--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/CSP2/CSP2_env/env-d9b9114564458d9d-741b3de822f2aaca6c6caa4325c4afce/include/kj/debug.h	Tue Mar 18 17:55:14 2025 -0400
@@ -0,0 +1,737 @@
+// Copyright (c) 2013-2014 Sandstorm Development Group, Inc. and contributors
+// Licensed under the MIT License:
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+// This file declares convenient macros for debug logging and error handling.  The macros make
+// it excessively easy to extract useful context information from code.  Example:
+//
+//     KJ_ASSERT(a == b, a, b, "a and b must be the same.");
+//
+// On failure, this will throw an exception whose description looks like:
+//
+//     myfile.c++:43: bug in code: expected a == b; a = 14; b = 72; a and b must be the same.
+//
+// As you can see, all arguments after the first provide additional context.
+//
+// The macros available are:
+//
+// * `KJ_LOG(severity, ...)`:  Just writes a log message, to stderr by default (but you can
+//   intercept messages by implementing an ExceptionCallback).  `severity` is `INFO`, `WARNING`,
+//   `ERROR`, or `FATAL`.  By default, `INFO` logs are not written, but for command-line apps the
+//   user should be able to pass a flag like `--verbose` to enable them.  Other log levels are
+//   enabled by default.  Log messages -- like exceptions -- can be intercepted by registering an
+//   ExceptionCallback.
+//
+// * `KJ_DBG(...)`:  Like `KJ_LOG`, but intended specifically for temporary log lines added while
+//   debugging a particular problem.  Calls to `KJ_DBG` should always be deleted before committing
+//   code.  It is suggested that you set up a pre-commit hook that checks for this.
+//
+// * `KJ_ASSERT(condition, ...)`:  Throws an exception if `condition` is false, or aborts if
+//   exceptions are disabled.  This macro should be used to check for bugs in the surrounding code
+//   and its dependencies, but NOT to check for invalid input.  The macro may be followed by a
+//   brace-delimited code block; if so, the block will be executed in the case where the assertion
+//   fails, before throwing the exception.  If control jumps out of the block (e.g. with "break",
+//   "return", or "goto"), then the error is considered "recoverable" -- in this case, if
+//   exceptions are disabled, execution will continue normally rather than aborting (but if
+//   exceptions are enabled, an exception will still be thrown on exiting the block). A "break"
+//   statement in particular will jump to the code immediately after the block (it does not break
+//   any surrounding loop or switch).  Example:
+//
+//       KJ_ASSERT(value >= 0, "Value cannot be negative.", value) {
+//         // Assertion failed.  Set value to zero to "recover".
+//         value = 0;
+//         // Don't abort if exceptions are disabled.  Continue normally.
+//         // (Still throw an exception if they are enabled, though.)
+//         break;
+//       }
+//       // When exceptions are disabled, we'll get here even if the assertion fails.
+//       // Otherwise, we get here only if the assertion passes.
+//
+// * `KJ_REQUIRE(condition, ...)`:  Like `KJ_ASSERT` but used to check preconditions -- e.g. to
+//   validate parameters passed from a caller.  A failure indicates that the caller is buggy.
+//
+// * `KJ_ASSUME(condition, ...)`: Like `KJ_ASSERT`, but in release mode (if KJ_DEBUG is not
+//   defined; see below) instead warrants to the compiler that the condition can be assumed to
+//   hold, allowing it to optimize accordingly.  This can result in undefined behavior, so use
+//   this macro *only* if you can prove to your satisfaction that the condition is guaranteed by
+//   surrounding code, and if the condition failing to hold would in any case result in undefined
+//   behavior in its dependencies.
+//
+// * `KJ_SYSCALL(code, ...)`:  Executes `code` assuming it makes a system call.  A negative result
+//   is considered an error, with error code reported via `errno`.  EINTR is handled by retrying.
+//   Other errors are handled by throwing an exception.  If you need to examine the return code,
+//   assign it to a variable like so:
+//
+//       int fd;
+//       KJ_SYSCALL(fd = open(filename, O_RDONLY), filename);
+//
+//   `KJ_SYSCALL` can be followed by a recovery block, just like `KJ_ASSERT`.
+//
+// * `KJ_NONBLOCKING_SYSCALL(code, ...)`:  Like KJ_SYSCALL, but will not throw an exception on
+//   EAGAIN/EWOULDBLOCK.  The calling code should check the syscall's return value to see if it
+//   indicates an error; in this case, it can assume the error was EAGAIN because any other error
+//   would have caused an exception to be thrown.
