| // 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/vlog_is_on.h |
| // ----------------------------------------------------------------------------- |
| // |
| // This header defines the `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 (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. |
| // `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_VLOG_IS_ON_H_ |
| #define ABSL_LOG_VLOG_IS_ON_H_ |
| |
| #include "absl/log/absl_vlog_is_on.h" // IWYU pragma: export |
| |
| // IWYU pragma: private, include "absl/log/log.h" |
| |
| // Each 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. |
| // |
| // VLOG_IS_ON is not async signal safe, but it is guaranteed not to allocate |
| // new memory. |
| #define VLOG_IS_ON(verbose_level) ABSL_VLOG_IS_ON(verbose_level) |
| |
| #endif // ABSL_LOG_VLOG_IS_ON_H_ |