kkm000 · March 2, 2019 09:38 · kkm000 · Mar 2, 2019
diff --git a/logs-shoots-and-leaves.cc b/logs-shoots-and-leaves.cc
 /* logs-shoots-and-leaves.cc.

 One-liner test in bash:

 set -x; for cxx in g++-6 g++-7 g++-8 clang++-6.0 clang++-7; do \
 for std in 11 14 17; do \
  for endl in 0 1; do \
   $cxx -std=c++${std} -g -fdiagnostics-color \
        -Wall -Wextra -Wpedantic -rdynamic \
        -DTEST_ENDL=$endl -DHAVE_CXXABI_H -DHAVE_EXECINFO_H \
        logs-shoots-and-leaves.cc -o test && \
   ./test; \
 done; done; done; set +x

 */
 #include <cstdio>
 #include <cstring>

 #include <sstream>
 #include <stdexcept>
 #include <string>
 #include <vector>

 // Not in kaldi-error.{cc.h}:
 #include <iostream>
 #include <typeinfo>
 typedef int32_t int32;
 #define KALDI_VERSION "1.2.3.4"
 //---

 #ifdef _MSC_VER
 #define __func__ __FUNCTION__
 #endif

 #ifdef HAVE_EXECINFO_H
 #include <execinfo.h>  // To get stack trace in error messages.
 // If this #include fails there is an error in the Makefile, it does not
 // support your platform well. Make sure HAVE_EXECINFO_H is undefined,
 // and the code will compile.
 #ifdef HAVE_CXXABI_H
 #include <cxxabi.h>  // For name demangling.
 // Useful to decode the stack trace, but only used if we have execinfo.h
 #endif  // HAVE_CXXABI_H
 #endif  // HAVE_EXECINFO_H


 namespace kaldi {

 /// \addtogroup error_group
 /// @{

 /***** VERBOSITY LEVEL *****/

 /// This is set by util/parse-options.{h, cc} if you set --verbose=? option.
 extern int32 g_kaldi_verbose_level;

 /// This is set by util/parse-options.{h, cc} (from argv[0]) and used (if set)
 /// in error reporting code to display the name of the program (this is because
 /// in our scripts, we often mix together the stderr of many programs).  It is
 /// the base-name of the program (no directory).
 extern std::string g_program_name;

 inline int32 GetVerboseLevel() { return g_kaldi_verbose_level; }

 /// This should be rarely used; command-line programs set the verbosity level
 /// automatically from ParseOptions.
 inline void SetVerboseLevel(int32 i) { g_kaldi_verbose_level = i; }


 /***** KALDI LOGGING *****/

 /// Log message severity and source location info.
 struct LogMessageEnvelope {
  enum Severity {
    kAssertFailed = -3,
    kError = -2,
    kWarning = -1,
    kInfo = 0,
  };
  // An 'enum Severity' value, or a positive number indicating verbosity level.
  int severity;
  const char *func;
  const char *file;
  int32 line;
 };

 /// Kaldi runtime error exception. Thrown from any use of KALDI_ERR.
 class KaldiFatalError : public std::runtime_error {
 public:
  explicit KaldiFatalError(const std::string &message)
      : std::runtime_error(message) { }
  explicit KaldiFatalError(const char *message)
      : std::runtime_error(message) { }

  //TODO(kkm): Temporary(?) hack. Do we really need it? I think a better
  // approach to avoid double-logging the message is catch the KaldiFatalError
  // in binaries explicitly (and print nothing).
  virtual const char *what() const noexcept override { return ""; }

  const char *KaldiMessage() const { return std::runtime_error::what(); }
 };


 // Class MessageLogger is invoked from the KALDI_ASSERT, KALDI_ERR, KALDI_WARN
 // and KALDI_LOG macros. It formats the message, then either prints it to stderr
 // or passes to the custom logging handler if provided, then, in case of the
 // error, throws a KaldiErrorException, or in case of failed KALDI_ASSERT
 // calls std::terminate().
 //
 // Note: we do not use std::cerr because it allows output from threads to
 // interleave. fprintf(), on the other hand, outputs its formatted string
 // atomically.
 class MessageLogger {
 public:
  /// The constructor stores the message's "envelope", a set of data which
  /// identifies the location in source which is sending the message to log.
  /// The pointers to strings are stored internally, and not owned or copied,
  /// so that their storage must outlive this object.
  MessageLogger(LogMessageEnvelope::Severity severity,
                const char *func,
                const char *file,
                int32 line);

