Refactored ErrorCode into it's own class

sandbox/linux/seccomp-bpf/die.h

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SANDBOX_LINUX_SECCOMP_BPF_DIE_H__
+#define SANDBOX_LINUX_SECCOMP_BPF_DIE_H__
+
+#include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
+
+
+namespace playground2 {
+
+class Die {
+ public:
+  // We use macros so that the pre-processor can insert appropriate file names
+  // and line numbers, when outputting error messages.
+  #if defined(SECCOMP_BPF_STANDALONE)
+  #define SECCOMP_BPF_FAIL_MACRO(m)                                           \
+    do {                                                                      \
+      Die::LogToStderr(m, __FILE__, __LINE__);                                \
+    } while (false)
+  #else
+  #define SECCOMP_BPF_FAIL_MACRO(m) LOG(FATAL) << (m)
+  #endif
+
+  // This is the main API for using this file. Prints a error message and
+  // exits with a fatal error.
+  #define SANDBOX_DIE(m)                                                      \
+    do {                                                                      \
+      const char *msg = (m);                                                  \
+      if (!Die::CallHandler(msg, __FILE__, __LINE__)) {                       \
+        SECCOMP_BPF_FAIL_MACRO(msg);                                          \
+      }                                                                       \
+      for (;;) {                                                              \
+        /* exit_group() should exit our program. After all, it is          */ \
+        /* defined as a function that doesn't return. But things can       */ \
+        /* theoretically go wrong.  Especially, since we are dealing       */ \
+        /* with system call filters. Continuing execution would be         */ \
+        /* very bad in most cases where die() gets called.  So, if         */ \
+        /* there is no way for us to ask for the program to exit, the      */ \
+        /* next best thing we can do is to loop indefinitely. Maybe,       */ \
+        /* somebody will notice and file a bug...                          */ \
+        syscall(__NR_exit_group, 1);                                          \
+        _exit(1);                                                             \
+      }                                                                       \
+    } while (false)
+
+  // Call back function for custom error handlers. Custom error handlers can be
+  // used when we don't want the default behavior of writing a detailed error
+  // log (possibly including a stack trace). It is normally used, when the
+  // error is handled internally and will never surface to the user.
+  typedef void (*Handler)(const char *msg, const char *file, int line);
+
+  // Use the constructor to push a custom error handler onto the stack. This
+  // simulates dynamic-scoping in C++.
+  Die(Handler handler) { handlers_.push_back(handler); }
+  ~Die() { handlers_.pop_back(); }
+
+  // Calls the top-most error handler function or returns false if there is
+  // no such function.
+  static bool CallHandler(const char *msg, const char *file, int line);
+
+  // Writes a message to stderr. Used as a fall-back choice, if we don't have
+  // any other way to report an error.
+  static void LogToStderr(const char *msg, const char *file, int line);
+
+  static bool HasCustomHandler() { return !handlers_.empty(); }
+
+ private:
+  static std::vector<Handler> handlers_;
+};
+
+}  // namespace
+
+#endif  // SANDBOX_LINUX_SECCOMP_BPF_DIE_H__