+//
+// * `KJ_CONTEXT(...)`:  Notes additional contextual information relevant to any exceptions thrown
+//   from within the current scope.  That is, until control exits the block in which KJ_CONTEXT()
+//   is used, if any exception is generated, it will contain the given information in its context
+//   chain.  This is helpful because it can otherwise be very difficult to come up with error
+//   messages that make sense within low-level helper code.  Note that the parameters to
+//   KJ_CONTEXT() are only evaluated if an exception is thrown.  This implies that any variables
+//   used must remain valid until the end of the scope.
+//
+// Notes:
+// * Do not write expressions with side-effects in the message content part of the macro, as the
+//   message will not necessarily be evaluated.
+// * For every macro `FOO` above except `LOG`, there is also a `FAIL_FOO` macro used to report
+//   failures that already happened.  For the macros that check a boolean condition, `FAIL_FOO`
+//   omits the first parameter and behaves like it was `false`.  `FAIL_SYSCALL` and
+//   `FAIL_RECOVERABLE_SYSCALL` take a string and an OS error number as the first two parameters.
+//   The string should be the name of the failed system call.
+// * For every macro `FOO` above except `ASSUME`, there is a `DFOO` version (or
+//   `RECOVERABLE_DFOO`) which is only executed in debug mode, i.e. when KJ_DEBUG is defined.
+//   KJ_DEBUG is defined automatically by common.h when compiling without optimization (unless
+//   NDEBUG is defined), but you can also define it explicitly (e.g. -DKJ_DEBUG).  Generally,
+//   production builds should NOT use KJ_DEBUG as it may enable expensive checks that are unlikely
+//   to fail.
+
+#pragma once
+
+#include "string.h"
+#include "exception.h"
+#include "windows-sanity.h"  // work-around macro conflict with `ERROR`
+
+KJ_BEGIN_HEADER
+
+namespace kj {
+
+#if KJ_MSVC_TRADITIONAL_CPP
+// MSVC does __VA_ARGS__ differently from GCC:
+// - A trailing comma before an empty __VA_ARGS__ is removed automatically, whereas GCC wants
+//   you to request this behavior with "##__VA_ARGS__".
+// - If __VA_ARGS__ is passed directly as an argument to another macro, it will be treated as a
+//   *single* argument rather than an argument list. This can be worked around by wrapping the
+//   outer macro call in KJ_EXPAND(), which apparently forces __VA_ARGS__ to be expanded before
+//   the macro is evaluated. I don't understand the C preprocessor.
+// - Using "#__VA_ARGS__" to stringify __VA_ARGS__ expands to zero tokens when __VA_ARGS__ is
+//   empty, rather than expanding to an empty string literal. We can work around by concatenating
+//   with an empty string literal.
+
+#define KJ_EXPAND(X) X
+
+#define KJ_LOG(severity, ...) \
+  for (bool _kj_shouldLog = ::kj::_::Debug::shouldLog(::kj::LogSeverity::severity); \
+       _kj_shouldLog; _kj_shouldLog = false) \
+    ::kj::_::Debug::log(__FILE__, __LINE__, ::kj::LogSeverity::severity, \
+                        "" #__VA_ARGS__, __VA_ARGS__)
+
+#define KJ_DBG(...) KJ_EXPAND(KJ_LOG(DBG, __VA_ARGS__))
+
+#define KJ_REQUIRE(cond, ...) \
+  if (auto _kjCondition = ::kj::_::MAGIC_ASSERT << cond) {} else \
+    for (::kj::_::Debug::Fault f(__FILE__, __LINE__, ::kj::Exception::Type::FAILED, \
+        #cond, "_kjCondition," #__VA_ARGS__, _kjCondition, __VA_ARGS__);; f.fatal())
+
+#define KJ_FAIL_REQUIRE(...) \