  /// The stream insertion operator, used in e.g. 'KALDI_LOG << "Message"'.
  template <typename T>
  MessageLogger &operator<<(const T &val) {
    ss_ << val;
    return *this;
  }

 #if TEST_ENDL
  /// The stream insertion operator for manipulators, e.g. 'KALDI_LOG << endl'.
  /// #### I DO NOT LIKE IT! Remove all uses of the endl() instead.
  MessageLogger& operator<<(std::ostream &(*val)(std::ostream &)) {
    ss_ << val;
    return *this;
  }
 #endif

  /// When assigned a MessageLogger, log its contents.
  struct Log final {
    void operator=(const MessageLogger& logger) {
      logger.LogMessage();
    }
  };

  /// When assigned a MessageLogger, log its contents and then throw
  /// a KaldiFatalError.
  struct LogAndThrow final {
    [[ noreturn ]] void operator=(const MessageLogger& logger) {
      logger.LogMessage();
      throw KaldiFatalError(logger.GetMessage());
    }
  };

 private:
  std::string GetMessage() const;
  void LogMessage() const;

  LogMessageEnvelope envelope_;
  std::ostringstream ss_;
 };

 // Logging macros.
 #define KALDI_ERR \
  ::kaldi::MessageLogger::LogAndThrow() = \
   ::kaldi::MessageLogger(::kaldi::LogMessageEnvelope::kError, \
                          __func__, __FILE__, __LINE__)
 #define KALDI_WARN \
  ::kaldi::MessageLogger::Log() = \
    ::kaldi::MessageLogger(::kaldi::LogMessageEnvelope::kWarning, \
                           __func__, __FILE__, __LINE__)
 #define KALDI_LOG \
  ::kaldi::MessageLogger::Log() = \
    ::kaldi::MessageLogger(::kaldi::LogMessageEnvelope::kInfo, \
                           __func__, __FILE__, __LINE__)
 #define KALDI_VLOG(v) \
  if ((v) <= ::kaldi::g_kaldi_verbose_level) \
    ::kaldi::MessageLogger::Log() = \
      ::kaldi::MessageLogger((::kaldi::LogMessageEnvelope::Severity)(v), \
                             __func__, __FILE__, __LINE__)

 /***** KALDI ASSERTS *****/

 [[ noreturn ]] void KaldiAssertFailure_(const char *func, const char *file,
                                        int32 line, const char *cond_str);

 // Note on KALDI_ASSERT and KALDI_PARANOID_ASSERT.
 // The original (simple) version of the code was this
 //
 // #define KALDI_ASSERT(cond) if (!(cond))
 //              kaldi::KaldiAssertFailure_(__func__, __FILE__, __LINE__, #cond);
 //
 // That worked well, but we were concerned that it could potentially cause a
 // performance issue due to failed branch prediction (best practice is to have
 // the if branch be the commonly taken one).
 //
 // Therefore, we decided to move the call into the else{} branch. A single block
 // {} around if/else does not work, because it causes syntax error (unmatched
 // else block) in the following code:
 //
 // if (condition)
 //   KALDI_ASSERT(condition2);
 // else
 //   SomethingElse();
 //
 // do {} while(0) -- note there is no semicolon at the end! -- works nicely,
 // and compilers will be able to optimize the loop away (as the condition is
 // always false).
 //
 // Also see KALDI_COMPILE_TIME_ASSERT, defined in base/kaldi-utils.h, and
 // KALDI_ASSERT_IS_INTEGER_TYPE and KALDI_ASSERT_IS_FLOATING_TYPE, also defined
 // there.
 #ifndef NDEBUG
 #define KALDI_ASSERT(cond) do { if (cond) (void)0; else \
  ::kaldi::KaldiAssertFailure_(__func__, __FILE__, __LINE__, #cond); } while(0)
 #else
 #define KALDI_ASSERT(cond) (void)0
 #endif

 // Some more expensive asserts only checked if this defined
 #ifdef KALDI_PARANOID
 #define KALDI_PARANOID_ASSERT(cond) do { if (cond) (void)0; else \
  ::kaldi::KaldiAssertFailure_(__func__, __FILE__, __LINE__, #cond); } while(0)
 #else
 #define KALDI_PARANOID_ASSERT(cond) (void)0
 #endif


 /***** THIRD-PARTY LOG-HANDLER *****/

 /// Type of third-party logging function.
 typedef void (*LogHandler)(const LogMessageEnvelope &envelope,
                           const char *message);

