196 lines
9.3 KiB
C++
196 lines
9.3 KiB
C++
// Copyright 2017 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// Thread-safe logging routines that do not allocate any memory or
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// acquire any locks, and can therefore be used by low-level memory
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// allocation, synchronization, and signal-handling code.
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#ifndef ABSL_BASE_INTERNAL_RAW_LOGGING_H_
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#define ABSL_BASE_INTERNAL_RAW_LOGGING_H_
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#include <string>
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#include "absl/base/attributes.h"
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#include "absl/base/config.h"
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#include "absl/base/internal/atomic_hook.h"
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#include "absl/base/log_severity.h"
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#include "absl/base/macros.h"
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#include "absl/base/optimization.h"
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#include "absl/base/port.h"
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// This is similar to LOG(severity) << format..., but
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// * it is to be used ONLY by low-level modules that can't use normal LOG()
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// * it is designed to be a low-level logger that does not allocate any
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// memory and does not need any locks, hence:
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// * it logs straight and ONLY to STDERR w/o buffering
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// * it uses an explicit printf-format and arguments list
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// * it will silently chop off really long message strings
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// Usage example:
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// ABSL_RAW_LOG(ERROR, "Failed foo with %i: %s", status, error);
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// This will print an almost standard log line like this to stderr only:
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// E0821 211317 file.cc:123] RAW: Failed foo with 22: bad_file
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#define ABSL_RAW_LOG(severity, ...) \
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do { \
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constexpr const char* absl_raw_logging_internal_basename = \
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::absl::raw_logging_internal::Basename(__FILE__, \
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sizeof(__FILE__) - 1); \
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::absl::raw_logging_internal::RawLog(ABSL_RAW_LOGGING_INTERNAL_##severity, \
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absl_raw_logging_internal_basename, \
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__LINE__, __VA_ARGS__); \
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} while (0)
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// Similar to CHECK(condition) << message, but for low-level modules:
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// we use only ABSL_RAW_LOG that does not allocate memory.
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// We do not want to provide args list here to encourage this usage:
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// if (!cond) ABSL_RAW_LOG(FATAL, "foo ...", hard_to_compute_args);
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// so that the args are not computed when not needed.
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#define ABSL_RAW_CHECK(condition, message) \
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do { \
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if (ABSL_PREDICT_FALSE(!(condition))) { \
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ABSL_RAW_LOG(FATAL, "Check %s failed: %s", #condition, message); \
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} \
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} while (0)
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// ABSL_INTERNAL_LOG and ABSL_INTERNAL_CHECK work like the RAW variants above,
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// except that if the richer log library is linked into the binary, we dispatch
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// to that instead. This is potentially useful for internal logging and
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// assertions, where we are using RAW_LOG neither for its async-signal-safety
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// nor for its non-allocating nature, but rather because raw logging has very
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// few other dependencies.
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//
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// The API is a subset of the above: each macro only takes two arguments. Use
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// StrCat if you need to build a richer message.
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#define ABSL_INTERNAL_LOG(severity, message) \
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do { \
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constexpr const char* absl_raw_logging_internal_filename = __FILE__; \
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::absl::raw_logging_internal::internal_log_function( \
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ABSL_RAW_LOGGING_INTERNAL_##severity, \
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absl_raw_logging_internal_filename, __LINE__, message); \
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if (ABSL_RAW_LOGGING_INTERNAL_##severity == ::absl::LogSeverity::kFatal) \
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ABSL_INTERNAL_UNREACHABLE; \
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} while (0)
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#define ABSL_INTERNAL_CHECK(condition, message) \
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do { \
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if (ABSL_PREDICT_FALSE(!(condition))) { \
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std::string death_message = "Check " #condition " failed: "; \
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death_message += std::string(message); \
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ABSL_INTERNAL_LOG(FATAL, death_message); \
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} \
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} while (0)
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#define ABSL_RAW_LOGGING_INTERNAL_INFO ::absl::LogSeverity::kInfo
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#define ABSL_RAW_LOGGING_INTERNAL_WARNING ::absl::LogSeverity::kWarning
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#define ABSL_RAW_LOGGING_INTERNAL_ERROR ::absl::LogSeverity::kError
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#define ABSL_RAW_LOGGING_INTERNAL_FATAL ::absl::LogSeverity::kFatal
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#define ABSL_RAW_LOGGING_INTERNAL_LEVEL(severity) \
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::absl::NormalizeLogSeverity(severity)
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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namespace raw_logging_internal {
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// Helper function to implement ABSL_RAW_LOG
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// Logs format... at "severity" level, reporting it
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// as called from file:line.
