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glib/glib/gmessages.h
Philip Withnall ac0b0c84f7 gmessages: Expand documentation on GLogWriterFunc chaining 
As prompted by Marc-Andre Lureau.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

https://bugzilla.gnome.org/show_bug.cgi?id=661926
2017-06-14 09:57:01 +01:00

624 lines
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/* GLIB - Library of useful routines for C programming
* Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/
/*
* Modified by the GLib Team and others 1997-2000. See the AUTHORS
* file for a list of people on the GLib Team. See the ChangeLog
* files for a list of changes. These files are distributed with
* GLib at ftp://ftp.gtk.org/pub/gtk/.
*/
#ifndef __G_MESSAGES_H__
#define __G_MESSAGES_H__
#if !defined (__GLIB_H_INSIDE__) && !defined (GLIB_COMPILATION)
#error "Only <glib.h> can be included directly."
#endif
#include <stdarg.h>
#include <glib/gtypes.h>
#include <glib/gmacros.h>
#include <glib/gvariant.h>
G_BEGIN_DECLS
/* calculate a string size, guaranteed to fit format + args.
*/
GLIB_AVAILABLE_IN_ALL
gsize g_printf_string_upper_bound (const gchar* format,
va_list args) G_GNUC_PRINTF(1, 0);
/* Log level shift offset for user defined
* log levels (0-7 are used by GLib).
*/
#define G_LOG_LEVEL_USER_SHIFT (8)
/* Glib log levels and flags.
*/
typedef enum
{
/* log flags */
G_LOG_FLAG_RECURSION = 1 << 0,
G_LOG_FLAG_FATAL = 1 << 1,
/* GLib log levels */
G_LOG_LEVEL_ERROR = 1 << 2, /* always fatal */
G_LOG_LEVEL_CRITICAL = 1 << 3,
G_LOG_LEVEL_WARNING = 1 << 4,
G_LOG_LEVEL_MESSAGE = 1 << 5,
G_LOG_LEVEL_INFO = 1 << 6,
G_LOG_LEVEL_DEBUG = 1 << 7,
G_LOG_LEVEL_MASK = ~(G_LOG_FLAG_RECURSION | G_LOG_FLAG_FATAL)
} GLogLevelFlags;
/* GLib log levels that are considered fatal by default */
#define G_LOG_FATAL_MASK (G_LOG_FLAG_RECURSION | G_LOG_LEVEL_ERROR)
typedef void (*GLogFunc) (const gchar *log_domain,
GLogLevelFlags log_level,
const gchar *message,
gpointer user_data);
/* Logging mechanism
*/
GLIB_AVAILABLE_IN_ALL
guint g_log_set_handler (const gchar *log_domain,
GLogLevelFlags log_levels,
GLogFunc log_func,
gpointer user_data);
GLIB_AVAILABLE_IN_2_46
guint g_log_set_handler_full (const gchar *log_domain,
GLogLevelFlags log_levels,
GLogFunc log_func,
gpointer user_data,
GDestroyNotify destroy);
GLIB_AVAILABLE_IN_ALL
void g_log_remove_handler (const gchar *log_domain,
guint handler_id);
GLIB_AVAILABLE_IN_ALL
void g_log_default_handler (const gchar *log_domain,
GLogLevelFlags log_level,
const gchar *message,
gpointer unused_data);
GLIB_AVAILABLE_IN_ALL
GLogFunc g_log_set_default_handler (GLogFunc log_func,
gpointer user_data);
GLIB_AVAILABLE_IN_ALL
void g_log (const gchar *log_domain,
GLogLevelFlags log_level,
const gchar *format,
...) G_GNUC_PRINTF (3, 4);
GLIB_AVAILABLE_IN_ALL
void g_logv (const gchar *log_domain,
GLogLevelFlags log_level,
const gchar *format,
va_list args) G_GNUC_PRINTF(3, 0);
GLIB_AVAILABLE_IN_ALL
GLogLevelFlags g_log_set_fatal_mask (const gchar *log_domain,
GLogLevelFlags fatal_mask);
GLIB_AVAILABLE_IN_ALL
GLogLevelFlags g_log_set_always_fatal (GLogLevelFlags fatal_mask);
/* Structured logging mechanism. */
/**
* GLogWriterOutput:
* @G_LOG_WRITER_HANDLED: Log writer has handled the log entry.
* @G_LOG_WRITER_UNHANDLED: Log writer could not handle the log entry.
*
* Return values from #GLogWriterFuncs to indicate whether the given log entry
* was successfully handled by the writer, or whether there was an error in
* handling it (and hence a fallback writer should be used).