 /// Set logging handler. If called with a non-NULL function pointer, the
 /// function pointed by it is called to send messages to a caller-provided log.
 /// If called with a NULL pointer, restores default Kaldi error logging to
 /// stderr. SetLogHandler is obviously not thread safe; the log handler must be.
 LogHandler SetLogHandler(LogHandler);

 /// @} end "addtogroup error_group"

 /***** GLOBAL VARIABLES FOR LOGGING *****/

 int32 g_kaldi_verbose_level = 0;
 std::string g_program_name;
 static LogHandler g_log_handler = NULL;

 /***** HELPER FUNCTIONS *****/

 // Trim filename to at most 1 trailing directory long. Given a filename like
 // "/a/b/c/d/e/f.cc", return "e/f.cc". Support both '/' and '\' as the path
 // separator.
 static const char *GetShortFileName(const char *path) {
  if (path == nullptr)
    return "";

  const char *prev = path, *last = path;
  while ((path = std::strpbrk(path, "\\/")) != nullptr) {
    ++path;
    prev = last;
    last = path;
  }
  return prev;
 }


 /***** STACKTRACE *****/

 #ifdef HAVE_EXECINFO_H
 static std::string Demangle(std::string trace_name) {
 #ifdef HAVE_CXXABI_H
  // At input the string looks like:
  //   ./kaldi-error-test(_ZN5kaldi13UnitTestErrorEv+0xb) [0x804965d]
  // We want to extract the name e.g. '_ZN5kaldi13UnitTestErrorEv"
  // and demangle it.

  // Try to locate '(' and '+', take the string in between.
  size_t begin(trace_name.find("(")),
    end(trace_name.rfind("+"));
  if (begin != std::string::npos && end != std::string::npos && begin < end) {
    trace_name = trace_name.substr(begin + 1, end - (begin + 1));
  }
  // Try to demangle function name.
  int status;
  char *demangled_name = abi::__cxa_demangle(trace_name.c_str(), 0, 0, &status);
  if (status == 0) {
    trace_name = demangled_name;
    free(demangled_name);
  }
 #endif  // HAVE_CXXABI_H
  return trace_name;
 }
 #endif  // HAVE_EXECINFO_H


 static std::string KaldiGetStackTrace() {
  std::string ans;
 #ifdef HAVE_EXECINFO_H
  const size_t KALDI_MAX_TRACE_SIZE = 50;
  const size_t KALDI_MAX_TRACE_PRINT = 20;  // Must be even.
  // Buffer for the trace.
  void *trace[KALDI_MAX_TRACE_SIZE];
  // Get the trace.
  size_t size = backtrace(trace, KALDI_MAX_TRACE_SIZE);
  // Get the trace symbols.
  char **trace_symbol = backtrace_symbols(trace, size);
  if (trace_symbol == NULL)
    return ans;

  // Compose a human-readable backtrace string.
  ans += "[ Stack-Trace: ]\n";
  if (size <= KALDI_MAX_TRACE_PRINT) {
    for (size_t i = 0; i < size; i++) {
      ans += Demangle(trace_symbol[i]) + "\n";
    }
  } else {  // Print out first+last (e.g.) 5.
    for (size_t i = 0; i < KALDI_MAX_TRACE_PRINT/2; i++) {
      ans += Demangle(trace_symbol[i]) + "\n";
    }
    ans += ".\n.\n.\n";
    for (size_t i = size - KALDI_MAX_TRACE_PRINT/2; i < size; i++) {
      ans += Demangle(trace_symbol[i]) + "\n";
    }
    if (size == KALDI_MAX_TRACE_SIZE)
      ans += ".\n.\n.\n";  // Stack was too long, probably a bug.
  }

  // We must free the array of pointers allocated by backtrace_symbols(),
  // but not the strings themselves.
  free(trace_symbol);
 #endif  // HAVE_EXECINFO_H
  return ans;
 }


 /***** KALDI LOGGING *****/

 MessageLogger::MessageLogger(LogMessageEnvelope::Severity severity,
                             const char *func, const char *file, int32 line) {
  // Obviously, we assume the strings survive the destruction of this object.
  envelope_.severity = severity;
  envelope_.func = func;
  envelope_.file = GetShortFileName(file);  // Points inside 'file'.
  envelope_.line = line;
 }

 std::string MessageLogger::GetMessage() const {
  std::string str = ss_.str();

  // Remove any number of trailing linefeeds.
  // #### UGH!!!
  while (!str.empty() && (str[str.length() - 1] == '\n'))
    str.resize(str.length() - 1);

  return str;
 }

 void MessageLogger::LogMessage() const {
  std::string message = GetMessage();

