| // Copyright (c) 2006-2009 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| // Defines the VLOG_IS_ON macro that controls the variable-verbosity |
| // conditional logging. |
| // |
| // It's used by VLOG and VLOG_IF in logging.h |
| // and by RAW_VLOG in raw_logging.h to trigger the logging. |
| // |
| // It can also be used directly e.g. like this: |
| // if (VLOG_IS_ON(2)) { |
| // // do some logging preparation and logging |
| // // that can't be accomplished e.g. via just VLOG(2) << ...; |
| // } |
| // |
| // The truth value that VLOG_IS_ON(level) returns is determined by |
| // the three verbosity level flags: |
| // --v=<n> Gives the default maximal active V-logging level; |
| // 0 is the default. |
| // Normally positive values are used for V-logging levels. |
| // --vmodule=<str> Gives the per-module maximal V-logging levels to override |
| // the value given by --v. |
| // E.g. "my_module=2,foo*=3" would change the logging level |
| // for all code in source files "my_module.*" and "foo*.*" |
| // ("-inl" suffixes are also disregarded for this matching). |
| // --silent_init When true has the effect of increasing |
| // the argument of VLOG_IS_ON by 1, |
| // thus suppressing one more level of verbose logging. |
| // |
| // SetVLOGLevel helper function is provided to do limited dynamic control over |
| // V-logging by overriding the per-module settings given via --vmodule flag. |
| // |
| // CAVEAT: --vmodule functionality is not available in non gcc compilers. |
| // |
| |
| #ifndef BASE_VLOG_IS_ON_H_ |
| #define BASE_VLOG_IS_ON_H_ |
| |
| #include "base/atomicops.h" |
| #include "base/basictypes.h" |
| #include "base/port.h" |
| #include "base/commandlineflags.h" |
| #include "base/log_severity.h" |
| |
| DECLARE_int32(v); // in vlog_is_on.cc |
| DECLARE_bool(silent_init); // in google.cc |
| |
| #if defined(__GNUC__) |
| // We pack an int16 verbosity level and an int16 epoch into an |
| // Atomic32 at every VLOG_IS_ON() call site. The level determines |
| // whether the site should log, and the epoch determines whether the |
| // site is stale and should be reinitialized. A verbosity level of |
| // kUseFlag (-1) indicates that the value of FLAGS_v should be used as |
| // the verbosity level. When the site is (re)initialized, a verbosity |
| // level for the current source file is retrieved from an internal |
| // list. This list is mutated through calls to SetVLOGLevel() and |
| // mutations to the --vmodule flag. New log sites are initialized |
| // with a stale epoch and a verbosity level of kUseFlag. |
| // |
| // TODO(llansing): Investigate using GCC's __builtin_constant_p() to |
| // generate less code at call sites where verbositylevel is known to |
| // be a compile-time constant. |
| #define VLOG_IS_ON(verboselevel) \ |
| ({ static Atomic32 site__ = ::base::internal::kDefaultSite; \ |
| ::base::internal::VLogEnabled(&site__, (verboselevel), __FILE__); }) |
| #else |
| // GNU extensions not available, so we do not support --vmodule. |
| // Dynamic value of FLAGS_v always controls the logging level. |
| // |
| // TODO(llansing): Investigate supporting --vmodule on other platforms. |
| #define VLOG_IS_ON(verboselevel) \ |
| (FLAGS_v >= (verboselevel) + FLAGS_silent_init) |
| #endif |
| |
| // Set VLOG(_IS_ON) level for module_pattern to log_level. |
| // This lets us dynamically control what is normally set by the --vmodule flag. |
| // Returns the level that previously applied to module_pattern. |
| // NOTE: To change the log level for VLOG(_IS_ON) sites |
| // that have already executed after/during InitGoogle, |
| // one needs to supply the exact --vmodule pattern that applied to them. |
| // (If no --vmodule pattern applied to them |
| // the value of FLAGS_v will continue to control them.) |
| int SetVLOGLevel(const char* module_pattern, int log_level); |
| |
| // Private implementation details. No user-serviceable parts inside. |
| namespace base { |
| namespace internal { |
| |
| // Each log site determines whether its log level is up to date by |
| // comparing its epoch to this global epoch. Whenever the program's |
| // vmodule configuration changes (ex: SetVLOGLevel is called), the |
| // global epoch is advanced, invalidating all site epochs. |
| extern Atomic32 vlog_epoch; |
| |
| // A log level of kUseFlag means "read the logging level from FLAGS_v." |
| const int kUseFlag = -1; |
| |
| // Log sites use FLAGS_v by default, and have an initial epoch of 0. |
| const Atomic32 kDefaultSite = kUseFlag << 16; |
| |
| // The global epoch is the least significant half of an Atomic32, and |
| // may only be accessed through atomic operations. |
| inline Atomic32 GlobalEpoch() { |
| return Acquire_Load(&vlog_epoch) & 0x0000FFFF; |
| } |
| |
| // The least significant half of a site is the epoch. |
| inline int SiteEpoch(Atomic32 site) { return site & 0x0000FFFF; } |
| |
| // The most significant half of a site is the logging level. |
| inline int SiteLevel(Atomic32 site) { return site >> 16; } |
| |
| // Construct a logging site from a logging level and epoch. |
| inline Atomic32 Site(int level, int epoch) { |
| return ((level & 0x0000FFFF) << 16) | (epoch & 0x0000FFFF); |
| } |
| |
| // Attempt to initialize or reinitialize a VLOG site. Returns the |
| // level of the log site, regardless of whether the attempt succeeds |
| // or fails. |
| // site: The address of the log site's state. |
| // fname: The filename of the current source file. |
| int InitVLOG(Atomic32* site, const char* fname); |
| |
| // Determine whether verbose logging should occur at a given log site. |
| // |
| // TODO(llansing): Find a way to eliminate FLAGS_silent_init from this |
| // function while preserving the silent initialization behavior. The |
| // common-case code path shouldn't pay for silent initialization. |
| inline bool VLogEnabled(Atomic32* site, int32 level, const char* const file) { |
| const Atomic32 site_copy = Acquire_Load(site); |
| const int32 site_level = |
| PREDICT_TRUE(SiteEpoch(site_copy) == GlobalEpoch()) ? |
| SiteLevel(site_copy) : InitVLOG(site, file); |
| return (site_level == kUseFlag ? FLAGS_v : site_level) >= |
| (level + FLAGS_silent_init); |
| } |
| |
| } // namespace internal |
| } // namespace base |
| |
| #endif // BASE_VLOG_IS_ON_H_ |