1// Copyright 2017 The Abseil Authors.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7// https://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14//
15// Thread-safe logging routines that do not allocate any memory or
16// acquire any locks, and can therefore be used by low-level memory
17// allocation, synchronization, and signal-handling code.
18
19#ifndef ABSL_BASE_INTERNAL_RAW_LOGGING_H_
20#define ABSL_BASE_INTERNAL_RAW_LOGGING_H_
21
22#include <string>
23
24#include "absl/base/attributes.h"
25#include "absl/base/config.h"
26#include "absl/base/internal/atomic_hook.h"
27#include "absl/base/log_severity.h"
28#include "absl/base/macros.h"
29#include "absl/base/optimization.h"
30#include "absl/base/port.h"
31
32// This is similar to LOG(severity) << format..., but
33// * it is to be used ONLY by low-level modules that can't use normal LOG()
34// * it is designed to be a low-level logger that does not allocate any
35// memory and does not need any locks, hence:
36// * it logs straight and ONLY to STDERR w/o buffering
37// * it uses an explicit printf-format and arguments list
38// * it will silently chop off really long message strings
39// Usage example:
40// ABSL_RAW_LOG(ERROR, "Failed foo with %i: %s", status, error);
41// This will print an almost standard log line like this to stderr only:
42// E0821 211317 file.cc:123] RAW: Failed foo with 22: bad_file
43
44#define ABSL_RAW_LOG(severity, ...) \
45 do { \
46 constexpr const char* absl_raw_logging_internal_basename = \
47 ::absl::raw_logging_internal::Basename(__FILE__, \
48 sizeof(__FILE__) - 1); \
49 ::absl::raw_logging_internal::RawLog(ABSL_RAW_LOGGING_INTERNAL_##severity, \
50 absl_raw_logging_internal_basename, \
51 __LINE__, __VA_ARGS__); \
52 } while (0)
53
54// Similar to CHECK(condition) << message, but for low-level modules:
55// we use only ABSL_RAW_LOG that does not allocate memory.
56// We do not want to provide args list here to encourage this usage:
57// if (!cond) ABSL_RAW_LOG(FATAL, "foo ...", hard_to_compute_args);
58// so that the args are not computed when not needed.
59#define ABSL_RAW_CHECK(condition, message) \
60 do { \
61 if (ABSL_PREDICT_FALSE(!(condition))) { \
62 ABSL_RAW_LOG(FATAL, "Check %s failed: %s", #condition, message); \
63 } \
64 } while (0)
65
66// ABSL_INTERNAL_LOG and ABSL_INTERNAL_CHECK work like the RAW variants above,
67// except that if the richer log library is linked into the binary, we dispatch
68// to that instead. This is potentially useful for internal logging and
69// assertions, where we are using RAW_LOG neither for its async-signal-safety
70// nor for its non-allocating nature, but rather because raw logging has very
71// few other dependencies.
72//
73// The API is a subset of the above: each macro only takes two arguments. Use
74// StrCat if you need to build a richer message.
75#define ABSL_INTERNAL_LOG(severity, message) \
76 do { \
77 constexpr const char* absl_raw_logging_internal_filename = __FILE__; \
78 ::absl::raw_logging_internal::internal_log_function( \
79 ABSL_RAW_LOGGING_INTERNAL_##severity, \
80 absl_raw_logging_internal_filename, __LINE__, message); \
81 if (ABSL_RAW_LOGGING_INTERNAL_##severity == ::absl::LogSeverity::kFatal) \
82 ABSL_INTERNAL_UNREACHABLE; \
83 } while (0)
84
85#define ABSL_INTERNAL_CHECK(condition, message) \
86 do { \
87 if (ABSL_PREDICT_FALSE(!(condition))) { \
88 std::string death_message = "Check " #condition " failed: "; \
89 death_message += std::string(message); \
90 ABSL_INTERNAL_LOG(FATAL, death_message); \
91 } \
92 } while (0)
93
94#define ABSL_RAW_LOGGING_INTERNAL_INFO ::absl::LogSeverity::kInfo
95#define ABSL_RAW_LOGGING_INTERNAL_WARNING ::absl::LogSeverity::kWarning
96#define ABSL_RAW_LOGGING_INTERNAL_ERROR ::absl::LogSeverity::kError
97#define ABSL_RAW_LOGGING_INTERNAL_FATAL ::absl::LogSeverity::kFatal
98#define ABSL_RAW_LOGGING_INTERNAL_LEVEL(severity) \
99 ::absl::NormalizeLogSeverity(severity)
100
101namespace absl {
102ABSL_NAMESPACE_BEGIN
103namespace raw_logging_internal {
104
105// Helper function to implement ABSL_RAW_LOG
106// Logs format... at "severity" level, reporting it
107// as called from file:line.
