ceres/macros.h

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// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2010, 2011, 2012 Google Inc. All rights reserved.
// http://code.google.com/p/ceres-solver/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice,
//   this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright notice,
//   this list of conditions and the following disclaimer in the documentation
//   and/or other materials provided with the distribution.
// * Neither the name of Google Inc. nor the names of its contributors may be
//   used to endorse or promote products derived from this software without
//   specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
//
//
// Various Google-specific macros.
//
// This code is compiled directly on many platforms, including client
// platforms like Windows, Mac, and embedded systems.  Before making
// any changes here, make sure that you're not breaking any platforms.

#ifndef CERES_PUBLIC_INTERNAL_MACROS_H_
#define CERES_PUBLIC_INTERNAL_MACROS_H_

#include <cstddef>  // For size_t.

// A macro to disallow the copy constructor and operator= functions
// This should be used in the private: declarations for a class
//
// For disallowing only assign or copy, write the code directly, but declare
// the intend in a comment, for example:
//
//   void operator=(const TypeName&);  // _DISALLOW_ASSIGN

// Note, that most uses of CERES_DISALLOW_ASSIGN and CERES_DISALLOW_COPY
// are broken semantically, one should either use disallow both or
// neither. Try to avoid these in new code.
#define CERES_DISALLOW_COPY_AND_ASSIGN(TypeName) \
  TypeName(const TypeName&);               \
  void operator=(const TypeName&)

// A macro to disallow all the implicit constructors, namely the
// default constructor, copy constructor and operator= functions.
//
// This should be used in the private: declarations for a class
// that wants to prevent anyone from instantiating it. This is
// especially useful for classes containing only static methods.
#define CERES_DISALLOW_IMPLICIT_CONSTRUCTORS(TypeName) \
  TypeName();                                    \
  CERES_DISALLOW_COPY_AND_ASSIGN(TypeName)

// The arraysize(arr) macro returns the # of elements in an array arr.
// The expression is a compile-time constant, and therefore can be
// used in defining new arrays, for example.  If you use arraysize on
// a pointer by mistake, you will get a compile-time error.
//
// One caveat is that arraysize() doesn't accept any array of an
// anonymous type or a type defined inside a function.  In these rare
// cases, you have to use the unsafe ARRAYSIZE() macro below.  This is
// due to a limitation in C++'s template system.  The limitation might
// eventually be removed, but it hasn't happened yet.

// This template function declaration is used in defining arraysize.
// Note that the function doesn't need an implementation, as we only
// use its type.
template <typename T, size_t N>
char (&ArraySizeHelper(T (&array)[N]))[N];

// That gcc wants both of these prototypes seems mysterious. VC, for
// its part, can't decide which to use (another mystery). Matching of
// template overloads: the final frontier.
#ifndef _WIN32
template <typename T, size_t N>
char (&ArraySizeHelper(const T (&array)[N]))[N];
#endif

#define arraysize(array) (sizeof(ArraySizeHelper(array)))

// ARRAYSIZE performs essentially the same calculation as arraysize,
// but can be used on anonymous types or types defined inside
// functions.  It's less safe than arraysize as it accepts some
// (although not all) pointers.  Therefore, you should use arraysize
// whenever possible.
//
// The expression ARRAYSIZE(a) is a compile-time constant of type
// size_t.
//
// ARRAYSIZE catches a few type errors.  If you see a compiler error
//
//   "warning: division by zero in ..."
//
// when using ARRAYSIZE, you are (wrongfully) giving it a pointer.
// You should only use ARRAYSIZE on statically allocated arrays.
//
// The following comments are on the implementation details, and can
// be ignored by the users.
//
// ARRAYSIZE(arr) works by inspecting sizeof(arr) (the # of bytes in
// the array) and sizeof(*(arr)) (the # of bytes in one array
// element).  If the former is divisible by the latter, perhaps arr is
// indeed an array, in which case the division result is the # of
// elements in the array.  Otherwise, arr cannot possibly be an array,
// and we generate a compiler error to prevent the code from
// compiling.
//
// Since the size of bool is implementation-defined, we need to cast
// !(sizeof(a) & sizeof(*(a))) to size_t in order to ensure the final
// result has type size_t.
//
// This macro is not perfect as it wrongfully accepts certain
// pointers, namely where the pointer size is divisible by the pointee
// size.  Since all our code has to go through a 32-bit compiler,
// where a pointer is 4 bytes, this means all pointers to a type whose
// size is 3 or greater than 4 will be (righteously) rejected.
//
// Kudos to Jorg Brown for this simple and elegant implementation.
//
// - wan 2005-11-16
//
// Starting with Visual C++ 2005, WinNT.h includes ARRAYSIZE. However,
// the definition comes from the over-broad windows.h header that
// introduces a macro, ERROR, that conflicts with the logging framework
// that Ceres uses. Instead, rename ARRAYSIZE to CERES_ARRAYSIZE.
#define CERES_ARRAYSIZE(a)                              \
  ((sizeof(a) / sizeof(*(a))) /                         \
   static_cast<size_t>(!(sizeof(a) % sizeof(*(a)))))

// Tell the compiler to warn about unused return values for functions
// declared with this macro.  The macro should be used on function
// declarations following the argument list:
//
//   Sprocket* AllocateSprocket() MUST_USE_RESULT;
//
#if (__GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)) \
  && !defined(COMPILER_ICC)
#define CERES_MUST_USE_RESULT __attribute__ ((warn_unused_result))
#else
#define CERES_MUST_USE_RESULT
#endif

// Platform independent macros to get aligned memory allocations.
// For example
//
//   MyFoo my_foo CERES_ALIGN_ATTRIBUTE(16);
//
// Gives us an instance of MyFoo which is aligned at a 16 byte
// boundary.
#if defined(_MSC_VER)
#define CERES_ALIGN_ATTRIBUTE(n) __declspec(align(n))
#define CERES_ALIGN_OF(T) __alignof(T)
#elif defined(__GNUC__)
#define CERES_ALIGN_ATTRIBUTE(n) __attribute__((aligned(n)))
#define CERES_ALIGN_OF(T) __alignof(T)
#endif

#endif  // CERES_PUBLIC_INTERNAL_MACROS_H_