  // Send to a logging handler if provided.
  if (g_log_handler != NULL) {
    g_log_handler(envelope_, message.c_str());
    return;
  }

  // Otherwise, use the default Kaldi logging.
  // Build the log-message header.
  std::stringstream header;
  if (envelope_.severity > LogMessageEnvelope::kInfo) {
    header << "VLOG[" << envelope_.severity << "] (";
  } else {
    switch (envelope_.severity) {
    case LogMessageEnvelope::kInfo :
      header << "LOG (";
      break;
    case LogMessageEnvelope::kWarning :
      header << "WARNING (";
      break;
    case LogMessageEnvelope::kAssertFailed :
      header << "ASSERTION_FAILED (";
      break;
    case LogMessageEnvelope::kError :
    default:  // If not the ERROR, it still an error!
      header << "ERROR (";
      break;
    }
  }
  // Fill other info from the envelope.
  header << g_program_name.c_str() << "[" KALDI_VERSION "]" << ':'
         << envelope_.func  << "():" << envelope_.file << ':'
         << envelope_.line << ")";

  // Add stack trace for errors and assertion failures, if available.
  if (envelope_.severity < LogMessageEnvelope::kWarning) {
    std::string stack_trace = KaldiGetStackTrace();
    if (!stack_trace.empty()) {
      message.append("\n\n");
      message.append(stack_trace);
    }
  }

  // Print the complete message to stderr.
  fprintf(stderr, "%s %s\n", header.str().c_str(), message.c_str());
 }

 /***** KALDI ASSERTS *****/

 void KaldiAssertFailure_(const char *func, const char *file,
                         int32 line, const char *cond_str) {
  MessageLogger::Log() =
    MessageLogger (LogMessageEnvelope::kAssertFailed, func, file, line)
      << "Assertion '" << cond_str << "' failed";
  fflush(NULL);
  std::abort();
 }


 /***** THIRD-PARTY LOG-HANDLER *****/

 LogHandler SetLogHandler(LogHandler handler) {
  LogHandler old_handler = g_log_handler;
  g_log_handler = handler;
  return old_handler;
 }

 }  // namespace kaldi


 // A custom inserter.

 struct Nnet {
 };

 class NnetComputation {
 public:
  void Print(std::ostream& os, const Nnet&) const {
    os << "[NnetComputation]";
  }
 };

 struct NnetComputationPrintInserter {
  const NnetComputation &computation;
  const Nnet &nnet;
  void Print(std::ostream &os) const { computation.Print(os, nnet); }
  friend std::ostream &operator<<(std::ostream &os,
                                  NnetComputationPrintInserter xhis) {
    xhis.Print(os);
    return os;
  }
 };

 double foo(const std::string& s) {
  int i = 42;
  double pi = 3.1415926;
  Nnet nnet;
  NnetComputation nnet_comp;

  KALDI_WARN << "Number=" << i
    << ", float=" << pi
    << ", hex=0x" << std::hex << i
    << ", boolean='" << std::boolalpha << (i == 42) << '\''
    << ", strings '" << s << "' and '" << s.c_str() << "'. "
 #if TEST_ENDL
    << std::endl
 #endif
    << "Custom inserter: " << NnetComputationPrintInserter{nnet_comp, nnet}
 #if TEST_ENDL
    << std::endl << std::endl
 #endif
    ;

  KALDI_ERR << "Number=" << i
    << ", float=" << pi
    << ", hex=0x" << std::hex << i
    << ", boolean='" << std::boolalpha << (i == 42) << '\''
    << ", strings '" << s << "' and '" << s.c_str() << "'. "
 #if TEST_ENDL
    << std::endl
 #endif
    << "Custom inserter: " << NnetComputationPrintInserter{nnet_comp, nnet}
 #if TEST_ENDL
    << std::endl << std::endl
 #endif
    ;

  // No return, no compliant.
 }

 int main () {
  try {
    foo("jabberwhacky");
    printf("*** foo() unexpectedly returned\n");
  } catch (const kaldi::KaldiFatalError& e) {
    printf("Calling foo(), caught KaldiFatalError, what()=\"%s\", message=\"%s\"\n",
           e.what(), e.KaldiMessage());
  } catch (const std::exception& e) {
    printf("*** This is unexpected. "
           "Calling foo(), caught '%s', what()=\"%s\"\n",
           typeid(e).name(), e.what());
  }

  int i = 42;
  try {
    KALDI_ASSERT(i > 42);
    printf("*** KALDI_ASSERT() unexpectedly returned!\n");
  } catch (const std::exception &e) {
    printf("*** KALDI_ASSERT() should have aborted! "
           "Caught '%s', what()=\"%s\"\n",
           typeid(e).name(), e.what());
  }

  return 0;
 }
	/* logs-shoots-and-leaves.cc.

