-/**
-@page outcomes_logs Simulation Logging
-@brief Log4J-like logging system.
-
-Using @c printf or @c println to display information is possible, but
-quickly unpractical, as the logs of all processes get intermixed in
-your program's output. As an answer, the SimGrid logging module allow
-you to sort and filter the logs by emitter, by module and by gravity
-level.
-
-The SimGrid logging module is highly <b>configurable</b>: as in Log4J,
-the user can choose <i>at runtime</i> what messages to show and what
-to hide, as well as how messages get displayed. It is also <b>easy to
-use</b>, both to the programmer (using preprocessor macros black
-magic) and to the user (with command line options). And finally, its
-<b>performance</b> is highly optimized.
-
-@tableofcontents
-
-@section log_overview Main Concepts
-
-There is three main concepts in SimGrid's logging mechanism:
-** **category**, **priority** and **appender**. These three concepts work
-together to enable developers to log messages according to message
-type and priority, and to control at runtime how these messages are
-formatted and where they are reported.
-
-@subsection log_cat Logging categories
-
-In SimGrid, the logs are sorted by topics (called categories) so that
-the user can chose which topics to display and hide at runtime. These
-categories are organized as a hierarchy, following the architecture of
-modules in the simulator.
-
-The full list of all categories that exist in the SimGrid base library
-@ref XBT_log_cats "is available in the documentation".
-You can also provide ```--help-logs``` on the command line of any
-SimGrid simulator to see the list of all existing categories that it
-contains.
-
-@subsection log_pri Logging priorities
-
-The user can also specify the desired level of details for each category. This is
-controlled by the <i>priority</i> concept (which should maybe be renamed to
-<i>severity</i>). For example, you may want to see every debugging message
-of MSG while only being interested into the messages at level "error" or
-higher about the XBT internals.
-
-@subsection log_app Message appenders
-
-The message appenders are in charge of actually displaying the
-message to the user. For now, four appenders exist:
-- the default one prints stuff on stderr
-- file sends the data to a single file
-- rollfile overwrites the file when the file grows too large
-- splitfile creates new files with a specific maximum size
-
-@subsection log_lay Message layouts
-
-The message layouts are the elements in charge of choosing how each message
-will look like. Their result is a string which is then passed to the appender
-attached to the category to be displayed.
-
-For now, there is two layouts: The simple one, which is good for most cases,
-and another one allowing users to specify the format they want.
-@ref log_use_conf provides more info on this.
-
-@subsection log_hist History of this module
-
-Historically, this module is an adaptation of the log4c project, which is dead
-upstream, and which I was given the permission to fork under the LGPL licence
-by the log4c's authors. The log4c project itself was loosely based on the
-Apache project's Log4J, which also inspired Log4CC, Log4py and so on. Our work
-differs somehow from these projects anyway, because the C programming language
-is not object oriented.
-
-@section log_API C Programmer interface
-
-Please also refer to the @ref XBT_log "full API" for more information.
-
-@subsection log_API_cat Constructing the category hierarchy
-
-Every category is declared by providing a name and an optional
-parent. If no parent is explicitly named, the root category, LOG_ROOT_CAT is
-the category's parent.
-
-A category is created by a macro call at the top level of a file. A
-category can be created with any one of the following macros:
-
- - @ref XBT_LOG_NEW_CATEGORY(MyCat,desc); Create a new root
- - @ref XBT_LOG_NEW_SUBCATEGORY(MyCat, ParentCat,desc);
- Create a new category being child of the category ParentCat
- - @ref XBT_LOG_NEW_DEFAULT_CATEGORY(MyCat,desc);
- Like XBT_LOG_NEW_CATEGORY, but the new category is the default one
- in this file
- - @ref XBT_LOG_NEW_DEFAULT_SUBCATEGORY(MyCat, ParentCat,desc);
- Like XBT_LOG_NEW_SUBCATEGORY, but the new category is the default one
- in this file
-
-The parent cat can be defined in the same file or in another file (in
-which case you want to use the @ref XBT_LOG_EXTERNAL_CATEGORY macro to make
-it visible in the current file), but each category may have only one
-definition. Likewise, you can use a category defined in another file as
-default one using @ref XBT_LOG_EXTERNAL_DEFAULT_CATEGORY
-
-Typically, there will be a Category for each module and sub-module, so you
-can independently control logging for each module.
-
-For a list of all existing categories, please refer to the @ref XBT_log_cats
-section. This file is generated automatically from the SimGrid source code, so
-it should be complete and accurate.
-Also refer to the @ref XBT_log "full API" for more information.