*
* If a #GLogWriterFunc ignores a log entry, it should return
* %G_LOG_WRITER_HANDLED.
*
* Since: 2.50
*/
typedef enum
{
G_LOG_WRITER_HANDLED = 1,
G_LOG_WRITER_UNHANDLED = 0,
} GLogWriterOutput;
/**
* GLogField:
* @key: field name (UTF-8 string)
* @value: field value (arbitrary bytes)
* @length: length of @value, in bytes, or -1 if it is nul-terminated
*
* Structure representing a single field in a structured log entry. See
* g_log_structured() for details.
*
* Log fields may contain arbitrary values, including binary with embedded nul
* bytes. If the field contains a string, the string must be UTF-8 encoded and
* have a trailing nul byte. Otherwise, @length must be set to a non-negative
* value.
*
* Since: 2.50
*/
typedef struct _GLogField GLogField;
struct _GLogField
{
const gchar *key;
gconstpointer value;
gssize length;
};
/**
* GLogWriterFunc:
* @log_level: log level of the message
* @fields: (array length=n_fields): fields forming the message
* @n_fields: number of @fields
* @user_data: user data passed to g_log_set_writer_func()
*
* Writer function for log entries. A log entry is a collection of one or more
* #GLogFields, using the standard [field names from journal
* specification](https://www.freedesktop.org/software/systemd/man/systemd.journal-fields.html).
* See g_log_structured() for more information.
*
* Writer functions must ignore fields which they do not recognise, unless they
* can write arbitrary binary output, as field values may be arbitrary binary.
*
* @log_level is guaranteed to be included in @fields as the `PRIORITY` field,
* but is provided separately for convenience of deciding whether or where to
* output the log entry.
*
* Writer functions should return %G_LOG_WRITER_HANDLED if they handled the log
* message successfully or if they deliberately ignored it. If there was an
* error handling the message (for example, if the writer function is meant to
* send messages to a remote logging server and there is a network error), it
* should return %G_LOG_WRITER_UNHANDLED. This allows writer functions to be
* chained and fall back to simpler handlers in case of failure.
*
* Returns: %G_LOG_WRITER_HANDLED if the log entry was handled successfully;
* %G_LOG_WRITER_UNHANDLED otherwise
* Since: 2.50
*/
typedef GLogWriterOutput (*GLogWriterFunc) (GLogLevelFlags log_level,
const GLogField *fields,
gsize n_fields,
gpointer user_data);
GLIB_AVAILABLE_IN_2_50
void g_log_structured (const gchar *log_domain,
GLogLevelFlags log_level,
...);
GLIB_AVAILABLE_IN_2_50
void g_log_structured_array (GLogLevelFlags log_level,
const GLogField *fields,
gsize n_fields);
GLIB_AVAILABLE_IN_2_50
void g_log_variant (const gchar *log_domain,
GLogLevelFlags log_level,
GVariant *fields);
GLIB_AVAILABLE_IN_2_50
void g_log_set_writer_func (GLogWriterFunc func,
gpointer user_data,
GDestroyNotify user_data_free);
GLIB_AVAILABLE_IN_2_50
gboolean g_log_writer_supports_color (gint output_fd);
GLIB_AVAILABLE_IN_2_50
gboolean g_log_writer_is_journald (gint output_fd);
GLIB_AVAILABLE_IN_2_50
gchar *g_log_writer_format_fields (GLogLevelFlags log_level,
const GLogField *fields,
gsize n_fields,
gboolean use_color);
GLIB_AVAILABLE_IN_2_50
GLogWriterOutput g_log_writer_journald (GLogLevelFlags log_level,
const GLogField *fields,
gsize n_fields,
gpointer user_data);
GLIB_AVAILABLE_IN_2_50
GLogWriterOutput g_log_writer_standard_streams (GLogLevelFlags log_level,
const GLogField *fields,
gsize n_fields,
gpointer user_data);
GLIB_AVAILABLE_IN_2_50
GLogWriterOutput g_log_writer_default (GLogLevelFlags log_level,
const GLogField *fields,
gsize n_fields,
gpointer user_data);
/**
* G_DEBUG_HERE:
*
* A convenience form of g_log_structured(), recommended to be added to
* functions when debugging. It prints the current monotonic time and the code
* location using %G_STRLOC.
