vlog_is_on.h (3237B)
1 // Copyright 2022 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 // ----------------------------------------------------------------------------- 16 // File: log/vlog_is_on.h 17 // ----------------------------------------------------------------------------- 18 // 19 // This header defines the `VLOG_IS_ON()` macro that controls the 20 // variable-verbosity conditional logging. 21 // 22 // It's used by `VLOG` in log.h, or it can also be used directly like this: 23 // 24 // if (VLOG_IS_ON(2)) { 25 // foo_server.RecomputeStatisticsExpensive(); 26 // LOG(INFO) << foo_server.LastStatisticsAsString(); 27 // } 28 // 29 // Each source file has an effective verbosity level that's a non-negative 30 // integer computed from the `--vmodule` and `--v` flags. 31 // `VLOG_IS_ON(n)` is true, and `VLOG(n)` logs, if that effective verbosity 32 // level is greater than or equal to `n`. 33 // 34 // `--vmodule` takes a comma-delimited list of key=value pairs. Each key is a 35 // pattern matched against filenames, and the values give the effective severity 36 // level applied to matching files. '?' and '*' characters in patterns are 37 // interpreted as single-character and zero-or-more-character wildcards. 38 // Patterns including a slash character are matched against full pathnames, 39 // while those without are matched against basenames only. One suffix (i.e. the 40 // last . and everything after it) is stripped from each filename prior to 41 // matching, as is the special suffix "-inl". 42 // 43 // Example: --vmodule=module_a=1,module_b=2 44 // 45 // Files are matched against globs in `--vmodule` in order, and the first match 46 // determines the verbosity level. 47 // 48 // Files which do not match any pattern in `--vmodule` use the value of `--v` as 49 // their effective verbosity level. The default is 0. 50 // 51 // SetVLogLevel helper function is provided to do limited dynamic control over 52 // V-logging by appending to `--vmodule`. Because these go at the beginning of 53 // the list, they take priority over any globs previously added. 54 // 55 // Resetting --vmodule will override all previous modifications to `--vmodule`, 56 // including via SetVLogLevel. 57 58 #ifndef ABSL_LOG_VLOG_IS_ON_H_ 59 #define ABSL_LOG_VLOG_IS_ON_H_ 60 61 #include "absl/log/absl_vlog_is_on.h" // IWYU pragma: export 62 63 // IWYU pragma: private, include "absl/log/log.h" 64 65 // Each VLOG_IS_ON call site gets its own VLogSite that registers with the 66 // global linked list of sites to asynchronously update its verbosity level on 67 // changes to --v or --vmodule. The verbosity can also be set by manually 68 // calling SetVLogLevel. 69 // 70 // VLOG_IS_ON is not async signal safe, but it is guaranteed not to allocate 71 // new memory. 72 #define VLOG_IS_ON(verbose_level) ABSL_VLOG_IS_ON(verbose_level) 73 74 #endif // ABSL_LOG_VLOG_IS_ON_H_