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logging: use static buffer in nm_logging_all_domains_to_string()

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Don't create a heap allocated GString to hold the static
result of nm_logging_all_domains_to_string().

Instead, use a static buffer of the exactly required size.

The main reason to do this, is to get the exact size of
"_all_logging_domains_to_str" buffer. This is the upper
boundary for the size of a string buffer to hold all domain
names.
We will need that boundary in the next commit. The attractive
thing here is that we will have a unit-test failure if this
boundery no longer matches (--with-more-asserts). That means,
this boundary is guarded by unit tests and we don't accidentally
get it wrong when the domains change.

Also, take care to initialize the buffer in a thread-safe manner.
It's easy enough to get right, so there is no excuse for having
non-thread-safe code in logging.
This commit is contained in:
Thomas Haller 2019-05-14 12:56:44 +02:00
parent cc2553e871
commit 9cddb9f8bd
2 changed files with 45 additions and 9 deletions
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41
src/nm-logging.c
View file

@ -549,27 +549,50 @@ _domains_to_string (gboolean include_level_override,
return g_string_free (str, FALSE);
}
static char _all_logging_domains_to_str[273];
const char *
nm_logging_all_domains_to_string (void)
{
static GString *str;
static const char *volatile str = NULL;
const char *s;
if (G_UNLIKELY (!str)) {
again:
s = g_atomic_pointer_get (&str);
if (G_UNLIKELY (!s)) {
static gsize once = 0;
const LogDesc *diter;
gsize buf_l;
char *buf_p;
str = g_string_new (LOGD_DEFAULT_STRING);
if (!g_once_init_enter (&once))
goto again;
buf_p = _all_logging_domains_to_str;
buf_l = sizeof (_all_logging_domains_to_str);
nm_utils_strbuf_append_str (&buf_p, &buf_l, LOGD_DEFAULT_STRING);
for (diter = &domain_desc[0]; diter->name; diter++) {
g_string_append_c (str, ',');
g_string_append (str, diter->name);
nm_utils_strbuf_append_c (&buf_p, &buf_l, ',');
nm_utils_strbuf_append_str (&buf_p, &buf_l, diter->name);
if (diter->num == LOGD_DHCP6)
g_string_append (str, "," LOGD_DHCP_STRING);
nm_utils_strbuf_append_str (&buf_p, &buf_l, ","LOGD_DHCP_STRING);
else if (diter->num == LOGD_IP6)
g_string_append (str, "," LOGD_IP_STRING);
nm_utils_strbuf_append_str (&buf_p, &buf_l, ","LOGD_IP_STRING);
}
g_string_append (str, "," LOGD_ALL_STRING);
nm_utils_strbuf_append_str (&buf_p, &buf_l, LOGD_ALL_STRING);
/* Did you modify the logging domains (or their names)? Adjust the size of
* _all_logging_domains_to_str buffer above to have the exact size. */
nm_assert (strlen (_all_logging_domains_to_str) == sizeof (_all_logging_domains_to_str) - 1);
nm_assert (buf_l == 1);
s = _all_logging_domains_to_str;
g_atomic_pointer_set (&str, s);
g_once_init_leave (&once, 1);
}
return str->str;
return s;
}
/**

13
src/tests/test-general.c
View file

@ -108,6 +108,17 @@ test_nm_utils_ip6_address_clear_host_address (void)
/*****************************************************************************/
static void
test_logging_domains (void)
{
const char *s;
s = nm_logging_all_domains_to_string ();
g_assert (s && s[0]);
}
/*****************************************************************************/
static void
_test_same_prefix (const char *a1, const char *a2, guint8 plen)
{
@ -2180,6 +2191,8 @@ main (int argc, char **argv)
{
nmtst_init_with_logging (&argc, &argv, NULL, "ALL");
g_test_add_func ("/general/test_logging_domains", test_logging_domains);
g_test_add_func ("/general/nm_utils_strbuf_append", test_nm_utils_strbuf_append);
g_test_add_func ("/general/nm_utils_ip6_address_clear_host_address", test_nm_utils_ip6_address_clear_host_address);