*
* Since: 2.50
*/
#define G_DEBUG_HERE() \
g_log_structured (G_LOG_DOMAIN, G_LOG_LEVEL_DEBUG, \
"CODE_FILE", __FILE__, \
"CODE_LINE", G_STRINGIFY (__LINE__), \
"CODE_FUNC", G_STRFUNC, \
"MESSAGE", "%" G_GINT64_FORMAT ": %s", \
g_get_monotonic_time (), G_STRLOC)
/* internal */
void _g_log_fallback_handler (const gchar *log_domain,
GLogLevelFlags log_level,
const gchar *message,
gpointer unused_data);
/* Internal functions, used to implement the following macros */
GLIB_AVAILABLE_IN_ALL
void g_return_if_fail_warning (const char *log_domain,
const char *pretty_function,
const char *expression) G_ANALYZER_NORETURN;
GLIB_AVAILABLE_IN_ALL
void g_warn_message (const char *domain,
const char *file,
int line,
const char *func,
const char *warnexpr) G_ANALYZER_NORETURN;
GLIB_DEPRECATED
void g_assert_warning (const char *log_domain,
const char *file,
const int line,
const char *pretty_function,
const char *expression) G_GNUC_NORETURN;
#ifndef G_LOG_DOMAIN
#define G_LOG_DOMAIN ((gchar*) 0)
#endif /* G_LOG_DOMAIN */
#if defined(G_HAVE_ISO_VARARGS) && !G_ANALYZER_ANALYZING
#ifdef G_LOG_USE_STRUCTURED
#define g_error(...) G_STMT_START { \
g_log_structured (G_LOG_DOMAIN, G_LOG_LEVEL_ERROR, \
"CODE_FILE", __FILE__, \
"CODE_LINE", G_STRINGIFY (__LINE__), \
"CODE_FUNC", G_STRFUNC, \
"MESSAGE", __VA_ARGS__); \
for (;;) ; \
} G_STMT_END
#define g_message(...) g_log_structured (G_LOG_DOMAIN, G_LOG_LEVEL_MESSAGE, \
"CODE_FILE", __FILE__, \
"CODE_LINE", G_STRINGIFY (__LINE__), \
"CODE_FUNC", G_STRFUNC, \
"MESSAGE", __VA_ARGS__)
#define g_critical(...) g_log_structured (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL, \
"CODE_FILE", __FILE__, \
"CODE_LINE", G_STRINGIFY (__LINE__), \
"CODE_FUNC", G_STRFUNC, \
"MESSAGE", __VA_ARGS__)
#define g_warning(...) g_log_structured (G_LOG_DOMAIN, G_LOG_LEVEL_WARNING, \
"CODE_FILE", __FILE__, \
"CODE_LINE", G_STRINGIFY (__LINE__), \
"CODE_FUNC", G_STRFUNC, \
"MESSAGE", __VA_ARGS__)
#define g_info(...) g_log_structured (G_LOG_DOMAIN, G_LOG_LEVEL_INFO, \
"CODE_FILE", __FILE__, \
"CODE_LINE", G_STRINGIFY (__LINE__), \
"CODE_FUNC", G_STRFUNC, \
"MESSAGE", __VA_ARGS__)
#define g_debug(...) g_log_structured (G_LOG_DOMAIN, G_LOG_LEVEL_DEBUG, \
"CODE_FILE", __FILE__, \
"CODE_LINE", G_STRINGIFY (__LINE__), \
"CODE_FUNC", G_STRFUNC, \
"MESSAGE", __VA_ARGS__)
#else
/* for(;;) ; so that GCC knows that control doesn't go past g_error().
* Put space before ending semicolon to avoid C++ build warnings.