	One-liner test in bash:

	set -x; for cxx in g++-6 g++-7 g++-8 clang++-6.0 clang++-7; do \
	for std in 11 14 17; do \
	for endl in 0 1; do \
	$cxx -std=c++${std} -g -fdiagnostics-color \
	-Wall -Wextra -Wpedantic -rdynamic \
	-DTEST_ENDL=$endl -DHAVE_CXXABI_H -DHAVE_EXECINFO_H \
	logs-shoots-and-leaves.cc -o test && \
	./test; \
	done; done; done; set +x

	*/
	#include <cstdio>
	#include <cstring>

	#include <sstream>
	#include <stdexcept>
	#include <string>
	#include <vector>

	// Not in kaldi-error.{cc.h}:
	#include <iostream>
	#include <typeinfo>
	typedef int32_t int32;
	#define KALDI_VERSION "1.2.3.4"
	//---

	#ifdef _MSC_VER
	#define __func__ __FUNCTION__
	#endif

	#ifdef HAVE_EXECINFO_H
	#include <execinfo.h> // To get stack trace in error messages.
	// If this #include fails there is an error in the Makefile, it does not
	// support your platform well. Make sure HAVE_EXECINFO_H is undefined,
	// and the code will compile.
	#ifdef HAVE_CXXABI_H
	#include <cxxabi.h> // For name demangling.
	// Useful to decode the stack trace, but only used if we have execinfo.h
	#endif // HAVE_CXXABI_H
	#endif // HAVE_EXECINFO_H


	namespace kaldi {

	/// \addtogroup error_group
	/// @{

	/*** VERBOSITY LEVEL ***/

	/// This is set by util/parse-options.{h, cc} if you set --verbose=? option.
	extern int32 g_kaldi_verbose_level;

	/// This is set by util/parse-options.{h, cc} (from argv[0]) and used (if set)
	/// in error reporting code to display the name of the program (this is because
	/// in our scripts, we often mix together the stderr of many programs). It is
	/// the base-name of the program (no directory).
	extern std::string g_program_name;

	inline int32 GetVerboseLevel() { return g_kaldi_verbose_level; }

	/// This should be rarely used; command-line programs set the verbosity level
	/// automatically from ParseOptions.
	inline void SetVerboseLevel(int32 i) { g_kaldi_verbose_level = i; }


	/*** KALDI LOGGING ***/

	/// Log message severity and source location info.
	struct LogMessageEnvelope {
	enum Severity {
	kAssertFailed = -3,
	kError = -2,
	kWarning = -1,
	kInfo = 0,
	};
	// An 'enum Severity' value, or a positive number indicating verbosity level.
	int severity;
	const char *func;
	const char *file;
	int32 line;
	};

	/// Kaldi runtime error exception. Thrown from any use of KALDI_ERR.
	class KaldiFatalError : public std::runtime_error {
	public:
	explicit KaldiFatalError(const std::string &message)
	: std::runtime_error(message) { }
	explicit KaldiFatalError(const char *message)
	: std::runtime_error(message) { }

	//TODO(kkm): Temporary(?) hack. Do we really need it? I think a better
	// approach to avoid double-logging the message is catch the KaldiFatalError
	// in binaries explicitly (and print nothing).
	virtual const char *what() const noexcept override { return ""; }

	const char *KaldiMessage() const { return std::runtime_error::what(); }
	};


	// Class MessageLogger is invoked from the KALDI_ASSERT, KALDI_ERR, KALDI_WARN
	// and KALDI_LOG macros. It formats the message, then either prints it to stderr
	// or passes to the custom logging handler if provided, then, in case of the
	// error, throws a KaldiErrorException, or in case of failed KALDI_ASSERT
	// calls std::terminate().
	//
	// Note: we do not use std::cerr because it allows output from threads to
	// interleave. fprintf(), on the other hand, outputs its formatted string
	// atomically.
	class MessageLogger {
	public:
	/// The constructor stores the message's "envelope", a set of data which
	/// identifies the location in source which is sending the message to log.
	/// The pointers to strings are stored internally, and not owned or copied,
	/// so that their storage must outlive this object.
	MessageLogger(LogMessageEnvelope::Severity severity,
	const char *func,
	const char *file,
	int32 line);

	/// The stream insertion operator, used in e.g. 'KALDI_LOG << "Message"'.
	template <typename T>
	MessageLogger &operator<<(const T &val) {
	ss_ << val;
	return *this;
	}

