including system's headers inside `extern "C" { ... }` is not safe, as system
  29  * headers may have C++ code in them, and C++ code inside extern "C"
  30  * leads to syntactically incorrect code.
  31  *
  32  * This is because putting code inside extern "C" won't make __cplusplus define
  33  * go away, that is, the system header being included thinks is free to use C++
  34  * as it sees fits.
  35  *
  36  * Including non-system headers inside extern "C"  is not safe either, because
  37  * non-system headers end up including system headers, hence fall in the above
  38  * case too.
  39  *
  40  * Conclusion, includes inside extern "C" is simply not portable.
  41  *
  42  *
  43  * This header helps surface these issues.
  44  */
  45
  46 #ifdef __cplusplus
  47 template<class T> class _IncludeInsideExternCNotPortable;
  48 #endif