*/
#define g_error(...) G_STMT_START { \
g_log (G_LOG_DOMAIN, \
G_LOG_LEVEL_ERROR, \
__VA_ARGS__); \
for (;;) ; \
} G_STMT_END
#define g_message(...) g_log (G_LOG_DOMAIN, \
G_LOG_LEVEL_MESSAGE, \
__VA_ARGS__)
#define g_critical(...) g_log (G_LOG_DOMAIN, \
G_LOG_LEVEL_CRITICAL, \
__VA_ARGS__)
#define g_warning(...) g_log (G_LOG_DOMAIN, \
G_LOG_LEVEL_WARNING, \
__VA_ARGS__)
#define g_info(...) g_log (G_LOG_DOMAIN, \
G_LOG_LEVEL_INFO, \
__VA_ARGS__)
#define g_debug(...) g_log (G_LOG_DOMAIN, \
G_LOG_LEVEL_DEBUG, \
__VA_ARGS__)
#endif
#elif defined(G_HAVE_GNUC_VARARGS) && !G_ANALYZER_ANALYZING
#ifdef G_LOG_USE_STRUCTURED
#define g_error(format...) G_STMT_START { \
g_log_structured (G_LOG_DOMAIN, G_LOG_LEVEL_ERROR, \
"CODE_FILE", __FILE__, \
"CODE_LINE", G_STRINGIFY (__LINE__), \
"CODE_FUNC", G_STRFUNC, \
"MESSAGE", format); \
for (;;) ; \
} G_STMT_END
#define g_message(format...) g_log_structured (G_LOG_DOMAIN, G_LOG_LEVEL_MESSAGE, \
"CODE_FILE", __FILE__, \
"CODE_LINE", G_STRINGIFY (__LINE__), \
"CODE_FUNC", G_STRFUNC, \
"MESSAGE", format)
#define g_critical(format...) g_log_structured (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL, \
"CODE_FILE", __FILE__, \
"CODE_LINE", G_STRINGIFY (__LINE__), \
"CODE_FUNC", G_STRFUNC, \
"MESSAGE", format)
#define g_warning(format...) g_log_structured (G_LOG_DOMAIN, G_LOG_LEVEL_WARNING, \
"CODE_FILE", __FILE__, \
"CODE_LINE", G_STRINGIFY (__LINE__), \
"CODE_FUNC", G_STRFUNC, \
"MESSAGE", format)
#define g_info(format...) g_log_structured (G_LOG_DOMAIN, G_LOG_LEVEL_INFO, \
"CODE_FILE", __FILE__, \
"CODE_LINE", G_STRINGIFY (__LINE__), \
"CODE_FUNC", G_STRFUNC, \
"MESSAGE", format)
#define g_debug(format...) g_log_structured (G_LOG_DOMAIN, G_LOG_LEVEL_DEBUG, \
"CODE_FILE", __FILE__, \
"CODE_LINE", G_STRINGIFY (__LINE__), \
"CODE_FUNC", G_STRFUNC, \
"MESSAGE", format)
#else
#define g_error(format...) G_STMT_START { \
g_log (G_LOG_DOMAIN, \
G_LOG_LEVEL_ERROR, \
format); \
for (;;) ; \
} G_STMT_END
#define g_message(format...) g_log (G_LOG_DOMAIN, \
G_LOG_LEVEL_MESSAGE, \
format)
#define g_critical(format...) g_log (G_LOG_DOMAIN, \
G_LOG_LEVEL_CRITICAL, \
format)
#define g_warning(format...) g_log (G_LOG_DOMAIN, \
G_LOG_LEVEL_WARNING, \
format)
#define g_info(format...) g_log (G_LOG_DOMAIN, \
G_LOG_LEVEL_INFO, \
format)
#define g_debug(format...) g_log (G_LOG_DOMAIN, \
G_LOG_LEVEL_DEBUG, \
format)
#endif
#else /* no varargs macros */
static void g_error (const gchar *format, ...) G_GNUC_NORETURN G_ANALYZER_NORETURN;
static void g_critical (const gchar *format, ...) G_ANALYZER_NORETURN;
static void
g_error (const gchar *format,
...)
{
va_list args;
va_start (args, format);
g_logv (G_LOG_DOMAIN, G_LOG_LEVEL_ERROR, format, args);
va_end (args);
for(;;) ;
}
static void
g_message (const gchar *format,
...)
{
va_list args;
va_start (args, format);
g_logv (G_LOG_DOMAIN, G_LOG_LEVEL_MESSAGE, format, args);
va_end (args);
}
static void
g_critical (const gchar *format,
...)
{
va_list args;
va_start (args, format);
g_logv (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL, format, args);
va_end (args);
}
static void
g_warning (const gchar *format,
...)
{
va_list args;
va_start (args, format);
g_logv (G_LOG_DOMAIN, G_LOG_LEVEL_WARNING, format, args);
va_end (args);
}
static void
g_info (const gchar *format,
...)
{
va_list args;
va_start (args, format);
g_logv (G_LOG_DOMAIN, G_LOG_LEVEL_INFO, format, args);
va_end (args);
}
static void
g_debug (const gchar *format,
...)
{
va_list args;
va_start (args, format);
g_logv (G_LOG_DOMAIN, G_LOG_LEVEL_DEBUG, format, args);
va_end (args);
}
#endif /* !__GNUC__ */
/**
* GPrintFunc:
* @string: the message to output
*
* Specifies the type of the print handler functions.
* These are called with the complete formatted string to output.
