116 lines
5.0 KiB
C++
116 lines
5.0 KiB
C++
// Copyright 2022 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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// -----------------------------------------------------------------------------
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// File: log/absl_vlog_is_on.h
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// -----------------------------------------------------------------------------
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//
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// This header defines the `ABSL_VLOG_IS_ON()` macro that controls the
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// variable-verbosity conditional logging.
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//
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// It's used by `VLOG` in log.h, or it can also be used directly like this:
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//
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// if (ABSL_VLOG_IS_ON(2)) {
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// foo_server.RecomputeStatisticsExpensive();
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// LOG(INFO) << foo_server.LastStatisticsAsString();
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// }
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//
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// Each source file has an effective verbosity level that's a non-negative
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// integer computed from the `--vmodule` and `--v` flags.
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// `ABSL_VLOG_IS_ON(n)` is true, and `VLOG(n)` logs, if that effective verbosity
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// level is greater than or equal to `n`.
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//
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// `--vmodule` takes a comma-delimited list of key=value pairs. Each key is a
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// pattern matched against filenames, and the values give the effective severity
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// level applied to matching files. '?' and '*' characters in patterns are
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// interpreted as single-character and zero-or-more-character wildcards.
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// Patterns including a slash character are matched against full pathnames,
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// while those without are matched against basenames only. One suffix (i.e. the
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// last . and everything after it) is stripped from each filename prior to
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// matching, as is the special suffix "-inl".
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//
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// Files are matched against globs in `--vmodule` in order, and the first match
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// determines the verbosity level.
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//
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// Files which do not match any pattern in `--vmodule` use the value of `--v` as
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// their effective verbosity level. The default is 0.
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//
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// SetVLOGLevel helper function is provided to do limited dynamic control over
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// V-logging by appending to `--vmodule`. Because these go at the beginning of
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// the list, they take priority over any globs previously added.
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//
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// Resetting --vmodule will override all previous modifications to `--vmodule`,
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// including via SetVLOGLevel.
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#ifndef ABSL_LOG_ABSL_VLOG_IS_ON_H_
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#define ABSL_LOG_ABSL_VLOG_IS_ON_H_
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#include "absl/base/attributes.h"
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#include "absl/base/config.h"
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#include "absl/log/internal/vlog_config.h" // IWYU pragma: export
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#include "absl/strings/string_view.h"
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// IWYU pragma: private, include "absl/log/log.h"
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// This is expanded at the callsite to allow the compiler to optimize
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// always-false cases out of the build.
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// An ABSL_MAX_VLOG_VERBOSITY of 2 means that VLOG(3) and above should never
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// log.
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#ifdef ABSL_MAX_VLOG_VERBOSITY
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#define ABSL_LOG_INTERNAL_MAX_LOG_VERBOSITY_CHECK(x) \
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((x) <= ABSL_MAX_VLOG_VERBOSITY)&&
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#else
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#define ABSL_LOG_INTERNAL_MAX_LOG_VERBOSITY_CHECK(x)
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#endif
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// Each ABSL_VLOG_IS_ON call site gets its own VLogSite that registers with the
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// global linked list of sites to asynchronously update its verbosity level on
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// changes to --v or --vmodule. The verbosity can also be set by manually
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// calling SetVLOGLevel.
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//
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// ABSL_VLOG_IS_ON is not async signal safe, but it is guaranteed not to
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// allocate new memory.
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#define ABSL_VLOG_IS_ON(verbose_level) \
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(ABSL_LOG_INTERNAL_MAX_LOG_VERBOSITY_CHECK(verbose_level)[]() \
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->::absl::log_internal::VLogSite * \
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{ \
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ABSL_CONST_INIT static ::absl::log_internal::VLogSite site(__FILE__); \
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return &site; \
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}() \
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->IsEnabled(verbose_level))
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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// Sets the global `(ABSL_)VLOG(_IS_ON)` level to `log_level`. This level is
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// applied to any sites whose filename doesn't match any `module_pattern`.
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// Returns the prior value.
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inline int SetGlobalVLogLevel(int log_level) {
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return absl::log_internal::UpdateGlobalVLogLevel(log_level);
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}
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// Sets `(ABSL_)VLOG(_IS_ON)` level for `module_pattern` to `log_level`.
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// This lets us dynamically control what is normally set by the --vmodule flag.
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// Returns the level that previously applied to module_pattern.
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// Calling this with `log_level` of kUseFlag will have all sites for that
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// pattern use the value of --v.
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inline int SetVLogLevel(absl::string_view module_pattern, int log_level) {
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return absl::log_internal::PrependVModule(module_pattern, log_level);
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}
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ABSL_NAMESPACE_END
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} // namespace absl
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#endif // ABSL_LOG_ABSL_VLOG_IS_ON_H_
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