+  for (::kj::_::Debug::Fault f(__FILE__, __LINE__, ::kj::Exception::Type::FAILED, \
+                               nullptr, "" #__VA_ARGS__, __VA_ARGS__);; f.fatal())
+
+#define KJ_SYSCALL(call, ...) \
+  if (auto _kjSyscallResult = ::kj::_::Debug::syscall([&](){return (call);}, false)) {} else \
+    for (::kj::_::Debug::Fault f(__FILE__, __LINE__, \
+             _kjSyscallResult.getErrorNumber(), #call, "" #__VA_ARGS__, __VA_ARGS__);; f.fatal())
+
+#define KJ_NONBLOCKING_SYSCALL(call, ...) \
+  if (auto _kjSyscallResult = ::kj::_::Debug::syscall([&](){return (call);}, true)) {} else \
+    for (::kj::_::Debug::Fault f(__FILE__, __LINE__, \
+             _kjSyscallResult.getErrorNumber(), #call, "" #__VA_ARGS__, __VA_ARGS__);; f.fatal())
+
+#define KJ_FAIL_SYSCALL(code, errorNumber, ...) \
+  for (::kj::_::Debug::Fault f(__FILE__, __LINE__, \
+           errorNumber, code, "" #__VA_ARGS__, __VA_ARGS__);; f.fatal())
+
+#if _WIN32 || __CYGWIN__
+
+#define KJ_WIN32(call, ...) \
+  if (auto _kjWin32Result = ::kj::_::Debug::win32Call(call)) {} else \
+    for (::kj::_::Debug::Fault f(__FILE__, __LINE__, \
+             _kjWin32Result, #call, "" #__VA_ARGS__, __VA_ARGS__);; f.fatal())
+
+#define KJ_WINSOCK(call, ...) \
+  if (auto _kjWin32Result = ::kj::_::Debug::winsockCall(call)) {} else \
+    for (::kj::_::Debug::Fault f(__FILE__, __LINE__, \
+             _kjWin32Result, #call, "" #__VA_ARGS__, __VA_ARGS__);; f.fatal())
+
+#define KJ_FAIL_WIN32(code, errorNumber, ...) \
+  for (::kj::_::Debug::Fault f(__FILE__, __LINE__, \
+           ::kj::_::Debug::Win32Result(errorNumber), code, "" #__VA_ARGS__, __VA_ARGS__);; f.fatal())
+
+#endif
+
+#define KJ_UNIMPLEMENTED(...) \
+  for (::kj::_::Debug::Fault f(__FILE__, __LINE__, ::kj::Exception::Type::UNIMPLEMENTED, \
+                               nullptr, "" #__VA_ARGS__, __VA_ARGS__);; f.fatal())
+
+// TODO(msvc):  MSVC mis-deduces `ContextImpl<decltype(func)>` as `ContextImpl<int>` in some edge
+// cases, such as inside nested lambdas inside member functions. Wrapping the type in
+// `decltype(instance<...>())` helps it deduce the context function's type correctly.
+#define KJ_CONTEXT(...) \
+  auto KJ_UNIQUE_NAME(_kjContextFunc) = [&]() -> ::kj::_::Debug::Context::Value { \
+        return ::kj::_::Debug::Context::Value(__FILE__, __LINE__, \
+            ::kj::_::Debug::makeDescription("" #__VA_ARGS__, __VA_ARGS__)); \
+      }; \
+  decltype(::kj::instance<::kj::_::Debug::ContextImpl<decltype(KJ_UNIQUE_NAME(_kjContextFunc))>>()) \
+      KJ_UNIQUE_NAME(_kjContext)(KJ_UNIQUE_NAME(_kjContextFunc))
+
+#define KJ_REQUIRE_NONNULL(value, ...) \
+  (*[&] { \
+    auto _kj_result = ::kj::_::readMaybe(value); \
+    if (KJ_UNLIKELY(!_kj_result)) { \
+      ::kj::_::Debug::Fault(__FILE__, __LINE__, ::kj::Exception::Type::FAILED, \
+                            #value " != nullptr", "" #__VA_ARGS__, __VA_ARGS__).fatal(); \
+    } \
+    return _kj_result; \
+  }())
+
+#define KJ_EXCEPTION(type, ...) \
+  ::kj::Exception(::kj::Exception::Type::type, __FILE__, __LINE__, \
+      ::kj::_::Debug::makeDescription("" #__VA_ARGS__, __VA_ARGS__))
+
+#else
+
+#define KJ_LOG(severity, ...) \
+  for (bool _kj_shouldLog = ::kj::_::Debug::shouldLog(::kj::LogSeverity::severity); \
+       _kj_shouldLog; _kj_shouldLog = false) \
+    ::kj::_::Debug::log(__FILE__, __LINE__, ::kj::LogSeverity::severity, \