	#if TEST_ENDL
	/// The stream insertion operator for manipulators, e.g. 'KALDI_LOG << endl'.
	/// #### I DO NOT LIKE IT! Remove all uses of the endl() instead.
	MessageLogger& operator<<(std::ostream &(*val)(std::ostream &)) {
	ss_ << val;
	return *this;
	}
	#endif

	/// When assigned a MessageLogger, log its contents.
	struct Log final {
	void operator=(const MessageLogger& logger) {
	logger.LogMessage();
	}
	};

	/// When assigned a MessageLogger, log its contents and then throw
	/// a KaldiFatalError.
	struct LogAndThrow final {
	[[ noreturn ]] void operator=(const MessageLogger& logger) {
	logger.LogMessage();
	throw KaldiFatalError(logger.GetMessage());
	}
	};

	private:
	std::string GetMessage() const;
	void LogMessage() const;

	LogMessageEnvelope envelope_;
	std::ostringstream ss_;
	};

	// Logging macros.
	#define KALDI_ERR \
	::kaldi::MessageLogger::LogAndThrow() = \
	::kaldi::MessageLogger(::kaldi::LogMessageEnvelope::kError, \
	__func__, __FILE__, __LINE__)
	#define KALDI_WARN \
	::kaldi::MessageLogger::Log() = \
	::kaldi::MessageLogger(::kaldi::LogMessageEnvelope::kWarning, \
	__func__, __FILE__, __LINE__)
	#define KALDI_LOG \
	::kaldi::MessageLogger::Log() = \
	::kaldi::MessageLogger(::kaldi::LogMessageEnvelope::kInfo, \
	__func__, __FILE__, __LINE__)
	#define KALDI_VLOG(v) \
	if ((v) <= ::kaldi::g_kaldi_verbose_level) \
	::kaldi::MessageLogger::Log() = \
	::kaldi::MessageLogger((::kaldi::LogMessageEnvelope::Severity)(v), \
	__func__, __FILE__, __LINE__)

	/*** KALDI ASSERTS ***/

	[[ noreturn ]] void KaldiAssertFailure_(const char func, const char file,
	int32 line, const char *cond_str);

	// Note on KALDI_ASSERT and KALDI_PARANOID_ASSERT.
	// The original (simple) version of the code was this
	//
	// #define KALDI_ASSERT(cond) if (!(cond))
	// kaldi::KaldiAssertFailure_(__func__, __FILE__, __LINE__, #cond);
	//
	// That worked well, but we were concerned that it could potentially cause a
	// performance issue due to failed branch prediction (best practice is to have
	// the if branch be the commonly taken one).
	//
	// Therefore, we decided to move the call into the else{} branch. A single block
	// {} around if/else does not work, because it causes syntax error (unmatched
	// else block) in the following code:
	//
	// if (condition)
	// KALDI_ASSERT(condition2);
	// else
	// SomethingElse();
	//
	// do {} while(0) -- note there is no semicolon at the end! -- works nicely,
	// and compilers will be able to optimize the loop away (as the condition is
	// always false).
	//
	// Also see KALDI_COMPILE_TIME_ASSERT, defined in base/kaldi-utils.h, and
	// KALDI_ASSERT_IS_INTEGER_TYPE and KALDI_ASSERT_IS_FLOATING_TYPE, also defined
	// there.
	#ifndef NDEBUG
	#define KALDI_ASSERT(cond) do { if (cond) (void)0; else \
	::kaldi::KaldiAssertFailure_(__func__, __FILE__, __LINE__, #cond); } while(0)
	#else
	#define KALDI_ASSERT(cond) (void)0
	#endif

	// Some more expensive asserts only checked if this defined
	#ifdef KALDI_PARANOID
	#define KALDI_PARANOID_ASSERT(cond) do { if (cond) (void)0; else \
	::kaldi::KaldiAssertFailure_(__func__, __FILE__, __LINE__, #cond); } while(0)
	#else
	#define KALDI_PARANOID_ASSERT(cond) (void)0
	#endif


	/*** THIRD-PARTY LOG-HANDLER ***/

	/// Type of third-party logging function.
	typedef void (*LogHandler)(const LogMessageEnvelope &envelope,
	const char *message);

	/// Set logging handler. If called with a non-NULL function pointer, the
	/// function pointed by it is called to send messages to a caller-provided log.
	/// If called with a NULL pointer, restores default Kaldi error logging to
	/// stderr. SetLogHandler is obviously not thread safe; the log handler must be.
	LogHandler SetLogHandler(LogHandler);