-
-@subsection log_API_pri Declaring message priority
-
-A category may be assigned a threshold priority. The set of priorities are
-defined by the @ref e_xbt_log_priority_t enum. All logging request under
-this priority will be discarded.
-
-If a given category is not assigned a threshold priority, then it inherits
-one from its closest ancestor with an assigned threshold. To ensure that all
-categories can eventually inherit a threshold, the root category always has
-an assigned threshold priority.
-
-Logging requests are made by invoking a logging macro on a category. All of
-the macros have a printf-style format string followed by arguments. If you
-compile with the -Wall option, gcc will warn you for unmatched arguments, ie
-when you pass a pointer to a string where an integer was specified by the
-format. This is usually a good idea.
-
-Here is an example of the most basic type of macro. This is a logging
-request with priority <i>warning</i>.
-
-<code>XBT_CLOG(MyCat, xbt_log_priority_warning, "Values are: %d and '%s'", 5,
-"oops");</code>
-
-A logging request is said to be enabled if its priority is higher than or
-equal to the threshold priority of its category. Otherwise, the request is
-said to be disabled. A category without an assigned priority will inherit
-one from the hierarchy.
-
-It is possible to use any non-negative integer as a priority. If, as in the
-example, one of the standard priorities is used, then there is a convenience
-macro that is typically used instead. For example, the above example is
-equivalent to the shorter:
-
-<code>XBT_CWARN(MyCat, "Values are: %d and '%s'", 5, "oops");</code>
-
-@subsection log_API_isenabled Checking if a particular category/priority is enabled
-
-It is sometimes useful to check whether a particular category is
-enabled at a particular priority. One example is when you want to do
-some extra computation to prepare a nice debugging message. There is
-no use of doing so if the message won't be used afterward because
-debugging is turned off.
-
-Doing so is extremely easy, thanks to the XBT_LOG_ISENABLED(category, priority).
-
-@subsection log_API_subcat Using a default category (the easy interface)
-
-If @ref XBT_LOG_NEW_DEFAULT_SUBCATEGORY(MyCat, Parent) or
-@ref XBT_LOG_NEW_DEFAULT_CATEGORY(MyCat) is used to create the
-category, then the even shorter form can be used:
-
-<code>XBT_WARN("Values are: %s and '%d'", 5, "oops");</code>
-
-Only one default category can be created per file, though multiple
-non-defaults can be created and used.
-
-@subsection log_API_easy Putting all together: the easy interface
-
-First of all, each module should register its own category into the categories
-tree using @ref XBT_LOG_NEW_DEFAULT_SUBCATEGORY.
-
-Then, logging should be done with the #XBT_DEBUG, #XBT_VERB, #XBT_INFO,
-#XBT_WARN, #XBT_ERROR and #XBT_CRITICAL macros.
-
-Under GCC, these macro check there arguments the same way than printf does. So,
-if you compile with -Wall, the following code will issue a warning:
-<code>XBT_DEBUG("Found %s (id %d)", some_string, a_double)</code>
-
-If you want to specify the category to log onto (for example because you
-have more than one category per file, add a C before the name of the log
-producing macro (ie, use #XBT_CDEBUG, #XBT_CVERB, #XBT_CINFO, #XBT_CWARN,
-#XBT_CERROR and #XBT_CCRITICAL and friends), and pass the category name as
-first argument.
-
-The TRACE priority is not used the same way than the other. You should use
-the #XBT_IN, #XBT_OUT and #XBT_HERE macros instead.
-
-@subsection log_API_example Example of use
-
-Here is a more complete example:
-
-@verbatim
-#include "xbt/log.h"
-
-/ * create a category and a default subcategory * /
-XBT_LOG_NEW_CATEGORY(VSS);
-XBT_LOG_NEW_DEFAULT_SUBCATEGORY(SA, VSS);
-
-int main() {
- / * Now set the parent's priority. (the string would typically be a runtime option) * /
- xbt_log_control_set("SA.thresh:3");
-
- / * This request is enabled, because WARNING >= INFO. * /
- XBT_CWARN(VSS, "Low fuel level.");
-
- / * This request is disabled, because DEBUG < INFO. * /
- XBT_CDEBUG(VSS, "Starting search for nearest gas station.");
-
- / * The default category SA inherits its priority from VSS. Thus,
- the following request is enabled because INFO >= INFO. * /
- XBT_INFO("Located nearest gas station.");
-
- / * This request is disabled, because DEBUG < INFO. * /
- XBT_DEBUG("Exiting gas station search");
-}
-@endverbatim
-
-Please also refer to the @ref XBT_log "full API" for more information.