+                        #__VA_ARGS__, ##__VA_ARGS__)
+
+#define KJ_DBG(...) KJ_LOG(DBG, ##__VA_ARGS__)
+
+#define KJ_REQUIRE(cond, ...) \
+  if (auto _kjCondition = ::kj::_::MAGIC_ASSERT << cond) {} else \
+    for (::kj::_::Debug::Fault f(__FILE__, __LINE__, ::kj::Exception::Type::FAILED, \
+        #cond, "_kjCondition," #__VA_ARGS__, _kjCondition, ##__VA_ARGS__);; f.fatal())
+
+#define KJ_FAIL_REQUIRE(...) \
+  for (::kj::_::Debug::Fault f(__FILE__, __LINE__, ::kj::Exception::Type::FAILED, \
+                               nullptr, #__VA_ARGS__, ##__VA_ARGS__);; f.fatal())
+
+#define KJ_SYSCALL(call, ...) \
+  if (auto _kjSyscallResult = ::kj::_::Debug::syscall([&](){return (call);}, false)) {} else \
+    for (::kj::_::Debug::Fault f(__FILE__, __LINE__, \
+             _kjSyscallResult.getErrorNumber(), #call, #__VA_ARGS__, ##__VA_ARGS__);; f.fatal())
+
+#define KJ_NONBLOCKING_SYSCALL(call, ...) \
+  if (auto _kjSyscallResult = ::kj::_::Debug::syscall([&](){return (call);}, true)) {} else \
+    for (::kj::_::Debug::Fault f(__FILE__, __LINE__, \
+             _kjSyscallResult.getErrorNumber(), #call, #__VA_ARGS__, ##__VA_ARGS__);; f.fatal())
+
+#define KJ_FAIL_SYSCALL(code, errorNumber, ...) \
+  for (::kj::_::Debug::Fault f(__FILE__, __LINE__, \
+           errorNumber, code, #__VA_ARGS__, ##__VA_ARGS__);; f.fatal())
+
+#if _WIN32 || __CYGWIN__
+
+#define KJ_WIN32(call, ...) \
+  if (auto _kjWin32Result = ::kj::_::Debug::win32Call(call)) {} else \
+    for (::kj::_::Debug::Fault f(__FILE__, __LINE__, \
+             _kjWin32Result, #call, #__VA_ARGS__, ##__VA_ARGS__);; f.fatal())
+// Invoke a Win32 syscall that returns either BOOL or HANDLE, and throw an exception if it fails.
+
+#define KJ_WINSOCK(call, ...) \
+  if (auto _kjWin32Result = ::kj::_::Debug::winsockCall(call)) {} else \
+    for (::kj::_::Debug::Fault f(__FILE__, __LINE__, \
+             _kjWin32Result, #call, #__VA_ARGS__, ##__VA_ARGS__);; f.fatal())
+// Like KJ_WIN32 but for winsock calls which return `int` with SOCKET_ERROR indicating failure.
+//
+// Unfortunately, it's impossible to distinguish these from BOOL-returning Win32 calls by type,
+// since BOOL is in fact an alias for `int`. :(
+
+#define KJ_FAIL_WIN32(code, errorNumber, ...) \
+  for (::kj::_::Debug::Fault f(__FILE__, __LINE__, \
+           ::kj::_::Debug::Win32Result(errorNumber), code, #__VA_ARGS__, ##__VA_ARGS__);; f.fatal())
+
+#endif
+
+#define KJ_UNIMPLEMENTED(...) \
+  for (::kj::_::Debug::Fault f(__FILE__, __LINE__, ::kj::Exception::Type::UNIMPLEMENTED, \
+                               nullptr, #__VA_ARGS__, ##__VA_ARGS__);; f.fatal())
+
+#define KJ_CONTEXT(...) \
+  auto KJ_UNIQUE_NAME(_kjContextFunc) = [&]() -> ::kj::_::Debug::Context::Value { \
+        return ::kj::_::Debug::Context::Value(__FILE__, __LINE__, \
+            ::kj::_::Debug::makeDescription(#__VA_ARGS__, ##__VA_ARGS__)); \
+      }; \
+  ::kj::_::Debug::ContextImpl<decltype(KJ_UNIQUE_NAME(_kjContextFunc))> \
+      KJ_UNIQUE_NAME(_kjContext)(KJ_UNIQUE_NAME(_kjContextFunc))
+
+#if _MSC_VER && !defined(__clang__)
+
+#define KJ_REQUIRE_NONNULL(value, ...) \
+  (*([&] { \
+    auto _kj_result = ::kj::_::readMaybe(value); \
+    if (KJ_UNLIKELY(!_kj_result)) { \
+      ::kj::_::Debug::Fault(__FILE__, __LINE__, ::kj::Exception::Type::FAILED, \
+                            #value " != nullptr", #__VA_ARGS__, ##__VA_ARGS__).fatal(); \
+    } \
+    return _kj_result; \
