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gmessages: Expose our default filtering as API

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This allows programs that want to change how log messages are printed,
such as gnome-terminal (gnome-terminal#42) and Flatpak, to override
the log-writer or the legacy log-handler without having to reimplement
the G_MESSAGES_DEBUG filtering logic.

Signed-off-by: Simon McVittie <smcv@collabora.com>
This commit is contained in:
Simon McVittie 2020-07-23 17:57:44 +01:00 committed by Philip Withnall
parent 10b0ece9d8
commit b17b537a7d
4 changed files with 148 additions and 26 deletions
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1
docs/reference/glib/glib-sections.txt
View File

@ -1485,6 +1485,7 @@ g_log_writer_journald
g_log_writer_standard_streams
g_log_writer_default
g_log_writer_default_set_use_stderr
g_log_writer_default_would_drop
<SUBSECTION Private>
g_log_structured_standard

119
glib/gmessages.c
View File

@ -127,7 +127,8 @@
* It is recommended that custom log writer functions re-use the
* `G_MESSAGES_DEBUG` environment variable, rather than inventing a custom one,
* so that developers can re-use the same debugging techniques and tools across
* projects.
* projects. Since GLib 2.68, this can be implemented by dropping messages
* for which g_log_writer_default_would_drop() returns %TRUE.
*
* ## Testing for Messages ## {#testing-for-messages}
*
@ -2617,6 +2618,95 @@ log_is_old_api (const GLogField *fields,
g_strcmp0 (fields[0].value, "1") == 0);
}
/*
* Internal version of g_log_writer_default_would_drop(), which can
* read from either a log_domain or an array of fields. This avoids
* having to iterate through the fields if the @log_level is sufficient
* to make the decision.
*/
static gboolean
should_drop_message (GLogLevelFlags log_level,
const char *log_domain,
const GLogField *fields,
gsize n_fields)
{
/* Disable debug message output unless specified in G_MESSAGES_DEBUG. */
if (!(log_level & DEFAULT_LEVELS) && !(log_level >> G_LOG_LEVEL_USER_SHIFT))
{
const gchar *domains;
gsize i;
domains = g_getenv ("G_MESSAGES_DEBUG");
if ((log_level & INFO_LEVELS) == 0 ||
domains == NULL)
return TRUE;
if (log_domain == NULL)
{
for (i = 0; i < n_fields; i++)
{
if (g_strcmp0 (fields[i].key, "GLIB_DOMAIN") == 0)
{
log_domain = fields[i].value;
break;
}
}
}
if (strcmp (domains, "all") != 0 &&
(log_domain == NULL || !strstr (domains, log_domain)))
return TRUE;
}
return FALSE;
}
/**
* g_log_writer_default_would_drop:
* @log_domain: (nullable): log domain
* @log_level: log level, either from #GLogLevelFlags, or a user-defined
* level
*
* Check whether g_log_writer_default() and g_log_default_handler() would
* ignore a message with the given domain and level.
*
* As with g_log_default_handler(), this function drops debug and informational
* messages unless their log domain (or `all`) is listed in the space-separated
* `G_MESSAGES_DEBUG` environment variable.
*
* This can be used when implementing log writers with the same filtering
* behaviour as the default, but a different destination or output format:
*
* |[<!-- language="C" -->
* if (g_log_writer_default_would_drop (log_level, log_domain))
* return G_LOG_WRITER_HANDLED;
* ]|
*
* or to skip an expensive computation if it is only needed for a debugging
* message, and `G_MESSAGES_DEBUG` is not set:
*
* |[<!-- language="C" -->
* if (!g_log_writer_default_would_drop (G_LOG_LEVEL_DEBUG, G_LOG_DOMAIN))
* {
* gchar *result = expensive_computation (my_object);
*
* g_debug ("my_object result: %s", result);
* g_free (result);
* }
* ]|
*
* Returns: %TRUE if the log message would be dropped by GLib's
* default log handlers
* Since: 2.68
*/
gboolean
g_log_writer_default_would_drop (GLogLevelFlags log_level,
const char *log_domain)
{
return should_drop_message (log_level, log_domain, NULL, 0);
}
/**
* g_log_writer_default:
* @log_level: log level, either from #GLogLevelFlags, or a user-defined
@ -2661,31 +2751,8 @@ g_log_writer_default (GLogLevelFlags log_level,
g_return_val_if_fail (fields != NULL, G_LOG_WRITER_UNHANDLED);
g_return_val_if_fail (n_fields > 0, G_LOG_WRITER_UNHANDLED);
/* Disable debug message output unless specified in G_MESSAGES_DEBUG. */
if (!(log_level & DEFAULT_LEVELS) && !(log_level >> G_LOG_LEVEL_USER_SHIFT))
{
const gchar *domains, *log_domain = NULL;
gsize i;
domains = g_getenv ("G_MESSAGES_DEBUG");
if ((log_level & INFO_LEVELS) == 0 ||
domains == NULL)
return G_LOG_WRITER_HANDLED;
for (i = 0; i < n_fields; i++)
{
if (g_strcmp0 (fields[i].key, "GLIB_DOMAIN") == 0)
{
log_domain = fields[i].value;
break;
}
}
if (strcmp (domains, "all") != 0 &&
(log_domain == NULL || !strstr (domains, log_domain)))
return G_LOG_WRITER_HANDLED;
}
if (should_drop_message (log_level, NULL, fields, n_fields))
return G_LOG_WRITER_HANDLED;
/* Mark messages as fatal if they have a level set in
* g_log_set_always_fatal().

