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Diffstat (limited to 'absl/log/absl_vlog_is_on.h')
| -rw-r--r-- | absl/log/absl_vlog_is_on.h | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/absl/log/absl_vlog_is_on.h b/absl/log/absl_vlog_is_on.h new file mode 100644 index 00000000..29096b48 --- /dev/null +++ b/absl/log/absl_vlog_is_on.h @@ -0,0 +1,93 @@ +// 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. +// +// ----------------------------------------------------------------------------- +// File: log/absl_vlog_is_on.h +// ----------------------------------------------------------------------------- +// +// This header defines the `ABSL_VLOG_IS_ON()` macro that controls the +// variable-verbosity conditional logging. +// +// It's used by `VLOG` in log.h, or it can also be used directly like this: +// +// if (ABSL_VLOG_IS_ON(2)) { +// foo_server.RecomputeStatisticsExpensive(); +// LOG(INFO) << foo_server.LastStatisticsAsString(); +// } +// +// Each source file has an effective verbosity level that's a non-negative +// integer computed from the `--vmodule` and `--v` flags. +// `ABSL_VLOG_IS_ON(n)` is true, and `VLOG(n)` logs, if that effective verbosity +// level is greater than or equal to `n`. +// +// `--vmodule` takes a comma-delimited list of key=value pairs. Each key is a +// pattern matched against filenames, and the values give the effective severity +// level applied to matching files. '?' and '*' characters in patterns are +// interpreted as single-character and zero-or-more-character wildcards. +// Patterns including a slash character are matched against full pathnames, +// while those without are matched against basenames only. One suffix (i.e. the +// last . and everything after it) is stripped from each filename prior to +// matching, as is the special suffix "-inl". +// +// Files are matched against globs in `--vmodule` in order, and the first match +// determines the verbosity level. +// +// Files which do not match any pattern in `--vmodule` use the value of `--v` as +// their effective verbosity level. The default is 0. +// +// SetVLOGLevel helper function is provided to do limited dynamic control over +// V-logging by appending to `--vmodule`. Because these go at the beginning of +// the list, they take priority over any globs previously added. +// +// Resetting --vmodule will override all previous modifications to `--vmodule`, +// including via SetVLOGLevel. + +#ifndef ABSL_LOG_ABSL_VLOG_IS_ON_H_ +#define ABSL_LOG_ABSL_VLOG_IS_ON_H_ + +#include "absl/base/attributes.h" +#include "absl/base/config.h" +#include "absl/log/internal/vlog_config.h" // IWYU pragma: export +#include "absl/strings/string_view.h" + +// IWYU pragma: private, include "absl/log/log.h" + +// This is expanded at the callsite to allow the compiler to optimize +// always-false cases out of the build. +// An ABSL_MAX_VLOG_VERBOSITY of 2 means that VLOG(3) and above should never +// log. +#ifdef ABSL_MAX_VLOG_VERBOSITY +#define ABSL_LOG_INTERNAL_MAX_LOG_VERBOSITY_CHECK(x) \ + ((x) <= ABSL_MAX_VLOG_VERBOSITY)&& +#else +#define ABSL_LOG_INTERNAL_MAX_LOG_VERBOSITY_CHECK(x) +#endif + +// Each ABSL_VLOG_IS_ON call site gets its own VLogSite that registers with the +// global linked list of sites to asynchronously update its verbosity level on +// changes to --v or --vmodule. The verbosity can also be set by manually +// calling SetVLOGLevel. +// +// ABSL_VLOG_IS_ON is not async signal safe, but it is guaranteed not to +// allocate new memory. +#define ABSL_VLOG_IS_ON(verbose_level) \ + (ABSL_LOG_INTERNAL_MAX_LOG_VERBOSITY_CHECK(verbose_level)[]() \ + ->::absl::log_internal::VLogSite * \ + { \ + ABSL_CONST_INIT static ::absl::log_internal::VLogSite site(__FILE__); \ + return &site; \ + }() \ + ->IsEnabled(verbose_level)) + +#endif // ABSL_LOG_ABSL_VLOG_IS_ON_H_ |