+  }()))
+
+#else
+
+#define KJ_REQUIRE_NONNULL(value, ...) \
+  (*({ \
+    auto _kj_result = ::kj::_::readMaybe(value); \
+    if (KJ_UNLIKELY(!_kj_result)) { \
+      ::kj::_::Debug::Fault(__FILE__, __LINE__, ::kj::Exception::Type::FAILED, \
+                            #value " != nullptr", #__VA_ARGS__, ##__VA_ARGS__).fatal(); \
+    } \
+    kj::mv(_kj_result); \
+  }))
+
+#endif
+
+#define KJ_EXCEPTION(type, ...) \
+  ::kj::Exception(::kj::Exception::Type::type, __FILE__, __LINE__, \
+      ::kj::_::Debug::makeDescription(#__VA_ARGS__, ##__VA_ARGS__))
+
+#endif
+
+#define KJ_SYSCALL_HANDLE_ERRORS(call) \
+  if (int _kjSyscallError = ::kj::_::Debug::syscallError([&](){return (call);}, false)) \
+    switch (int error KJ_UNUSED = _kjSyscallError)
+// Like KJ_SYSCALL, but doesn't throw. Instead, the block after the macro is a switch block on the
+// error. Additionally, the int value `error` is defined within the block. So you can do:
+//
+//     KJ_SYSCALL_HANDLE_ERRORS(foo()) {
+//       case ENOENT:
+//         handleNoSuchFile();
+//         break;
+//       case EEXIST:
+//         handleExists();
+//         break;
+//       default:
+//         KJ_FAIL_SYSCALL("foo()", error);
+//     } else {
+//       handleSuccessCase();
+//     }
+
+#if _WIN32 || __CYGWIN__
+
+#define KJ_WIN32_HANDLE_ERRORS(call) \
+  if (uint _kjWin32Error = ::kj::_::Debug::win32Call(call).number) \
+    switch (uint error KJ_UNUSED = _kjWin32Error)
+// Like KJ_WIN32, but doesn't throw. Instead, the block after the macro is a switch block on the
+// error. Additionally, the int value `error` is defined within the block. So you can do:
+//
+//     KJ_SYSCALL_HANDLE_ERRORS(foo()) {
+//       case ERROR_FILE_NOT_FOUND:
+//         handleNoSuchFile();
+//         break;
+//       case ERROR_FILE_EXISTS:
+//         handleExists();
+//         break;
+//       default:
+//         KJ_FAIL_WIN32("foo()", error);
+//     } else {
+//       handleSuccessCase();
+//     }
+
+#endif
+
+#define KJ_ASSERT KJ_REQUIRE
+#define KJ_FAIL_ASSERT KJ_FAIL_REQUIRE
+#define KJ_ASSERT_NONNULL KJ_REQUIRE_NONNULL
+// Use "ASSERT" in place of "REQUIRE" when the problem is local to the immediate surrounding code.
+// That is, if the assert ever fails, it indicates that the immediate surrounding code is broken.
+
+#ifdef KJ_DEBUG
+#define KJ_DLOG KJ_LOG
+#define KJ_DASSERT KJ_ASSERT
+#define KJ_DREQUIRE KJ_REQUIRE
+#define KJ_ASSUME KJ_ASSERT
+#else
+#define KJ_DLOG(...) do {} while (false)
+#define KJ_DASSERT(...) do {} while (false)
+#define KJ_DREQUIRE(...) do {} while (false)
+#if defined(__GNUC__)
+#define KJ_ASSUME(cond, ...) do { if (cond) {} else __builtin_unreachable(); } while (false)
+#elif defined(__clang__)
+#define KJ_ASSUME(cond, ...) __builtin_assume(cond)
+#elif defined(_MSC_VER)
+#define KJ_ASSUME(cond, ...) __assume(cond)
+#else
+#define KJ_ASSUME(...) do {} while (false)
+#endif
+
+#endif
+
+namespace _ {  // private
+
+class Debug {
+public:
+  Debug() = delete;
+
+  typedef LogSeverity Severity;  // backwards-compatibility
+
+#if _WIN32 || __CYGWIN__
+  struct Win32Result {
+    uint number;
+    inline explicit Win32Result(uint number): number(number) {}
+    operator bool() const { return number == 0; }
+  };
+#endif
+
+  static inline bool shouldLog(LogSeverity severity) { return severity >= minSeverity; }
+  // Returns whether messages of the given severity should be logged.