108// This does not allocate memory or acquire locks.
109void RawLog(absl::LogSeverity severity, const char* file, int line,
110 const char* format, ...) ABSL_PRINTF_ATTRIBUTE(4, 5);
111
112// Writes the provided buffer directly to stderr, in a signal-safe, low-level
113// manner.
114void AsyncSignalSafeWriteToStderr(const char* s, size_t len);
115
116// compile-time function to get the "base" filename, that is, the part of
117// a filename after the last "/" or "\" path separator. The search starts at
118// the end of the string; the second parameter is the length of the string.
119constexpr const char* Basename(const char* fname, int offset) {
120 return offset == 0 || fname[offset - 1] == '/' || fname[offset - 1] == '\\'
121 ? fname + offset
122 : Basename(fname, offset: offset - 1);
123}
124
125// For testing only.
126// Returns true if raw logging is fully supported. When it is not
127// fully supported, no messages will be emitted, but a log at FATAL
128// severity will cause an abort.
129//
130// TODO(gfalcon): Come up with a better name for this method.
131bool RawLoggingFullySupported();
132
133// Function type for a raw_logging customization hook for suppressing messages
134// by severity, and for writing custom prefixes on non-suppressed messages.
135//
136// The installed hook is called for every raw log invocation. The message will
137// be logged to stderr only if the hook returns true. FATAL errors will cause
138// the process to abort, even if writing to stderr is suppressed. The hook is
139// also provided with an output buffer, where it can write a custom log message
140// prefix.
141//
142// The raw_logging system does not allocate memory or grab locks. User-provided
143// hooks must avoid these operations, and must not throw exceptions.
144//
145// 'severity' is the severity level of the message being written.
146// 'file' and 'line' are the file and line number where the ABSL_RAW_LOG macro
147// was located.
148// 'buf' and 'buf_size' are pointers to the buffer and buffer size. If the
149// hook writes a prefix, it must increment *buf and decrement *buf_size
150// accordingly.
151using LogFilterAndPrefixHook = bool (*)(absl::LogSeverity severity,
152 const char* file, int line, char** buf,
153 int* buf_size);
154
155// Function type for a raw_logging customization hook called to abort a process
156// when a FATAL message is logged. If the provided AbortHook() returns, the
157// logging system will call abort().
158//
159// 'file' and 'line' are the file and line number where the ABSL_RAW_LOG macro
160// was located.
161// The NUL-terminated logged message lives in the buffer between 'buf_start'
162// and 'buf_end'. 'prefix_end' points to the first non-prefix character of the
163// buffer (as written by the LogFilterAndPrefixHook.)
164//
165// The lifetime of the filename and message buffers will not end while the
166// process remains alive.
167using AbortHook = void (*)(const char* file, int line, const char* buf_start,
168 const char* prefix_end, const char* buf_end);
169
170// Internal logging function for ABSL_INTERNAL_LOG to dispatch to.
171//
172// TODO(gfalcon): When string_view no longer depends on base, change this
173// interface to take its message as a string_view instead.
174using InternalLogFunction = void (*)(absl::LogSeverity severity,
175 const char* file, int line,
176 const std::string& message);
177
178ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES ABSL_DLL extern base_internal::AtomicHook<
179 InternalLogFunction>
180 internal_log_function;
181
182// Registers hooks of the above types. Only a single hook of each type may be
183// registered. It is an error to call these functions multiple times with
184// different input arguments.
185//
186// These functions are safe to call at any point during initialization; they do
187// not block or malloc, and are async-signal safe.
188void RegisterLogFilterAndPrefixHook(LogFilterAndPrefixHook func);
189void RegisterAbortHook(AbortHook func);
190void RegisterInternalLogFunction(InternalLogFunction func);
191
192} // namespace raw_logging_internal
193ABSL_NAMESPACE_END
194} // namespace absl
195
196#endif // ABSL_BASE_INTERNAL_RAW_LOGGING_H_
197

source code of include/absl/base/internal/raw_logging.h