comparison osx/include/kj/debug.h @ 49:3ab5a40c4e3b

Add Capnp and KJ builds for OSX

+// 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_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, 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.
+
+#ifndef KJ_DEBUG_H_
+#define KJ_DEBUG_H_
+
+#if defined(__GNUC__) && !KJ_HEADER_WARNINGS
+#pragma GCC system_header
+#endif
+
+#include "string.h"
+#include "exception.h"
+
+#ifdef ERROR
+// This is problematic because windows.h #defines ERROR, which we use in an enum here.
+#error "Make sure to to undefine ERROR (or just #include <kj/windows-sanity.h>) before this file"
+#endif
+
+namespace kj {
+
+#if _MSC_VER
+// 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 appraently 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, ...) \
+  if (!::kj::_::Debug::shouldLog(::kj::LogSeverity::severity)) {} else \
+    ::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 (KJ_LIKELY(cond)) {} else \
+    for (::kj::_::Debug::Fault f(__FILE__, __LINE__, ::kj::Exception::Type::FAILED, \
+                                 #cond, "" #__VA_ARGS__, __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())
+
+#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))
+
+#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, ...) \
+  if (!::kj::_::Debug::shouldLog(::kj::LogSeverity::severity)) {} else \
+    ::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 (KJ_LIKELY(cond)) {} else \
+    for (::kj::_::Debug::Fault f(__FILE__, __LINE__, ::kj::Exception::Type::FAILED, \
+                                 #cond, #__VA_ARGS__, ##__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())
+
+#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))
+
+#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); \
+  }))
+
+#define KJ_EXCEPTION(type, ...) \
+  ::kj::Exception(::kj::Exception::Type::type, __FILE__, __LINE__, \
+      ::kj::_::Debug::makeDescription(#__VA_ARGS__, ##__VA_ARGS__))
+
+#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
+#else
+#define KJ_DLOG(...) do {} while (false)
+#define KJ_DASSERT(...) do {} while (false)
+#define KJ_DREQUIRE(...) do {} while (false)
+#endif
+
+namespace _ {  // private
+
+class Debug {
+public:
+  Debug() = delete;
+
+  typedef LogSeverity Severity;  // backwards-compatibility
+
+  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... Params>
+    Fault(const char* file, int line, Exception::Type type,
+          const char* condition, const char* macroArgs, Params&&... params);
+    template <typename... Params>
+    Fault(const char* file, int line, int osErrorNumber,
+          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);
+    ~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);
+
+    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);
+
+  class Context: public ExceptionCallback {
+  public:
+    Context();
+    KJ_DISALLOW_COPY(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(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... Params>
+Debug::Fault::Fault(const char* file, int line, Exception::Type type,
+                    const char* condition, const char* macroArgs, Params&&... params)
+    : exception(nullptr) {
+  String argValues[sizeof...(Params)] = {str(params)...};
+  init(file, line, type, condition, macroArgs,
+       arrayPtr(argValues, sizeof...(Params)));
+}
+
+template <typename... Params>
+Debug::Fault::Fault(const char* file, int line, int osErrorNumber,
+                    const char* condition, const char* macroArgs, Params&&... params)
+    : exception(nullptr) {
+  String argValues[sizeof...(Params)] = {str(params)...};
+  init(file, line, osErrorNumber, 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);
+}
+
+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... 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);
+}
+
+}  // namespace _ (private)
+}  // namespace kj
+
+#endif  // KJ_DEBUG_H_