+
+  static inline void setLogLevel(LogSeverity severity) { minSeverity = severity; }
+  // Set the minimum message severity which will be logged.
+  //
+  // TODO(someday):  Expose publicly.
+
+  template <typename... Params>
+  static void log(const char* file, int line, LogSeverity severity, const char* macroArgs,
+                  Params&&... params);
+
+  class Fault {
+  public:
+    template <typename Code, typename... Params>
+    Fault(const char* file, int line, Code code,
+          const char* condition, const char* macroArgs, Params&&... params);
+    Fault(const char* file, int line, Exception::Type type,
+          const char* condition, const char* macroArgs);
+    Fault(const char* file, int line, int osErrorNumber,
+          const char* condition, const char* macroArgs);
+#if _WIN32 || __CYGWIN__
+    Fault(const char* file, int line, Win32Result osErrorNumber,
+          const char* condition, const char* macroArgs);
+#endif
+    ~Fault() noexcept(false);
+
+    KJ_NOINLINE KJ_NORETURN(void fatal());
+    // Throw the exception.
+
+  private:
+    void init(const char* file, int line, Exception::Type type,
+              const char* condition, const char* macroArgs, ArrayPtr<String> argValues);
+    void init(const char* file, int line, int osErrorNumber,
+              const char* condition, const char* macroArgs, ArrayPtr<String> argValues);
+#if _WIN32 || __CYGWIN__
+    void init(const char* file, int line, Win32Result osErrorNumber,
+              const char* condition, const char* macroArgs, ArrayPtr<String> argValues);
+#endif
+
+    Exception* exception;
+  };
+
+  class SyscallResult {
+  public:
+    inline SyscallResult(int errorNumber): errorNumber(errorNumber) {}
+    inline operator void*() { return errorNumber == 0 ? this : nullptr; }
+    inline int getErrorNumber() { return errorNumber; }
+
+  private:
+    int errorNumber;
+  };
+
+  template <typename Call>
+  static SyscallResult syscall(Call&& call, bool nonblocking);
+  template <typename Call>
+  static int syscallError(Call&& call, bool nonblocking);
+
+#if _WIN32 || __CYGWIN__
+  static Win32Result win32Call(int boolean);
+  static Win32Result win32Call(void* handle);
+  static Win32Result winsockCall(int result);
+  static uint getWin32ErrorCode();
+#endif
+
+  class Context: public ExceptionCallback {
+  public:
+    Context();
+    KJ_DISALLOW_COPY_AND_MOVE(Context);
+    virtual ~Context() noexcept(false);
+
+    struct Value {
+      const char* file;
+      int line;
+      String description;
+
+      inline Value(const char* file, int line, String&& description)
+          : file(file), line(line), description(mv(description)) {}
+    };
+
+    virtual Value evaluate() = 0;
+
+    virtual void onRecoverableException(Exception&& exception) override;
+    virtual void onFatalException(Exception&& exception) override;
+    virtual void logMessage(LogSeverity severity, const char* file, int line, int contextDepth,
+                            String&& text) override;
+
+  private:
+    bool logged;
+    Maybe<Value> value;
+
+    Value ensureInitialized();
+  };
+
+  template <typename Func>
+  class ContextImpl: public Context {
+  public:
+    inline ContextImpl(Func& func): func(func) {}
+    KJ_DISALLOW_COPY_AND_MOVE(ContextImpl);
+
+    Value evaluate() override {
+      return func();
+    }
+  private:
+    Func& func;
+  };
+
+  template <typename... Params>
+  static String makeDescription(const char* macroArgs, Params&&... params);
+
+private:
+  static LogSeverity minSeverity;
+
+  static void logInternal(const char* file, int line, LogSeverity severity, const char* macroArgs,
+                          ArrayPtr<String> argValues);
+  static String makeDescriptionInternal(const char* macroArgs, ArrayPtr<String> argValues);
+
+  static int getOsErrorNumber(bool nonblocking);
+  // Get the error code of the last error (e.g. from errno).  Returns -1 on EINTR.
