chromium/third_party/abseil-cpp/absl/log/internal/vlog_config.h

// Copyright 2022 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
//
//     https://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.
//
// -----------------------------------------------------------------------------
// vlog_config.h
// -----------------------------------------------------------------------------
//
// This header file defines `VLogSite`, a public primitive that represents
// a callsite for the `VLOG` family of macros and related libraries.
// It also declares and defines multiple internal utilities used to implement
// `VLOG`, such as `VLogSiteManager`.

#ifndef ABSL_LOG_INTERNAL_VLOG_CONFIG_H_
#define ABSL_LOG_INTERNAL_VLOG_CONFIG_H_

// IWYU pragma: private, include "absl/log/log.h"

#include <atomic>
#include <cstdint>
#include <functional>
#include <limits>
#include <type_traits>

#include "absl/base/attributes.h"
#include "absl/base/config.h"
#include "absl/base/optimization.h"
#include "absl/base/thread_annotations.h"
#include "absl/strings/string_view.h"

namespace absl {
ABSL_NAMESPACE_BEGIN
namespace log_internal {

class SyntheticBinary;
class VLogSite;

int RegisterAndInitialize(VLogSite* v);
void UpdateVLogSites();
constexpr int kUseFlag = (std::numeric_limits<int16_t>::min)();

// Represents a unique callsite for a `VLOG()` or `VLOG_IS_ON()` call.
//
// Libraries that provide `VLOG`-like functionality should use this to
// efficiently handle --vmodule.
//
// VLogSite objects must not be destroyed until the program exits. Doing so will
// probably yield nasty segfaults in VLogSiteManager::UpdateLogSites(). The
// recommendation is to make all such objects function-local statics.
class VLogSite final { … };
static_assert(std::is_trivially_destructible<VLogSite>::value,
              "VLogSite must be trivially destructible");

// Returns the current verbose log level of `file`.
// Does not allocate memory.
int VLogLevel(absl::string_view file);

// Registers a site `v` to get updated as `vmodule` and `v` change.  Also
// initializes the site based on their current values, and returns that result.
// Does not allocate memory.
int RegisterAndInitialize(VLogSite* v);

// Allocates memory.
void UpdateVLogSites();

// Completely overwrites the saved value of `vmodule`.
// Allocates memory.
void UpdateVModule(absl::string_view vmodule);

// Updates the global verbosity level to `v` and returns the prior value.
// Allocates memory.
int UpdateGlobalVLogLevel(int v);

// Atomically prepends `module_pattern=log_level` to the start of vmodule.
// Returns the prior value for `module_pattern` if there was an exact match and
// `global_v` otherwise.
// Allocates memory.
int PrependVModule(absl::string_view module_pattern, int log_level);

// Registers `on_update` to be called whenever `v` or `vmodule` change.
// Allocates memory.
void OnVLogVerbosityUpdate(std::function<void()> cb);

// Does not allocate memory.
VLogSite* SetVModuleListHeadForTestOnly(VLogSite* v);

}  // namespace log_internal
ABSL_NAMESPACE_END
}  // namespace absl

#endif  // ABSL_LOG_INTERNAL_VLOG_CONFIG_H_