	/// @} end "addtogroup error_group"

	/*** GLOBAL VARIABLES FOR LOGGING ***/

	int32 g_kaldi_verbose_level = 0;
	std::string g_program_name;
	static LogHandler g_log_handler = NULL;

	/*** HELPER FUNCTIONS ***/

	// Trim filename to at most 1 trailing directory long. Given a filename like
	// "/a/b/c/d/e/f.cc", return "e/f.cc". Support both '/' and '\' as the path
	// separator.
	static const char GetShortFileName(const char path) {
	if (path == nullptr)
	return "";

	const char prev = path, last = path;
	while ((path = std::strpbrk(path, "\\/")) != nullptr) {
	++path;
	prev = last;
	last = path;
	}
	return prev;
	}


	/*** STACKTRACE ***/

	#ifdef HAVE_EXECINFO_H
	static std::string Demangle(std::string trace_name) {
	#ifdef HAVE_CXXABI_H
	// At input the string looks like:
	// ./kaldi-error-test(_ZN5kaldi13UnitTestErrorEv+0xb) [0x804965d]
	// We want to extract the name e.g. '_ZN5kaldi13UnitTestErrorEv"
	// and demangle it.

	// Try to locate '(' and '+', take the string in between.
	size_t begin(trace_name.find("(")),
	end(trace_name.rfind("+"));
	if (begin != std::string::npos && end != std::string::npos && begin < end) {
	trace_name = trace_name.substr(begin + 1, end - (begin + 1));
	}
	// Try to demangle function name.
	int status;
	char *demangled_name = abi::__cxa_demangle(trace_name.c_str(), 0, 0, &status);
	if (status == 0) {
	trace_name = demangled_name;
	free(demangled_name);
	}
	#endif // HAVE_CXXABI_H
	return trace_name;
	}
	#endif // HAVE_EXECINFO_H


	static std::string KaldiGetStackTrace() {
	std::string ans;
	#ifdef HAVE_EXECINFO_H
	const size_t KALDI_MAX_TRACE_SIZE = 50;
	const size_t KALDI_MAX_TRACE_PRINT = 20; // Must be even.
	// Buffer for the trace.
	void *trace[KALDI_MAX_TRACE_SIZE];
	// Get the trace.
	size_t size = backtrace(trace, KALDI_MAX_TRACE_SIZE);
	// Get the trace symbols.
	char **trace_symbol = backtrace_symbols(trace, size);
	if (trace_symbol == NULL)
	return ans;

	// Compose a human-readable backtrace string.
	ans += "[ Stack-Trace: ]\n";
	if (size <= KALDI_MAX_TRACE_PRINT) {
	for (size_t i = 0; i < size; i++) {
	ans += Demangle(trace_symbol[i]) + "\n";
	}
	} else { // Print out first+last (e.g.) 5.
	for (size_t i = 0; i < KALDI_MAX_TRACE_PRINT/2; i++) {
	ans += Demangle(trace_symbol[i]) + "\n";
	}
	ans += ".\n.\n.\n";
	for (size_t i = size - KALDI_MAX_TRACE_PRINT/2; i < size; i++) {
	ans += Demangle(trace_symbol[i]) + "\n";
	}
	if (size == KALDI_MAX_TRACE_SIZE)
	ans += ".\n.\n.\n"; // Stack was too long, probably a bug.
	}

	// We must free the array of pointers allocated by backtrace_symbols(),
	// but not the strings themselves.
	free(trace_symbol);
	#endif // HAVE_EXECINFO_H
	return ans;
	}


	/*** KALDI LOGGING ***/

	MessageLogger::MessageLogger(LogMessageEnvelope::Severity severity,
	const char func, const char file, int32 line) {
	// Obviously, we assume the strings survive the destruction of this object.
	envelope_.severity = severity;
	envelope_.func = func;
	envelope_.file = GetShortFileName(file); // Points inside 'file'.
	envelope_.line = line;
	}

	std::string MessageLogger::GetMessage() const {
	std::string str = ss_.str();

	// Remove any number of trailing linefeeds.
	// #### UGH!!!
	while (!str.empty() && (str[str.length() - 1] == '\n'))
	str.resize(str.length() - 1);

	return str;
	}

	void MessageLogger::LogMessage() const {
	std::string message = GetMessage();

	// Send to a logging handler if provided.
	if (g_log_handler != NULL) {
	g_log_handler(envelope_, message.c_str());
	return;
	}