+};
+
+template <typename... Params>
+void Debug::log(const char* file, int line, LogSeverity severity, const char* macroArgs,
+                Params&&... params) {
+  String argValues[sizeof...(Params)] = {str(params)...};
+  logInternal(file, line, severity, macroArgs, arrayPtr(argValues, sizeof...(Params)));
+}
+
+template <>
+inline void Debug::log<>(const char* file, int line, LogSeverity severity, const char* macroArgs) {
+  logInternal(file, line, severity, macroArgs, nullptr);
+}
+
+template <typename Code, typename... Params>
+Debug::Fault::Fault(const char* file, int line, Code code,
+                    const char* condition, const char* macroArgs, Params&&... params)
+    : exception(nullptr) {
+  String argValues[sizeof...(Params)] = {str(params)...};
+  init(file, line, code, condition, macroArgs,
+       arrayPtr(argValues, sizeof...(Params)));
+}
+
+inline Debug::Fault::Fault(const char* file, int line, int osErrorNumber,
+                           const char* condition, const char* macroArgs)
+    : exception(nullptr) {
+  init(file, line, osErrorNumber, condition, macroArgs, nullptr);
+}
+
+inline Debug::Fault::Fault(const char* file, int line, kj::Exception::Type type,
+                           const char* condition, const char* macroArgs)
+    : exception(nullptr) {
+  init(file, line, type, condition, macroArgs, nullptr);
+}
+
+#if _WIN32 || __CYGWIN__
+inline Debug::Fault::Fault(const char* file, int line, Win32Result osErrorNumber,
+                           const char* condition, const char* macroArgs)
+    : exception(nullptr) {
+  init(file, line, osErrorNumber, condition, macroArgs, nullptr);
+}
+
+inline Debug::Win32Result Debug::win32Call(int boolean) {
+  return boolean ? Win32Result(0) : Win32Result(getWin32ErrorCode());
+}
+inline Debug::Win32Result Debug::win32Call(void* handle) {
+  // Assume null and INVALID_HANDLE_VALUE mean failure.
+  return win32Call(handle != nullptr && handle != (void*)-1);
+}
+inline Debug::Win32Result Debug::winsockCall(int result) {
+  // Expect a return value of SOCKET_ERROR means failure.
+  return win32Call(result != -1);
+}
+#endif
+
+template <typename Call>
+Debug::SyscallResult Debug::syscall(Call&& call, bool nonblocking) {
+  while (call() < 0) {
+    int errorNum = getOsErrorNumber(nonblocking);
+    // getOsErrorNumber() returns -1 to indicate EINTR.
+    // Also, if nonblocking is true, then it returns 0 on EAGAIN, which will then be treated as a
+    // non-error.
+    if (errorNum != -1) {
+      return SyscallResult(errorNum);
+    }
+  }
+  return SyscallResult(0);
+}
+
+template <typename Call>
+int Debug::syscallError(Call&& call, bool nonblocking) {
+  while (call() < 0) {
+    int errorNum = getOsErrorNumber(nonblocking);
+    // getOsErrorNumber() returns -1 to indicate EINTR.
+    // Also, if nonblocking is true, then it returns 0 on EAGAIN, which will then be treated as a
+    // non-error.
+    if (errorNum != -1) {
+      return errorNum;
+    }
+  }
+  return 0;
+}
+
+template <typename... Params>
+String Debug::makeDescription(const char* macroArgs, Params&&... params) {
+  String argValues[sizeof...(Params)] = {str(params)...};
+  return makeDescriptionInternal(macroArgs, arrayPtr(argValues, sizeof...(Params)));
+}
+
+template <>
+inline String Debug::makeDescription<>(const char* macroArgs) {
+  return makeDescriptionInternal(macroArgs, nullptr);
+}
+
+// =======================================================================================
+// Magic Asserts!
+//
+// When KJ_ASSERT(foo == bar) fails, `foo` and `bar`'s actual values will be stringified in the
+// error message. How does it work? We use template magic and operator precedence. The assertion
+// actually evaluates something like this:
+//
+//     if (auto _kjCondition = kj::_::MAGIC_ASSERT << foo == bar)
+//
+// `<<` has operator precedence slightly above `==`, so `kj::_::MAGIC_ASSERT << foo` gets evaluated
+// first. This wraps `foo` in a little wrapper that captures the comparison operators and keeps
+// enough information around to be able to stringify the left and right sides of the comparison
+// independently. As always, the stringification only actually occurs if the assert fails.
+//
+// You might ask why we use operator `<<` and not e.g. operator `<=`, since operators of the same
+// precedence are evaluated left-to-right. The answer is that some compilers trigger all sorts of
+// warnings when you seem to be using a comparison as the input to another comparison. The
+// particular warning GCC produces is its general "-Wparentheses" warning which is broadly useful,
+// so we don't want to disable it. `<<` also produces some warnings, but only on Clang and the
+// specific warning is one we're comfortable disabling (see below). This does mean that we have to
+// explicitly overload `operator<<` ourselves to make sure using it in an assert still works.
