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+/*********************                                                        */
+/*! \file cvc4_check.h
+ ** \verbatim
+ ** Top contributors (to current version):
+ **   Tim King
+ ** This file is part of the CVC4 project.
+ ** Copyright (c) 2009-2018 by the authors listed in the file AUTHORS
+ ** in the top-level source directory) and their institutional affiliations.
+ ** All rights reserved.  See the file COPYING in the top-level source
+ ** directory for licensing information.\endverbatim
+ **
+ ** \brief Assertion utility classes, functions and macros.
+ **
+ ** The CHECK utility classes, functions and macros are related to the Assert()
+ ** macros defined in base/cvc4_assert.h. The major distinguishing attribute
+ ** is the CHECK's abort() the process on failures while Assert() statements
+ ** throw C++ exceptions.
+ **
+ ** The main usage in the file is the CHECK macros. The CHECK macros assert a
+ ** condition and aborts()'s the process if the condition is not satisfied. The
+ ** macro leaves a hanging ostream for the user to specify additional
+ ** information about the failure. Example usage:
+ **   CHECK(x >= 0) << "x must be positive.";
+ **
+ ** DCHECK is a CHECK that is only enabled in debug builds.
+ **   DCHECK(pointer != nullptr);
+ **
+ ** CVC4_FATAL() can be used to indicate unreachable code.
+ **
+ ** The CHECK and DCHECK macros are not safe for use in signal-handling code.
+ ** TODO(taking): Add a signal-handling safe version of CHECK.
+ **/
+
+#include "cvc4_private.h"
+
+#ifndef __CVC4__CHECK_H
+#define __CVC4__CHECK_H
+
+#include <ostream>
+
+// Define CVC4_NO_RETURN macro replacement for [[noreturn]].
+#if defined(SWIG)
+#define CVC4_NO_RETURN
+// SWIG does not yet support [[noreturn]] so emit nothing instead.
+#else
+#define CVC4_NO_RETURN [[noreturn]]
+// Not checking for whether the compiler supports [[noreturn]] using
+// __has_cpp_attribute as GCC 4.8 is too widespread and does not support this.
+// We instead assume this is C++11 (or later) and [[noreturn]] is available.
+#endif  // defined(SWIG)
+
+// Define CVC4_PREDICT_FALSE(x) that helps the compiler predict that x will be
+// false (if there is compiler support).
+#ifdef __has_builtin
+#if __has_builtin(__builtin_expect)
+#define CVC4_PREDICT_FALSE(x) (__builtin_expect(x, false))
+#else
+#define CVC4_PREDICT_FALSE(x) x
+#endif
+#else
+#define CVC4_PREDICT_FALSE(x) x
+#endif
+
+namespace CVC4 {
+
+// Implementation notes:
+// To understand FatalStream and OStreamVoider, it is useful to understand
+// how a CHECK is structured. CHECK(cond) is roughly the following pattern:
+//  cond ? (void)0 : OstreamVoider() & FatalStream().stream()
+// This is a carefully crafted message to achieve a hanging ostream using
+// operator precedence. The line `CHECK(cond) << foo << bar;` will bind as
+// follows:
+//  `cond ? ((void)0) : (OSV() & ((FS().stream() << foo) << bar));`
+// Once the expression is evaluated, the destructor ~FatalStream() of the
+// temporary object is then run, which abort()'s the process. The role of the
+// OStreamVoider() is to match the void type of the true branch.
+
+// Class that provides an ostream and whose destructor aborts! Direct usage of
+// this class is discouraged.
+class FatalStream
+{
+ public:
+  FatalStream(const char* function, const char* file, int line);
+  CVC4_NO_RETURN ~FatalStream();
+
+  std::ostream& stream();
+
+ private:
+  void Flush();
+};
+
+// Helper class that changes the type of an std::ostream& into a void. See
+// "Implementation notes" for more information.
+class OstreamVoider
+{
+ public:
+  OstreamVoider() {}
+  // The operator precedence between operator& and operator<< is critical here.
+  void operator&(std::ostream&) {}
+};
+
+// CVC4_FATAL() always aborts a function and provides a convenient way of
+// formatting error messages. This can be used instead of a return type.
+//
+// Example function that returns a type Foo:
+//   Foo bar(T t) {
+//     switch(t.type()) {
+//     ...
+//     default:
+//       CVC4_FATAL() << "Unknown T type " << t.enum();
+//     }
+//   }
+#define CVC4_FATAL() \
+  FatalStream(__PRETTY_FUNCTION__, __FILE__, __LINE__).stream()
+
+// If `cond` is true, log an error message and abort the process.
+// Otherwise, does nothing. This leaves a hanging std::ostream& that can be
+// inserted into.
+#define CVC4_FATAL_IF(cond, function, file, line) \
+  CVC4_PREDICT_FALSE(!(cond))                     \
+  ? (void)0 : OstreamVoider() & FatalStream(function, file, line).stream()
+
+// If `cond` is false, log an error message and abort()'s the process.
+// Otherwise, does nothing. This leaves a hanging std::ostream& that can be
+// inserted into using operator<<. Example usages:
+//   CHECK(x >= 0);
+//   CHECK(x >= 0) << "x must be positive";
+//   CHECK(x >= 0) << "expected a positive value. Got " << x << " instead";
+#define CHECK(cond)                                               \
+  CVC4_FATAL_IF(!(cond), __PRETTY_FUNCTION__, __FILE__, __LINE__) \
+      << "Check failure\n\n " << #cond << "\n"
+
+// DCHECK is a variant of CHECK() that is only checked when CVC4_ASSERTIONS is
+// defined. We rely on the optimizer to remove the deadcode.
+#ifdef CVC4_ASSERTIONS
+#define DCHECK(cond) CHECK(cond)
+#else
+#define DCHECK(cond) \
+  CVC4_FATAL_IF(false, __PRETTY_FUNCTION__, __FILE__, __LINE__)
+#endif /* CVC4_DEBUG */
+
+}  // namespace CVC4
+
+#endif /* __CVC4__CHECK_H */