-
-@section log_user User interface
-
-@subsection log_use_conf Configuration
-
-Although rarely done, it is possible to configure the logs during
-program initialization by invoking the xbt_log_control_set() method
-manually. A more conventional way is to use the --log command line
-argument. xbt_init() (called by MSG_init() and friends)
-checks and deals properly with such arguments.
-
-@subsubsection log_use_conf_thres Threshold configuration
-
-The most common setting is to control which logging event will get
-displayed by setting a threshold to each category through the
-<tt>threshold</tt> keyword.
-
-For example, @verbatim --log=root.thresh:debug@endverbatim will make
-SimGrid <b>extremely</b> verbose while @verbatim
---log=root.thres:critical@endverbatim should shut it almost
-completely off.
-
-Note that the <tt>threshold</tt> keyword can be abbreviated here. For example,
-all the following notations have the same result.
-@verbatim
---log=root.threshold:debug
---log=root.threshold:debug
---log=root.thresho:debug
---log=root.thresh:debug
---log=root.thres:debug
---log=root.thre:debug
---log=root.thr:debug
---log=root.th:debug
---log=root.t:debug
---log=root.:debug <--- That's obviously really ugly, but it actually works.
-@endverbatim
-
-The full list of recognized thresholds is the following:
-
- - trace: enter and return of some functions
- - debug: crufty output
- - verbose: verbose output for the user wanting more
- - info: output about the regular functioning
- - warning: minor issue encountered
- - error: issue encountered
- - critical: major issue encountered
-
-@subsubsection log_use_conf_multi Passing several settings
-
-You can provide several of those arguments to change the setting of several
-categories, they will be applied from left to right. So,
-@verbatim --log="root.thres:debug root.thres:critical"@endverbatim should
-disable almost any logging.
-
-Note that the quotes on above line are mandatory because there is a space in
-the argument, so we are protecting ourselves from the shell, not from SimGrid.
-We could also reach the same effect with this:
-@verbatim --log=root.thres:debug --log=root.thres:critical@endverbatim
-
-@subsubsection log_use_conf_fmt Format configuration
-
-You can control the format of log messages through the <tt>fmt</tt>
-keyword. For example, @verbatim --log=root.fmt:%m@endverbatim reduces
-the output to the user-message only, removing any decoration such as
-the date, or the process ID, everything.
-
-Here are the existing format directives:
-
- - %%: the % char
- - %%n: platform-dependent line separator (LOG4J compatible)
- - %%e: plain old space (SimGrid extension)
-
- - %%m: user-provided message
-
- - %%c: Category name (LOG4J compatible)
- - %%p: Priority name (LOG4J compatible)
-
- - %%h: Hostname (SimGrid extension)
- - %%P: Process name (SimGrid extension -- note that with SMPI this is the integer value of the process rank)
- - %%t: Thread "name" (LOG4J compatible -- actually the address of the thread in memory)
- - %%i: Process PID (SimGrid extension -- this is a 'i' as in 'i'dea)
-
- - %%F: file name where the log event was raised (LOG4J compatible)
- - %%l: location where the log event was raised (LOG4J compatible, like '%%F:%%L' -- this is a l as in 'l'etter)
- - %%L: line number where the log event was raised (LOG4J compatible)
- - %%M: function name (LOG4J compatible -- called method name here of course).
-
- - %%d: date (UNIX-like epoch)
- - %%r: application age (time elapsed since the beginning of the application)
-
-
-If you want to mimic the simple layout with the format one, you would use this
-format: '[%%h:%%i:(%%i) %%r] %%l: [%%c/%%p] %%m%%n'. This is not completely correct
-because the simple layout do not display the message location for messages at
-priority INFO (thus, the fmt is '[%%h:%%i:(%%i) %%r] [%%c/%%p] %%m%%n' in this
-case). Moreover, if there is no process name (ie, messages coming from the
-library itself, or test programs doing strange things) do not display the
-process identity (thus, fmt is '[%%r] %%l: [%%c/%%p] %%m%%n' in that case, and '[%%r]
-[%%c/%%p] %%m%%n' if they are at priority INFO).
-
-For now, there is only two format modifiers: the precision and the
-width fields. You can for example specify %.4r to get the application
-age with 4 numbers after the radix, or %15p to get the process name
-on 15 columns. Finally, you can specify %10.6r to get the time on at
-most 10 columns, with 6 numbers after the radix.
-
-Note that when specifying the width, it is filled with spaces. That
-is to say that for example %5r in your format is converted to "% 5f"
-for printf (note the extra space); there is no way to fill the empty
-columns with 0 (ie, pass "%05f" to printf). Another limitation is
-that you cannot set specific layouts to the several priorities.