3
glib/gmessages.h
View File

@ -244,6 +244,9 @@ GLogWriterOutput g_log_writer_default (GLogLevelFlags log_level,
GLIB_AVAILABLE_IN_2_68
void g_log_writer_default_set_use_stderr (gboolean use_stderr);
GLIB_AVAILABLE_IN_2_68
gboolean g_log_writer_default_would_drop (GLogLevelFlags log_level,
const char *log_domain);
/**
* G_DEBUG_HERE:

51
glib/tests/logging.c
View File

@ -139,6 +139,53 @@ test_default_handler_debug_stderr (void)
g_log ("foo", G_LOG_LEVEL_DEBUG, "6");
g_log ("bar", G_LOG_LEVEL_DEBUG, "6");
g_log ("baz", G_LOG_LEVEL_DEBUG, "6");
exit (0);
}
static void
test_default_handler_would_drop (void)
{
g_unsetenv ("G_MESSAGES_DEBUG");
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_ERROR, "foo"));
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_CRITICAL, "foo"));
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_WARNING, "foo"));
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_MESSAGE, "foo"));
g_assert_true (g_log_writer_default_would_drop (G_LOG_LEVEL_INFO, "foo"));
g_assert_true (g_log_writer_default_would_drop (G_LOG_LEVEL_DEBUG, "foo"));
g_assert_false (g_log_writer_default_would_drop (1<<G_LOG_LEVEL_USER_SHIFT, "foo"));
g_setenv ("G_MESSAGES_DEBUG", "bar baz", TRUE);
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_ERROR, "foo"));
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_CRITICAL, "foo"));
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_WARNING, "foo"));
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_MESSAGE, "foo"));
g_assert_true (g_log_writer_default_would_drop (G_LOG_LEVEL_INFO, "foo"));
g_assert_true (g_log_writer_default_would_drop (G_LOG_LEVEL_DEBUG, "foo"));
g_assert_false (g_log_writer_default_would_drop (1<<G_LOG_LEVEL_USER_SHIFT, "foo"));
g_setenv ("G_MESSAGES_DEBUG", "foo bar", TRUE);
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_ERROR, "foo"));
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_CRITICAL, "foo"));
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_WARNING, "foo"));
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_MESSAGE, "foo"));
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_INFO, "foo"));
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_DEBUG, "foo"));
g_assert_false (g_log_writer_default_would_drop (1<<G_LOG_LEVEL_USER_SHIFT, "foo"));
g_setenv ("G_MESSAGES_DEBUG", "all", TRUE);
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_ERROR, "foo"));
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_CRITICAL, "foo"));
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_WARNING, "foo"));
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_MESSAGE, "foo"));
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_INFO, "foo"));
g_assert_false (g_log_writer_default_would_drop (G_LOG_LEVEL_DEBUG, "foo"));
g_assert_false (g_log_writer_default_would_drop (1<<G_LOG_LEVEL_USER_SHIFT, "foo"));
exit (0);
}
@ -193,6 +240,9 @@ test_default_handler (void)
g_test_trap_subprocess ("/logging/default-handler/subprocess/0x400", 0, 0);
g_test_trap_assert_passed ();
g_test_trap_assert_stdout ("*LOG-0x400*message7*");
g_test_trap_subprocess ("/logging/default-handler/subprocess/would-drop", 0, 0);
g_test_trap_assert_passed ();
}
static void
@ -600,6 +650,7 @@ main (int argc, char *argv[])
g_test_add_func ("/logging/default-handler/subprocess/debug", test_default_handler_debug);
g_test_add_func ("/logging/default-handler/subprocess/debug-stderr", test_default_handler_debug_stderr);
g_test_add_func ("/logging/default-handler/subprocess/0x400", test_default_handler_0x400);
g_test_add_func ("/logging/default-handler/subprocess/would-drop", test_default_handler_would_drop);
g_test_add_func ("/logging/warnings", test_warnings);
g_test_add_func ("/logging/fatal-log-mask", test_fatal_log_mask);
g_test_add_func ("/logging/set-handler", test_set_handler);