+//
+// You might also ask, if we're using operator `<<` anyway, why not start it from the right, in
+// which case it would bind after computing any `<<` operators that were actually in the user's
+// code? I tried this, but it resulted in a somewhat broader warning from clang that I felt worse
+// about disabling (a warning about `<<` precedence not applying specifically to overloads) and
+// also created ambiguous overload errors in the KJ units code.
+
+#if __clang__
+// We intentionally overload operator << for the specific purpose of evaluating it before
+// evaluating comparison expressions, so stop Clang from warning about it. Unfortunately this means
+// eliminating a warning that would otherwise be useful for people using iostreams... sorry.
+#pragma GCC diagnostic ignored "-Woverloaded-shift-op-parentheses"
+#endif
+
+template <typename T>
+struct DebugExpression;
+
+template <typename T, typename = decltype(toCharSequence(instance<T&>()))>
+inline auto tryToCharSequence(T* value) { return kj::toCharSequence(*value); }
+inline StringPtr tryToCharSequence(...) { return "(can't stringify)"_kj; }
+// SFINAE to stringify a value if and only if it can be stringified.
+
+template <typename Left, typename Right>
+struct DebugComparison {
+  Left left;
+  Right right;
+  StringPtr op;
+  bool result;
+
+  inline operator bool() const { return KJ_LIKELY(result); }
+
+  template <typename T> inline void operator&(T&& other) = delete;
+  template <typename T> inline void operator^(T&& other) = delete;
+  template <typename T> inline void operator|(T&& other) = delete;
+};
+
+template <typename Left, typename Right>
+String KJ_STRINGIFY(DebugComparison<Left, Right>& cmp) {
+  return _::concat(tryToCharSequence(&cmp.left), cmp.op, tryToCharSequence(&cmp.right));
+}
+
+template <typename T>
+struct DebugExpression {
+  DebugExpression(T&& value): value(kj::fwd<T>(value)) {}
+  T value;
+
+  // Handle comparison operations by constructing a DebugComparison value.
+#define DEFINE_OPERATOR(OP) \
+  template <typename U> \
+  DebugComparison<T, U> operator OP(U&& other) { \
+    bool result = value OP other; \
+    return { kj::fwd<T>(value), kj::fwd<U>(other), " " #OP " "_kj, result }; \
+  }
+  DEFINE_OPERATOR(==);
+  DEFINE_OPERATOR(!=);
+  DEFINE_OPERATOR(<=);
+  DEFINE_OPERATOR(>=);
+  DEFINE_OPERATOR(< );
+  DEFINE_OPERATOR(> );
+#undef DEFINE_OPERATOR
+
+  // Handle binary operators that have equal or lower precedence than comparisons by performing
+  // the operation and wrapping the result.
+#define DEFINE_OPERATOR(OP) \
+  template <typename U> inline auto operator OP(U&& other) { \
+    return DebugExpression<decltype(kj::fwd<T>(value) OP kj::fwd<U>(other))>(\
+        kj::fwd<T>(value) OP kj::fwd<U>(other)); \
+  }
+  DEFINE_OPERATOR(<<);
+  DEFINE_OPERATOR(>>);
+  DEFINE_OPERATOR(&);
+  DEFINE_OPERATOR(^);
+  DEFINE_OPERATOR(|);
+#undef DEFINE_OPERATOR
+
+  inline operator bool() {
+    // No comparison performed, we're just asserting the expression is truthy. This also covers
+    // the case of the logic operators && and || -- we cannot overload those because doing so would
+    // break short-circuiting behavior.
+    return value;
+  }
+};
+
+template <typename T>
+StringPtr KJ_STRINGIFY(const DebugExpression<T>& exp) {
+  // Hack: This will only ever be called in cases where the expression's truthiness was asserted
+  //   directly, and was determined to be falsy.
+  return "false"_kj;
+}
+
+struct DebugExpressionStart {
+  template <typename T>
+  DebugExpression<T> operator<<(T&& value) const {
+    return DebugExpression<T>(kj::fwd<T>(value));
+  }
+};
+static constexpr DebugExpressionStart MAGIC_ASSERT;
+
+}  // namespace _ (private)
+}  // namespace kj
+
+KJ_END_HEADER