	// Otherwise, use the default Kaldi logging.
	// Build the log-message header.
	std::stringstream header;
	if (envelope_.severity > LogMessageEnvelope::kInfo) {
	header << "VLOG[" << envelope_.severity << "] (";
	} else {
	switch (envelope_.severity) {
	case LogMessageEnvelope::kInfo :
	header << "LOG (";
	break;
	case LogMessageEnvelope::kWarning :
	header << "WARNING (";
	break;
	case LogMessageEnvelope::kAssertFailed :
	header << "ASSERTION_FAILED (";
	break;
	case LogMessageEnvelope::kError :
	default: // If not the ERROR, it still an error!
	header << "ERROR (";
	break;
	}
	}
	// Fill other info from the envelope.
	header << g_program_name.c_str() << "[" KALDI_VERSION "]" << ':'
	<< envelope_.func << "():" << envelope_.file << ':'
	<< envelope_.line << ")";

	// Add stack trace for errors and assertion failures, if available.
	if (envelope_.severity < LogMessageEnvelope::kWarning) {
	std::string stack_trace = KaldiGetStackTrace();
	if (!stack_trace.empty()) {
	message.append("\n\n");
	message.append(stack_trace);
	}
	}

	// Print the complete message to stderr.
	fprintf(stderr, "%s %s\n", header.str().c_str(), message.c_str());
	}

	/*** KALDI ASSERTS ***/

	void KaldiAssertFailure_(const char func, const char file,
	int32 line, const char *cond_str) {
	MessageLogger::Log() =
	MessageLogger (LogMessageEnvelope::kAssertFailed, func, file, line)
	<< "Assertion '" << cond_str << "' failed";
	fflush(NULL);
	std::abort();
	}


	/*** THIRD-PARTY LOG-HANDLER ***/

	LogHandler SetLogHandler(LogHandler handler) {
	LogHandler old_handler = g_log_handler;
	g_log_handler = handler;
	return old_handler;
	}

	} // namespace kaldi


	// A custom inserter.

	struct Nnet {
	};

	class NnetComputation {
	public:
	void Print(std::ostream& os, const Nnet&) const {
	os << "[NnetComputation]";
	}
	};

	struct NnetComputationPrintInserter {
	const NnetComputation &computation;
	const Nnet &nnet;
	void Print(std::ostream &os) const { computation.Print(os, nnet); }
	friend std::ostream &operator<<(std::ostream &os,
	NnetComputationPrintInserter xhis) {
	xhis.Print(os);
	return os;
	}
	};

	double foo(const std::string& s) {
	int i = 42;
	double pi = 3.1415926;
	Nnet nnet;
	NnetComputation nnet_comp;

	KALDI_WARN << "Number=" << i
	<< ", float=" << pi
	<< ", hex=0x" << std::hex << i
	<< ", boolean='" << std::boolalpha << (i == 42) << '\''
	<< ", strings '" << s << "' and '" << s.c_str() << "'. "
	#if TEST_ENDL
	<< std::endl
	#endif
	<< "Custom inserter: " << NnetComputationPrintInserter{nnet_comp, nnet}
	#if TEST_ENDL
	<< std::endl << std::endl
	#endif
	;

	KALDI_ERR << "Number=" << i
	<< ", float=" << pi
	<< ", hex=0x" << std::hex << i
	<< ", boolean='" << std::boolalpha << (i == 42) << '\''
	<< ", strings '" << s << "' and '" << s.c_str() << "'. "
	#if TEST_ENDL
	<< std::endl
	#endif
	<< "Custom inserter: " << NnetComputationPrintInserter{nnet_comp, nnet}
	#if TEST_ENDL
	<< std::endl << std::endl
	#endif
	;

	// No return, no compliant.
	}

	int main () {
	try {
	foo("jabberwhacky");
	printf("*** foo() unexpectedly returned\n");
	} catch (const kaldi::KaldiFatalError& e) {
	printf("Calling foo(), caught KaldiFatalError, what()=\"%s\", message=\"%s\"\n",
	e.what(), e.KaldiMessage());
	} catch (const std::exception& e) {
	printf("*** This is unexpected. "
	"Calling foo(), caught '%s', what()=\"%s\"\n",
	typeid(e).name(), e.what());
	}

	int i = 42;
	try {
	KALDI_ASSERT(i > 42);
	printf("*** KALDI_ASSERT() unexpectedly returned!\n");
	} catch (const std::exception &e) {
	printf("*** KALDI_ASSERT() should have aborted! "
	"Caught '%s', what()=\"%s\"\n",
	typeid(e).name(), e.what());
	}

	return 0;
	}