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// This does not allocate memory or acquire locks.
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void RawLog(absl::LogSeverity severity, const char* file, int line,
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const char* format, ...) ABSL_PRINTF_ATTRIBUTE(4, 5);
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// Writes the provided buffer directly to stderr, in a safe, low-level manner.
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//
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// In POSIX this means calling write(), which is async-signal safe and does
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// not malloc. If the platform supports the SYS_write syscall, we invoke that
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// directly to side-step any libc interception.
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void SafeWriteToStderr(const char *s, size_t len);
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// compile-time function to get the "base" filename, that is, the part of
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// a filename after the last "/" or "\" path separator. The search starts at
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// the end of the string; the second parameter is the length of the string.
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constexpr const char* Basename(const char* fname, int offset) {
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return offset == 0 || fname[offset - 1] == '/' || fname[offset - 1] == '\\'
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? fname + offset
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: Basename(fname, offset - 1);
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}
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// For testing only.
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// Returns true if raw logging is fully supported. When it is not
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// fully supported, no messages will be emitted, but a log at FATAL
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// severity will cause an abort.
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//
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// TODO(gfalcon): Come up with a better name for this method.
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bool RawLoggingFullySupported();
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// Function type for a raw_logging customization hook for suppressing messages
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// by severity, and for writing custom prefixes on non-suppressed messages.
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//
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// The installed hook is called for every raw log invocation. The message will
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// be logged to stderr only if the hook returns true. FATAL errors will cause
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// the process to abort, even if writing to stderr is suppressed. The hook is
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// also provided with an output buffer, where it can write a custom log message
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// prefix.
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//
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// The raw_logging system does not allocate memory or grab locks. User-provided
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// hooks must avoid these operations, and must not throw exceptions.
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//
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// 'severity' is the severity level of the message being written.
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// 'file' and 'line' are the file and line number where the ABSL_RAW_LOG macro
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// was located.
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// 'buffer' and 'buf_size' are pointers to the buffer and buffer size. If the
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// hook writes a prefix, it must increment *buffer and decrement *buf_size
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// accordingly.
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using LogPrefixHook = bool (*)(absl::LogSeverity severity, const char* file,
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int line, char** buffer, int* buf_size);
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// Function type for a raw_logging customization hook called to abort a process
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// when a FATAL message is logged. If the provided AbortHook() returns, the
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// logging system will call abort().
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//
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// 'file' and 'line' are the file and line number where the ABSL_RAW_LOG macro
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// was located.
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// The NUL-terminated logged message lives in the buffer between 'buf_start'
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// and 'buf_end'. 'prefix_end' points to the first non-prefix character of the
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// buffer (as written by the LogPrefixHook.)
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using AbortHook = void (*)(const char* file, int line, const char* buf_start,
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const char* prefix_end, const char* buf_end);
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// Internal logging function for ABSL_INTERNAL_LOG to dispatch to.
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//
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// TODO(gfalcon): When string_view no longer depends on base, change this
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// interface to take its message as a string_view instead.
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using InternalLogFunction = void (*)(absl::LogSeverity severity,
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const char* file, int line,
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const std::string& message);
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ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES ABSL_DLL extern base_internal::AtomicHook<
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InternalLogFunction>
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internal_log_function;
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// Registers hooks of the above types. Only a single hook of each type may be
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// registered. It is an error to call these functions multiple times with
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// different input arguments.
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//
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// These functions are safe to call at any point during initialization; they do
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// not block or malloc, and are async-signal safe.
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void RegisterLogPrefixHook(LogPrefixHook func);
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void RegisterAbortHook(AbortHook func);
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void RegisterInternalLogFunction(InternalLogFunction func);
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} // namespace raw_logging_internal
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ABSL_NAMESPACE_END
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} // namespace absl
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#endif // ABSL_BASE_INTERNAL_RAW_LOGGING_H_
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