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authorGravatar misterg <misterg@google.com>2017-09-19 16:54:40 -0400
committerGravatar misterg <misterg@google.com>2017-09-19 16:54:40 -0400
commitc2e754829628d1e9b7a16b3389cfdace76950fdf (patch)
tree5a7f056f44e27c30e10025113b644f0b3b5801fc /absl/base/internal/raw_logging.h
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+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Thread-safe logging routines that do not allocate any memory or
+// acquire any locks, and can therefore be used by low-level memory
+// allocation, synchronization, and signal-handling code.
+
+#ifndef ABSL_BASE_INTERNAL_RAW_LOGGING_H_
+#define ABSL_BASE_INTERNAL_RAW_LOGGING_H_
+
+#include "absl/base/internal/log_severity.h"
+#include "absl/base/macros.h"
+#include "absl/base/port.h"
+
+// This is similar to LOG(severity) << format..., but
+// * it is to be used ONLY by low-level modules that can't use normal LOG()
+// * it is designed to be a low-level logger that does not allocate any
+// memory and does not need any locks, hence:
+// * it logs straight and ONLY to STDERR w/o buffering
+// * it uses an explicit printf-format and arguments list
+// * it will silently chop off really long message strings
+// Usage example:
+// ABSL_RAW_LOG(ERROR, "Failed foo with %i: %s", status, error);
+// This will print an almost standard log line like this to stderr only:
+// E0821 211317 file.cc:123] RAW: Failed foo with 22: bad_file
+#define ABSL_RAW_LOG(severity, ...) \
+ do { \
+ constexpr const char* absl_raw_logging_internal_basename = \
+ ::absl::raw_logging_internal::Basename(__FILE__, \
+ sizeof(__FILE__) - 1); \
+ ::absl::raw_logging_internal::RawLog(ABSL_RAW_LOGGING_INTERNAL_##severity, \
+ absl_raw_logging_internal_basename, \
+ __LINE__, __VA_ARGS__); \
+ } while (0)
+
+// Similar to CHECK(condition) << message, but for low-level modules:
+// we use only ABSL_RAW_LOG that does not allocate memory.
+// We do not want to provide args list here to encourage this usage:
+// if (!cond) ABSL_RAW_LOG(FATAL, "foo ...", hard_to_compute_args);
+// so that the args are not computed when not needed.
+#define ABSL_RAW_CHECK(condition, message) \
+ do { \
+ if (ABSL_PREDICT_FALSE(!(condition))) { \
+ ABSL_RAW_LOG(FATAL, "Check %s failed: %s", #condition, message); \
+ } \
+ } while (0)
+
+#define ABSL_RAW_LOGGING_INTERNAL_INFO ::absl::LogSeverity::kInfo
+#define ABSL_RAW_LOGGING_INTERNAL_WARNING ::absl::LogSeverity::kWarning
+#define ABSL_RAW_LOGGING_INTERNAL_ERROR ::absl::LogSeverity::kError
+#define ABSL_RAW_LOGGING_INTERNAL_FATAL ::absl::LogSeverity::kFatal
+#define ABSL_RAW_LOGGING_INTERNAL_LEVEL(severity) \
+ ::absl::NormalizeLogSeverity(severity)
+
+namespace absl {
+namespace raw_logging_internal {
+
+// Helper function to implement ABSL_RAW_LOG
+// Logs format... at "severity" level, reporting it
+// as called from file:line.
+// This does not allocate memory or acquire locks.
+void RawLog(absl::LogSeverity severity, const char* file, int line,
+ const char* format, ...) ABSL_PRINTF_ATTRIBUTE(4, 5);
+
+// compile-time function to get the "base" filename, that is, the part of
+// a filename after the last "/" or "\" path separator. The search starts at
+// the end of the std::string; the second parameter is the length of the std::string.
+constexpr const char* Basename(const char* fname, int offset) {
+ return offset == 0 || fname[offset - 1] == '/' || fname[offset - 1] == '\\'
+ ? fname + offset
+ : Basename(fname, offset - 1);
+}
+
+// For testing only.
+// Returns true if raw logging is fully supported. When it is not
+// fully supported, no messages will be emitted, but a log at FATAL
+// severity will cause an abort.
+//
+// TODO(gfalcon): Come up with a better name for this method.
+bool RawLoggingFullySupported();
+
+// Function type for a raw_logging customization hook for suppressing messages
+// by severity, and for writing custom prefixes on non-suppressed messages.
+//
+// The installed hook is called for every raw log invocation. The message will
+// be logged to stderr only if the hook returns true. FATAL errors will cause
+// the process to abort, even if writing to stderr is suppressed. The hook is
+// also provided with an output buffer, where it can write a custom log message
+// prefix.
+//
+// The raw_logging system does not allocate memory or grab locks. User-provided
+// hooks must avoid these operations, and must not throw exceptions.
+//
+// 'severity' is the severity level of the message being written.
+// 'file' and 'line' are the file and line number where the ABSL_RAW_LOG macro
+// was located.
+// 'buffer' and 'buf_size' are pointers to the buffer and buffer size. If the
+// hook writes a prefix, it must increment *buffer and decrement *buf_size
+// accordingly.
+using LogPrefixHook = bool (*)(absl::LogSeverity severity, const char* file,
+ int line, char** buffer, int* buf_size);
+
+// Function type for a raw_logging customization hook called to abort a process
+// when a FATAL message is logged. If the provided AbortHook() returns, the
+// logging system will call abort().
+//
+// 'file' and 'line' are the file and line number where the ABSL_RAW_LOG macro
+// was located.
+// The null-terminated logged message lives in the buffer between 'buf_start'
+// and 'buf_end'. 'prefix_end' points to the first non-prefix character of the
+// buffer (as written by the LogPrefixHook.)
+using AbortHook = void (*)(const char* file, int line, const char* buf_start,
+ const char* prefix_end, const char* buf_end);
+
+} // namespace raw_logging_internal
+} // namespace absl
+
+#endif // ABSL_BASE_INTERNAL_RAW_LOGGING_H_