-
-@subsubsection log_use_conf_app Category appender
-
-You can control the appender of log messages through the <tt>app</tt>
-keyword. For example,
-@verbatim --log=root.app:file:mylogfile@endverbatim redirects the
-output to the file mylogfile.
-
-For splitfile appender, the format is
-@verbatim --log=root.app:splitfile:size:mylogfile_%.format@endverbatim
-
-The size is in bytes, and the % wildcard will be replaced by the number of the
-file. If no % is present, it will be appended at the end.
-
-rollfile appender is also available, it can be used as
-@verbatim --log=root.app:rollfile:size:mylogfile@endverbatim
-When the file grows to be larger than the size, it will be emptied and new log
-events will be sent at its beginning
-
-Any appender setup this way have its own layout format (simple one by default),
-so you may have to change it too afterward. Moreover, the additivity of the log category
-is also set to false to prevent log event displayed by this appender to "leak" to any other
-appender higher in the hierarchy. If it is not what you wanted, you can naturally change it
-manually.
-
-@subsubsection log_use_conf_add Category additivity
-
-The <tt>add</tt> keyword allows one to specify the additivity of a
-category (see @ref log_in_app). '0', '1', 'no', 'yes', 'on'
-and 'off' are all valid values, with 'yes' as default.
-
-The following example resets the additivity of the xbt category to true (which is its default value).
-@verbatim --log=xbt.add:yes@endverbatim
-
-@subsection log_use_misc Misc and Caveats
-
- - Do not use any of the macros that start with '_'.
- - Log4J has a 'rolling file appender' which you can select with a run-time
- option and specify the max file size. This would be a nice default for
- non-kernel applications.
- - Careful, category names are global variables.
- - When writing a log format, you often want to use spaces. If you don't
- protect these spaces, they are used as configuration elements separators.
- For example, if you want to remove the date from the logs, you want to pass the following
- argument on the command line. The outer quotes are here to protect the string from the shell
- interpretation while the inner ones are there to prevent simgrid from splitting the string
- in several log parameters (that would be invalid).
- @verbatim --log="'root.fmt:%l: [%p/%c]: %m%n'"@endverbatim
- Another option is to use the SimGrid-specific format directive \%e for
- spaces, like in the following.
- @verbatim --log="root.fmt:%l:%e[%p/%c]:%e%m%n"@endverbatim
-
-@section log_internals Internal considerations
-
-This module is loaded of macro black magic, and when it goes wrong,
-SimGrid studently loose its ability to explain its problems. When
-messing around this module, I often find useful to define
-XBT_LOG_MAYDAY (which turns it back to good old printf) for the time
-of finding what's going wrong. But things are quite verbose when
-everything is enabled...
-
-@subsection log_in_perf Performance
-
-Except for the first invocation of a given category, a disabled logging request
-requires an a single comparison of a static variable to a constant.
-
-There is also compile time constant, @ref XBT_LOG_STATIC_THRESHOLD, which
-causes all logging requests with a lower priority to be optimized to 0 cost
-by the compiler. By setting it to xbt_log_priority_infinite, all logging
-requests are statically disabled at compile time and cost nothing. Released executables
-<i>might</i> be compiled with (note that it will prevent users to debug their problems)
-@verbatim-DXBT_LOG_STATIC_THRESHOLD=xbt_log_priority_infinite@endverbatim
-
-Compiling with the @verbatim-DNLOG@endverbatim option disables all logging
-requests at compilation time while the @verbatim-DNDEBUG@endverbatim disables
-the requests of priority below INFO.
-
-@todo Logging performance *may* be improved further by improving the message
-propagation from appender to appender in the category tree.
-
-@subsection log_in_app Appenders
-
-Each category has an optional appender. An appender is a pointer to a
-structure which starts with a pointer to a do_append() function. do_append()
-prints a message to a log.
-
-When a category is passed a message by one of the logging macros, the category performs the following actions:
-
- - if the category has an appender, the message is passed to the
- appender's do_append() function,
- - if additivity is true for the category, the message is passed to
- the category's parent. Additivity is true by default, and can be
- controlled by xbt_log_additivity_set() or something like --log=root.add:1 (see @ref log_use_conf_add).
- Also, when you add an appender to a category, its additivity is automatically turned to off.
- Turn it back on afterward if it is not what you wanted.
-
-By default, only the root category have an appender, and any other category has
-its additivity set to true. This causes all messages to be logged by the root
-category's appender.
-
-The default appender function currently prints to stderr.
-
-*/