*/
typedef void (*GPrintFunc) (const gchar *string);
GLIB_AVAILABLE_IN_ALL
void g_print (const gchar *format,
...) G_GNUC_PRINTF (1, 2);
GLIB_AVAILABLE_IN_ALL
GPrintFunc g_set_print_handler (GPrintFunc func);
GLIB_AVAILABLE_IN_ALL
void g_printerr (const gchar *format,
...) G_GNUC_PRINTF (1, 2);
GLIB_AVAILABLE_IN_ALL
GPrintFunc g_set_printerr_handler (GPrintFunc func);
/**
* g_warn_if_reached:
*
* Logs a warning.
*
* Since: 2.16
*/
#define g_warn_if_reached() \
do { \
g_warn_message (G_LOG_DOMAIN, __FILE__, __LINE__, G_STRFUNC, NULL); \
} while (0)
/**
* g_warn_if_fail:
* @expr: the expression to check
*
* Logs a warning if the expression is not true.
*
* Since: 2.16
*/
#define g_warn_if_fail(expr) \
do { \
if G_LIKELY (expr) ; \
else g_warn_message (G_LOG_DOMAIN, __FILE__, __LINE__, G_STRFUNC, #expr); \
} while (0)
#ifdef G_DISABLE_CHECKS
/**
* g_return_if_fail:
* @expr: the expression to check
*
* Verifies that the expression @expr, usually representing a precondition,
* evaluates to %TRUE. If the function returns a value, use
* g_return_val_if_fail() instead.
*
* If @expr evaluates to %FALSE, the current function should be considered to
* have undefined behaviour (a programmer error). The only correct solution
* to such an error is to change the module that is calling the current
* function, so that it avoids this incorrect call.
*
* To make this undefined behaviour visible, if @expr evaluates to %FALSE,
* the result is usually that a critical message is logged and the current
* function returns.
*
* If G_DISABLE_CHECKS is defined then the check is not performed. You
* should therefore not depend on any side effects of @expr.
*/
#define g_return_if_fail(expr) G_STMT_START{ (void)0; }G_STMT_END
/**
* g_return_val_if_fail:
* @expr: the expression to check
* @val: the value to return from the current function
* if the expression is not true
*
* Verifies that the expression @expr, usually representing a precondition,
* evaluates to %TRUE. If the function does not return a value, use
* g_return_if_fail() instead.
*
* If @expr evaluates to %FALSE, the current function should be considered to
* have undefined behaviour (a programmer error). The only correct solution
* to such an error is to change the module that is calling the current
* function, so that it avoids this incorrect call.
*
* To make this undefined behaviour visible, if @expr evaluates to %FALSE,
* the result is usually that a critical message is logged and @val is
* returned from the current function.
*
* If G_DISABLE_CHECKS is defined then the check is not performed. You
* should therefore not depend on any side effects of @expr.
*/
#define g_return_val_if_fail(expr,val) G_STMT_START{ (void)0; }G_STMT_END
/**
* g_return_if_reached:
*
* Logs a critical message and returns from the current function.
* This can only be used in functions which do not return a value.
*/
#define g_return_if_reached() G_STMT_START{ return; }G_STMT_END
/**
* g_return_val_if_reached:
* @val: the value to return from the current function
*
* Logs a critical message and returns @val.
*/
#define g_return_val_if_reached(val) G_STMT_START{ return (val); }G_STMT_END
#else /* !G_DISABLE_CHECKS */
#define g_return_if_fail(expr) G_STMT_START{ \
if G_LIKELY(expr) { } else \
{ \
g_return_if_fail_warning (G_LOG_DOMAIN, \
G_STRFUNC, \
#expr); \
return; \
}; }G_STMT_END
#define g_return_val_if_fail(expr,val) G_STMT_START{ \
if G_LIKELY(expr) { } else \
{ \
g_return_if_fail_warning (G_LOG_DOMAIN, \
G_STRFUNC, \
#expr); \
return (val); \
}; }G_STMT_END
#define g_return_if_reached() G_STMT_START{ \
g_log (G_LOG_DOMAIN, \
G_LOG_LEVEL_CRITICAL, \
"file %s: line %d (%s): should not be reached", \
__FILE__, \
__LINE__, \
G_STRFUNC); \
return; }G_STMT_END
#define g_return_val_if_reached(val) G_STMT_START{ \
g_log (G_LOG_DOMAIN, \
G_LOG_LEVEL_CRITICAL, \
"file %s: line %d (%s): should not be reached", \
__FILE__, \
__LINE__, \
G_STRFUNC); \
return (val); }G_STMT_END
#endif /* !G_DISABLE_CHECKS */
G_END_DECLS
#endif /* __G_MESSAGES_H__ */
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